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Regenerative medicine: stem cells and the science of monstrosity
  1. M Cooper
  1. Correspondence to:
 Melinda Cooper
 Department of Sociology, Division of Society, Culture, Media and Philosophy, Macquarie University, NSW 2109, Australia;


The nineteenth century science of teratology concerned itself with the study of malformations or “monstrosities”, as they were then called. The first major contribution to the field was the work of Isidore Geoffroy Saint-Hilaire, Histoire Generale et Particulière des Anomalies de l’Organisation chez l’Homme et les Animaux, published in 1832, whose classifications formed the basis for the later experimental science of teratogeny, the art of reproducing monstrosities in animal embryos. In this article, I will argue that recent developments in the field of regenerative medicine can be situated in the tradition of teratological and teratogenic studies dating back to the nineteenth century. In particular, I will be interested in the historical link between studies in teratogenesis (the artificial production of teratomas) and stem cell research. Recent advances in stem cell research, I will suggest, return us to the questions that animated nineteenth century investigations into the nature of the monstrous or the anomalous. In the process, our most intuitive conceptions of “life itself” are undergoing a profound transformation.

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One of the more curious offspring of nineteenth century biology was the science of teratogeny—a science which concerned itself with the causal laws of malformations or monstrosities. Teratology grew out of the epigenetic tradition of the later eighteenth century and received its first comprehensive formulation in the biological philosophy of Étienne Geoffroy Saint-Hilaire. In 1822, Étienne issued a second volume to his major work, Philosophie Anatomique, in which he extended his inquiries to include the laws of anatomical composition involved in the production of human monstrosities.1 The second volume of the Philosophie Anatomique represented the first detailed work of classification specifically dedicated to malformations, and the first to place the study of monstrosity at the very centre of a larger philosophy of nature. In 1832, Étienne’s son, Isidore, published his three volume Traité de Tératologie, which systematised and extended upon his father’s founding work.2 It was Isidore who invented the term teratology and declared the science of monstrosity an autonomous and even foundational discipline within the larger field of morphological anatomy.

From its inception, the science of teratology was associated with the more ambitious project of producing artificial monstrosities through experimentation on animal embryos. Both Étienne and Isidore record various inconclusive efforts to reproduce monstrosities through the manipulation of fertilised chicken eggs. For more detail on these experiments see Appel T A and Oppenheimer J A.3,4 These experiments were later carried out with more success by Camille Dareste, who credited himself with the invention of the biotechnological art of teratogeny, the experimental counterpart to teratology. Dareste’s 1871 work, Recherches sur la Production Artificielle des Monstruosités ou, Essais de Tératogénie Expérimentale, details experiments in which he set about producing all of the monstrosities listed by the teratologists and raises the possibility of creating wholly new varieties.5

The teratological tradition carried on into the twentieth century, but its conceptual relation to the problem of monstrosity was more often than not forgotten. “Today teratology is simply the science that deals with abnormal development and congenital malformations, without reference to ‘monstrosities,’ and is the one [definition] accepted by the biomedical world”.6 In this article, I will argue that recent developments in the field of regenerative medicine can be situated in the tradition of teratological and teratogenic studies dating back to the nineteenth century. In particular, I will be interested in the historical link between studies in teratogenesis (the artificial production of teratomas) and stem cell research. Recent advances in stem cell research, I will suggest, return us to the questions that animated nineteenth century investigations into the nature of the monstrous or the anomalous. In the process, our most intuitive conceptions of “life itself” are undergoing a profound transformation.


Perhaps the most comprehensive study of nineteenth century conceptions of the normal, the pathological, and the monstrous can be found in the work of the philosopher of science, Georges Canguilhem. In two texts, The Normal and the Pathological and “Monstrosity and the Monstrous”, Canguilhem situates the science of teratology within the larger historical context of biomedical approaches to the pathological.7,8

For Canguilhem, the most important innovation of the nineteenth century life sciences lies in the radical negation of any positive, irreducible concept of pathology, sickness or monstrosity. In a study of the work of Auguste Comte and Claude Bernard, he traces the formation of a theory of physiology according to which “the pathological phenomena found in living organisms are nothing more than quantitative variations [of the norm], greater or lesser according to corresponding physiological phenomena” (Canguilhem G,7 p 13). The normative bias of nineteenth century biology denied any qualitative specificity to the pathological. Illness and health could no longer be figured as two essentially hostile, incompatible forces, but came to be identified as mere quantitative variations in a continuum of biological phenomena all subject to the same physiological laws. As a consequence, the pathological became strictly measurable; it was located in any physiological phenomenon differing in intensity, by excess or default, from the normal state.

In the work of Auguste Comte, the qualitative identification of sickness and health was derived from Broussais’s theory of excitation, where disease was defined as “the excess or lack of excitation in the various tissues above or below the degree established as the norm” (Canguilhem G,7 p 17). In the work of the physiologist Claude Bernard, this reduction of the pathological to a variation on the normal was integrated into a homeostatic model of the organism. For Bernard, the various processes of organic metabolism were conditional upon a complex system of internal regulative mechanisms, normally tending towards equilibrium. The Bernardian principle of organic self regulation led to the formulation of a therapeutic science, whose aim was essentially restorative. If the pathological could be measured in so far as it produced disequilibrium, the therapeutic intervention of the medical sciences could only seek to re-establish those homeostatic mechanisms that had momentarily been disturbed by illness.9

In the conclusion to his study on the normal and the pathological, Canguilhem argues that one of the consequences of nineteenth century biology, in its attempt to reduce the pathological to a mere quantitative difference, was a tendency to eradicate the experience of illness itself:

The need to re-establish continuity in order to gain more knowledge for more effective action is such that the concept of disease would finally vanish. The conviction that one can scientifically restore the norm is such that in the end it annuls the pathological (Canguilhem G,7 p 13).

At the same time, and for the very same reason, he contends, the experimental study of pathological phenomena, ranging from illness to monstrosities or deformities, acquired an unprecedented importance as a means of illuminating the science of health.

In the life sciences of the nineteenth century, pathological phenomena came to operate as a kind of in vivo experimental confirmation, by default, of the operations of the norm. It is in this sense, Canguilhem argues, that the science of teratology, although ostensibly engaged in the investigation of monstrosities, actually exploited these models as a kind of experimental demonstration of the theory of biological normativity. In the work of Comte—for example, the study of pathology in the form of deformities or monstrosities can be understood as an extreme but perfectly logical extension of the study of illness. Monstrosities were perhaps more radical deviations from the norm, but they could only be understood and exploited in its shadow:

the study of anomalies and monstrosities conceived as both older and less curable illnesses completes the study of diseases: the “teratological approach” [study of monsters] is added to the “pathological approach” in biological investigation (Canguilhem G,7 p 20).

But Canguilhem’s rather schematic interpretation of nineteenth century biology does not seem to do justice to the alternative conceptions of the monstrous which coexisted with, and seriously undermined, the normative precepts of Bernardian science. This is particularly evident in his cursory treatment of the father and son, Étienne and Isidore Geoffroy Saint-Hilaire, who can be credited with founding the nineteenth century science of monstrosity. In a text devoted to the history of the monstrous—for example, Canguilhem notes that the science of teratology can be traced back to Étienne Geoffroy Saint-Hilaire’s occasional texts on monstrosity but received its most definitive formulation in his son Isidore’s major work of classification, Histoire Générale et Particulière des Anomalies de l’Organisation chez l’Homme et les Animaux. It is to this text that he attributes the final domestication of the monstrous. Hereafter, he argues, earlier notions of the monstrous, with their bizarre alliance of the fantastic and the medical, gave way to a strictly normative understanding of the relationship between the normal and the pathological:

Hereafter, monstrosity appears to have given up the secret of its causes and laws; the anomaly, it appears, is called upon to provide the explanation of the formation of the normal. Not because the normal is only an attenuated form of the pathological, but because the pathological is the normal that has been hindered or pushed off course. Take away the hindrance and you obtain the norm (Canguilhem G,8 pp 180–1).

Canguilhem’s work on the normal and the pathological has exerted an unmistakable influence over subsequent studies on the subject of monstrosity in the life sciences. In particular, his thesis that the invention of teratology as an autonomous scientific field represents a move towards a causal philosophy of the monstrous and hence a definitive act of normalisation, a kind of scientific disciplining of the irrational forces of the maternal imagination, has been corroborated by all but a few studies. One of the most influential of these is that of Marie-Hélène Huet, Monstrous Imagination,10 which uncritically adopts Canguilhem’s views on the nineteenth century concept of the monstrous (Huet M-H,10 pp 101–2).

It is precisely on this point, however, that I would question Canguilhem’s historical account. In the life sciences of the early nineteenth century, the precise nature of the monstrous was an object of unresolved debate, where the most normative conceptions of life came into conflict with the most anomalous. Étienne Geoffroy Saint-Hilaire’s theory of material composition depends precisely on a concept of the “anomalous” as an autonomous generative principle, ontologically prior to the distinction between the normal and the pathological.

The work of both Étienne and Isidore Geoffroy Saint-Hilaire represents a countertradition within the life sciences of the nineteenth century, a counterphilosophy of the monstrous which points to recent directions in the field of stem cell research.


In the early years of the nineteenth century, Étienne Geoffroy Saint-Hilaire was famous for having elaborated a philosophy of anatomy which refused to draw on analogies of form and function in the classification of animals. Instead, he developed a method of comparative morphology which relied on the principle of unity of composition—the idea that the differences and proximities between living structures should be understood as so many actualisations of the one, common plane of composition. For Étienne Geoffroy Saint-Hilaire, the point was not to determine the ideal form or function of an organism, from whence to deduce its possible deviations or monstrous anomalies, but rather to search for the geometrical principles of composition themselves, in all their possibilities. In other words, Geoffroy Saint-Hilaire taught that all possible structures could be related to each other through varying degrees of transformation. All variations of form, he argued, participated in the one abstract “plane of composition”, the one topological space of infinitely deformable relations. It follows that the normative distinction between the normal and the pathological is strictly incomprehensible within the terms of Geoffroy Saint-Hilaire’s philosophy. Étienne’s son, Isidore Geoffroy Saint-Hilaire, clarified this point when he distinguished between the abnormal and what he referred to as the “anomalous”—whereas the abnormal represents a deviation from the norm, a difference that can only be defined negatively in relation to the norm, the anomalous belongs to an order of abstract composition which precedes the very distinction between the normal and the pathological (Geoffroy Saint-Hilaire I,2 pp 56–7). Étienne argued that what are known as monstrosities represent varying degrees of transformation in the material structure of an organism—in this, they are no different from the bodies we call normal. Because, however, they materialise in non-habitual postures which may occur in the early stages of embryogenesis but are not often visible in the later stages of development, he accords them a special pedagogical value. A report on his work carried out by the Royal French Academy of Science, which is cited in Cahn T, recounts that:

Ever since Monsieur Geoffroy Saint-Hilaire was led to consider facts relative to monsters as so many experiments, as it were, prepared in advance by nature in order to show physiologists the means which give rise to organic compositions, he has continued to carry out research on these deviations of organisation. In effect, according to the author, the study of organisation in its irregular acts, and of nature caught as it were by surprise in moments of hesitation and impotence, offers a very instructive spectacle. Whoever, he adds, has taken stock of all the possible modifications of organisation, recognises that the diverse forms in which it manifests itself derive from the same type; he therefore does not regard these monsters, as Aristotle did, as exceptions to general laws, nor does he believe, like Pliny, that nature produces them to astonish us and have fun, rather he considers them as unfinished sketches, as representing differing degrees of organisation.11

Between 1821 and 1830, Étienne published thirty articles on the subject of monstrosity. For an overview and bibliography of these articles see Cahn T’s La Vie et l’Oeuvre de Étienne Geoffroy Saint-Hilaire (Cahn T,11 pp 167–85, 296–310). But the most extensive exposition and development of Étienne’s theses on monstrosity can be found in the later work of his son, Isidore, Histoire Générale et Particulière des Anomalies de l’Organisation chez l’Homme et les Animaux, des Monstruosités, des Varietés et Vices de Conformation, ou Traité de Tératologie, published in 1832.2

In particular, Isidore developed his father’s intuition that there existed a crucial relationship between the morphological plasticity of the early embryo and the strange contortions to be seen in the body of the monstrosity.

Isidore argued that the transformative power of composition of the anomalous is most visible, in developmental terms, in the very early stages of embryogenesis. The embryo traverses transformations at a speed which we are barely able to apprehend, and simultaneously embodies states which will become mutually exclusive in the later development of the fetus. Here he points to the coexistence of the male and female sexual organs in the early stages of embryogenesis and to the mutations of form which seem to fleetingly materialise the shapes of other species. In the very early stages of development, it seems, the different possibilities of composition which will later be defined in restrictive terms as so many mutually exclusive paths of differentiation, are able to coexist.

Drawing on his father’s work on arrested and retarded development, Isidore Geoffroy Saint-Hilaire accounted for monstrosities as a stage of embryonic development which had become suspended in time or lagged behind the rest of the body. The organs and functions which would later be differentiated in the progressive unfolding of development had here been freeze framed in an incongruous coexistence of the embryonic and the mature. Monstrosities, he concluded, offer us a material insight into the transformative possibilities of the anomalous. They represent not so much a deviation from the norm but rather the partial actualisation of another order of composition altogether—the anomalous:

Up until then, the phenomena of monstrosity had been considered as nothing more than irregular arrangements, bizarre and disordered formations; vain spectacle by which nature amused itself by making fun of its observers and liberating itself from its ordinary laws. [The theory of philosophical anatomy] replaces the idea of bizarre, irregular beings with the truer, more philosophical one of beings obstructed in their development, where organs of the embryonic stage, preserved until birth, have come to be associated with organs of the fetal stage. Monstrosity is no longer a blind disorder, but another, equally regular, equally lawful order; or rather, if one prefers, it is the mixture of a former order and a new order, the simultaneous presence of two states which, ordinarily, succeed one another (Geoffroy Saint-Hilaire I,2 p 18).

It is also because of their mutual participation in the powers of composition of the “anomalous” that Geoffroy Saint-Hilaire predicts the future interdependence between studies in embryology and teratology. All monstrosities, he claims, are to some degree “permanent embryos”, living anachronisms that preserve as if suspended in time the stages of early embryological development:

From this moment too, the science of monstrosities is intimately linked to anatomy, and especially with that branch of anatomy which is concerned with the laws of development and the order of appearance of our organs. Monsters, according to the new theory, are in some respects permanent embryos; they show us the emergence of simple organs just as in the first days of their formation; as if nature had halted its course in order to provide our too slow observation with the time and means to apprehend it. In the future, therefore, the science of monstrosity cannot be separated from embryogenesis; it will usefully contribute to its progress and will receive no less considerable services in return (Geoffroy Saint-Hilaire I,2 p 19).

It is not surprising then that Isidore reserves a special place for what he calls parasitic monstrosities—embryonic growths that can remain indefinitely within their mother’s body, in the ovaries or uterus, sprouting hair, fatty tissue, teeth, and cartilage in a strange living caricature of the normal embryo. Isidore approaches the parasitic monster with an unmistakable sense of fascination. He readily admits that medical science offers little insight into these monstrosities, often considered as mere waste products, and yet he dedicates over thirty pages to their description and places them at the very end of his list of developmental anomalies because, in his opinion, they represent the most anomalous of growths:

Anatomists have long been aware that we sometimes find, either in the uterus or the ovaries or even in some other part of the body, diverse organic parts such as teeth or even varying amounts of bone, held together in a very irregular and often totally formless mass. The history of these singular productions has remained very obscure; and perhaps their complete explication will continue to elude the explanations of physiologists for a long time to come. However, even now it is possible to demonstrate, as we shall see, that at least in some cases, these organic parts which have developed in the uterus or ovaries are nothing but products of conception that have remained singularly imperfect, new beings whose formation, initiated or subject very early on to the influence of very anomalous circumstances, has been powerfully obstructed or diverted in a very warped direction (Geoffroy Saint-Hilaire I,2 pp 536–7).

Firstly and most obviously, parasitic monstrosities are anomalous from a morphological point of view. Although they grow and differentiate—Geoffroy Saint-Hilaire lingers over the details of sprouting hair and sets of teeth—they never acquire the regular morphological form of the organic body. Indeed, he comments, they are not so much bodies as clusters of tissue. Their form is strictly speaking “indeterminable”:

Not only does their form deviate considerably from the common type but it is absolutely indeterminable. Their cluster [ensemble]—for body is hardly a word that can be applied to these confused masses—is composed only of a few organic parts, mostly a few bones or teeth in various groupings, often accompanied by fat and hair, and adhering, without the intermediary of an umbilical cord, to the organs of the mother, or perhaps sometimes in a few cases to a very imperfect and more or less completely unrecognisable placenta (Geoffroy Saint-Hilaire I,2 p 537–p 8).

More obscurely, Geoffroy Saint-Hilaire points to evidence suggesting that the parasitic monster does not necessarily have to die. All monstrosities, he contends, can be considered to some degree as “permanent embryos”, embodying frozen moments of early embryological development. The parasitic monster, however, reveals the extreme potentialities of the anomalous in the sense that it appears capable of “prolonging almost indefinitely its life in the womb of its mother” (Geoffroy Saint-Hilaire I,2 p 564). The parasitic monster is the product of a pregnancy that never comes to term, an interminable and bizarrely disorganised gestation:

In relation to the mother, they therefore remain as young embryos; and as this latent and completely embryonic life is sufficient for such simple beings, they are neither expelled from the uterus, if they have developed in this organ, nor, if they have formed in the ovaries, tubes or abdomen, do they perish as a result of ineffectual birth spasms, just like those extrauterine fetuses which do not succumb in the first months.

Parasitic monsters are thus permanent embryos whose gestation has no term (Geoffroy Saint-Hilaire I,2 p 564).

What Isidore Geoffroy Saint-Hilaire is describing here is a type of ovarian tumour which would come to be known as a teratoma in the latter part of the nineteenth century (the term teratoma, which literally means monster tumour, was first coined in 1863). For a detailed history of the teratoma, see History of teratomas by J E Wheeler.12 Teratomas have a long medical history. Fragmentary accounts of visible teratomas (in the testes or the spine of newborn infants) can be found in ancient tablets. The first well documented case of an ovarian teratoma can be traced back to the seventeenth century, when the dissection of corpses had become commonplace. A medical text published in 1658 describes and illustrates an ovarian teratoma sprouting a clump of hair.13 In the nineteenth century, reports of ovarian tumours, containing lurid details of teeth, weight and hair, became more frequent. The genesis of teratomas, however, remained controversial. Once thought to arise from nightmares or communion with witches or the devil, teratomas retained a connection with perverse sexuality in the medical accounts of the nineteenth century. Geoffroy Saint-Hilaire—for example, cites contemporary theories attributing the parasitic monster to excessive masturbation—such theories were able to account for the existence of parasitic monsters in virgin or prepubescent girls and old women. Because Geoffroy Saint-Hilaire insists, however, on attributing them to a “veritable act of generation” involving fertilisation, he excludes these cases from his overview (Geoffroy Saint-Hilaire I,2 pp 556–60). Parasitic monsters, he argues, must be considered as true products of conception.

It was not until the latter part of the twentieth century that biologists returned to the question of the genesis of teratomas, in the context of investigations into germ cell development, differentiation, and cancer. It was these studies that established a link between ovarian teratomas and parthenogenesis—confirming Geoffroy Saint-Hilaire’s thesis that the teratoma is indeed the product of a “veritable act of generation”, but one which does not involve the union of egg and sperm. It was from these studies also that the contemporary field of stem cell research emerged. The history of stem cells, in other words, can be traced back to experiments in teratogenesis—the artificial production of “monstrous” growths in animals.

In what follows, I will look at the teratogenic experiments which emerged from Étienne and Isidore Geoffroy Saint-Hilaire’s founding work on teratology, and suggest a conceptual affiliation between these early experiments in the production of monstrosities and the recent history of stem cell research.


In his 1871 work, Recherches sur la Production Artificielle des Monstruosités ou, Essais de Tératogénie Expérimentale,5 Camille Dareste, the founder of the experimental science of teratogeny, expresses his intellectual debt to Étienne and Isidore Geoffroy Saint-Hilaire, the first anatomists to have systematically studied the question of monstrosity.

In Dareste’s work, however, there is a shift in perspective. Whereas Étienne and Isidore Geoffroy Saint-Hilaire were interested in the infinite possibilities of transformation which exist in virtual form in the abstract plane of composition underlying all material structures, Dareste looks towards the future evolution of life, in which these transformations will unfold as so many new, unpredictable inventions. For Dareste, the anomalous is not so much an ontological principle as a time arrow of innovation (although of course the two perspectives are not mutually exclusive). He conceives of evolution as an expanding horizon of variability, an open ended exploration of the possibilities of life, in which the experimental science of teratogeny participates:

Whereas observation only gives us a knowledge of actual realities, experimentation, thanks to its creative power, realises all that is possible; it thus opens up unlimited prospects (Dareste C,5 p 42).

Like experimental chemistry, he claims, teratogeny should aspire to become a “science of all possible bodies,” implying an “unlimited variability” of forms (Dareste C,5 p 24–p 43). His interest in the time arrow of evolution implies that the unlimited prospects of biological invention can no longer be deduced in the present, from the transformative possibilities inherent in all material structures, but can only be revealed in the future. In this sense, he questions whether suspended, arrested or excessive development account for all the possibilities of invention. Pointing to the phenomenon of metamorphosis in insects, he asks whether such dramatic reinventions of structure might be possible in vertebrates:

Are arrested and excessive development the only modifications that an organ can undergo? And isn’t it possible to conceive that an embryonic blastomere might, in the course of its evolution, acquire a form and a structure that are completely different from the one it presents in its normal state? (Dareste C,5 p 200)

Dareste’s provisional response is that given the current underdeveloped state of experimental studies, “it is impossible to establish in any definitive way the limits of the possible” (Dareste C,5 p 202).

Writing in the latter part of the nineteenth century when Darwin’s work had become available, but prior to the later split between embryology and Mendelian genetics, Dareste was able to draw connections between the teratological tradition and the Darwinian concept of inheritable variation. He quite explicitly presented his own teratological experiments as an extension of Darwin’s studies on plant hybridisation and thus as a means of illuminating and even initiating the formation of new species and races from the production of monstrosities:

It [my research] demonstrates in the most complete manner the possibility of modifying, by the action of external physical causes, the evolution of a fertilised germ. The demonstration of this fact is of interest not only for the production of monsters but also for biology in its entirety.

In effect, if it is possible to produce monstrosities by modifying the evolution of a fertilised germ, we must consider it possible to produce simple varieties, in other words slight deviations from the specific type, which are compatible with life and the generative functions (Dareste C,5 p 41, p 42).

For Darwin, as for Étienne and Isidore Geoffroy Saint-Hilaire, although informed by different perspectives, anomalous variation represented the very possibility of invention, without which life would be incapable of transformation or evolution. Darwin after all insisted that “monstrosities cannot be separated by any distinct line from slighter variations” and established their difference as one of utility only.14 “Monstrosity”, according to Darwin, implies “some considerable deviation of structure, generally injurious, or not useful to the species”, and by extension we could define his concept of variation as entailing the production of a useful or reproducible monstrosity—a monstrosity that works (Darwin C,14 p 34). The significance of this passage in relation to social conceptions of the normal and pathological, has been analysed at length by the cultural historian E O’Neill in her study, Raw Material: Producing Pathology in Victorian Culture.15 O’Neill argues that scientific discourses of the monstrous were fundamentally distinct from the more familiar discourses of degeneration which flourished in the nineteenth century. Whereas the science of degeneration was closely associated with notions of racial and social hygiene and focused on the deformities of the labouring body, the science of monstrosity presented the body as public spectacle, novel commodity, and innovation. In this sense, if the institutional context of the degenerate or abnormal body can be traced from the clinic, to the school and to the factory, and identified with the mechanisms of discipline, as analysed by Foucault, O’Neill argues that the monstrous body could be found simultaneously in the public science lecture, where deformities were put on display, and on stage in the freak show. Far from attempting a normalisation of the degenerate, she contends that the freak show presented the anomalous in its productive, regenerative, and even sublime possibilities.

The popularity of the freak show may have been a sign of cultural degeneration, but the freaks themselves were, paradoxically, an allegory for the regenerative possibilities contained within the spectacle of decline. Indeed, what the freak show celebrates is a marvellously debased image of industrial existence, a mode of being so phenomenally degraded that it approaches the sublime. Monstrosity does not register defect as disease; instead it makes human aberration into an advertisement for a new embodiment (O’Neill E,15 p 193).

The result was a sort of assembly-line individualism, an endless procession of human oddities whose cumulative impact was to standardize abnormality itself, to reduce the scene of nature’s bounty to a series of predictable, replaceable originals (O’Neill E,15 p 195).

In accord with O’Neill’s thesis, my reading of the science of teratology suggests that it offers a conception of the anomalous as prior to the normal, and reproducible as such.

Throughout the Origin of Species, Darwin freely cites examples from Geoffroy Saint-Hilaire’s classification of embryological monstrosities and in the French version of the Descent of Man, he refers to Dareste’s experiments as “full of promise for the future”. For Darwin’s references to Geoffroy Saint-Hilaire, see The Origin of Species (Darwin C,14 p 115, p 118, p 122). For Darwin’s remarks on Dareste, as cited by Dareste himself, see Dareste’s 1871 work, (Dareste C,5 p 46). Dareste, however, seems to be putting forward a Lamarckian theory of acquired inheritance when he writes that “the heredity of all varieties of organisation, when they do not impede the exercise of the generative functions, is now established in the clearest of manners. It is the condition of the formation of races” (Dareste C,5 p 41). The Lamarckian theory of heredity was later discredited by the Neo-Darwinian school, which restricted inheritable variation to chance genetic mutations. But in the context of current biotechnological experiments it could be argued that we are returning to a Neo-Lamarckian model in which acquired transformation becomes inheritable.

Certainly, Dareste’s reflections on the future possibilities of teratogeny are remarkably prescient. He noted that his own experiments intervened in the process of embryogenesis after fertilisation while Darwin’s studies on plant selection consisted in the determination of particular crosses before fertilisation. Neither of these methods, however, had as yet developed ways of intervening into the germ cell (unfertilised egg or sperm) itself (Dareste C,5 p 42 note 1). It was in this direction, he suggested, that experiments would need to move if the production of monstrosity was to become a truly generative science—a science, in other words, in which monstrosity would be put to work as the source of “all possible bodies”.

Recent studies on stem cells have indeed emerged from the intersection of these two lines of inquiry. In the first place, stem cell research developed from the experiments in teratogenesis—the artificial production of teratomas in mice. More recently, advances in cloning technologies have made it possible to cultivate reproducible forms of the same experimental “monstrosities”, effectively combining intervention into the germ cell with the manipulation of embryogenesis. This technique, known as somatic cell nuclear transfer, would involve a patient donating a somatic or non-reproductive cell which would then be cloned using an enucleated donor egg. The donor would effectively become the contemporary of his or her own (cloned) embryogenesis. The growth of this embryo would be deliberately deregulated in order to produce specific cell types, which would then be available to the patient as a reserve of therapeutic tissue. Such a technique combines the teratogenic experiments of Dareste with interventions into the actual germ cell to create something that could be likened to a reproducible monstrosity. For further detail on this technique, see Pederson RA.16

It is his interest in the experimental and controlled reproduction of monstrosity which establishes Dareste as a link between the science of teratology and recent advances in the field of “regenerative medicine”. Like Darwin, who defined the difference between variation and monstrosity in terms of their ability to perform work, Dareste’s approach to monstrosity is directly concerned with the problematic of their technical reproducibility—the problem which of course underlies the massive development of genetic and other biotechnologies over the last few decades. He described his experiments as an exercise in “zootechnics” and planned to move on to the mass reproduction of whole races of monstrosities (Dareste C,5 p 42).


Most accounts of the history of stem cell research tell us that embryonic stem (ES) cells were first discovered, or rather isolated and characterised in 1981. But the history of ES cells can be traced back two decades earlier to studies on teratogenesis (the production of embryonal tumours) in mice. Embryonic stem cells were first identified by the scientist Leroy Stevens in the course of his investigations into teratomas and related cancers called teratocarcinomas. On this point see Lewis R, Shostak S, and Stevens LC.17–19

From the very beginning, then, definitions of ES cells have been inextricably entangled with the monstrous properties of teratomas, teratocarcinomas and parthenogenetic growth. The question of their precise relationship to immortal, cancerous cells has recently returned to the fore of scientific debate.

Embryonal tumours are cancers which develop without any alteration in the cell’s genetic material. Tumours of this kind usually occur in the ovary or the testis and are derived from the germ cells. The more common ovarian teratoma results from a process of spontaneous parthenogenesis, in which the egg is activated to growth without fertilisation, but cannot lead to a live birth. Such tumours can be benign or malignant. In their non-malignant form, they are known as mature teratomas and are characterised by limited growth and disorganised but highly differentiated tissue:

The result is a bizarre growth known as a teratoma: a disorganised mass of cells containing many varieties of differentiated tissue—skin, bone, glandular epithelium, and so on—mixed with undifferentiated stem cells that continue to divide and generate yet more of these differentiated tissues.20

The case referred to here is an ovarian parthenogenetic tumour. More rarely, teratomas can be found at the base of the spine in newborn babies. Similar tumours can originate in adult males, too, from the germ cells in the testis.

These truly bizarre parthenogenetic growths have been found to contain sebum, clumps of matted hair, protruding lumps of bone, cartilage, bronchial and gastro-intestinal epithelium and even teeth (a recently reported specimen was found to contain eight well formed teeth set in a jawlike bone structure).21

In their malignant form, on the other hand, these tumours are known as immature teratomas or teratocarcinomas and are characterised by undifferentiated cells with an unlimited capacity for growth. Although they rarely metastasise or infiltrate surrounding tissue, these tumours grow very rapidly and will continue to grow until they kill their host through emaciation. Despite their differences, it is possible to derive a teratocarcinoma from a teratoma by continuously transplanting samples of the tumour cells from one host to another. Teratocarcinomas can be established as permanent cell lines (embryonal carcinoma [EC] cell or ECC lines) and induced to proliferate indefinitely, without differentiating. When exposed to certain agents, however, they can be provoked into differentiation and, like the teratoma, produce a disorganised conglomerate of apparently normal specialised cell types.

Leroy Steven’s decisive contribution to the field of ES cell research was to show that teratomas were intrinsically related to processes of early embryonic growth. He was thus able to demonstrate that these tumours not only occur spontaneously in the germ cell, but can also be induced in the adult body by grafting the inner cell mass of early embryos into the testes of adult mice. These experimentally produced growths behaved just like spontaneous teratomas, differentiating into a disorganised mass of multiple tissues. Such results suggested that teratomas could be understood as an effect of the deregulation of the normal limits to growth rather than an inherent mutation—a morphological rather than a genetic disorder. Commenting on this experiment, B Alberts et al comment that “separating the cells from their normal companions deprives them of cues that would ordinarily limit their proliferation and promote their progressive differentiation.” Conversely, the authors note that the deregulated growth of both ES cells and EC cells appears to be reversible if the cells are resituated in a normal developmental environment. (Alberts B, et al,20 pp 897–8).

It is to this experiment that we owe the first identification of ES cells. Having transplanted the inner cell mass into adult tissue, Stevens noted that “some of the early embryo cells gave rise to teratomas”; the “induced growths looked and acted like spontaneous teratomas, yielding embryoid bodies when transplanted into mouse bellies and displaying an impressive range of tissue types”. These cells could also be induced to grow as permanent, undifferentiated cell lines, just like the teratocarcinoma. Stevens named these cells “pluripotent embryonic stem cells” (Lewis R,17 p 2). ES stem cells, in other words, were discovered as experimental counterparts of the teratocarcinoma—monstrosities, according to the language of nineteenth century biology (Shostak S,18 p 182).

Indeed when ES cells were first discovered, their sole interest was thought to lie in the field of research into cancer and cell differentiation.

The idea of exploring their therapeutic possibilities emerged much later, following successful experiments using adult stem cells for bone marrow transplants (Shostak S,18 pp 181–2). It was only then that the properties of the ES cell were “rediscovered” as being essentially benign and thereby distinguishable from those of EC stem cells, although the precise nature of this difference is yet to be defined with any certainty, as I will later show.

Two events mark the emergence of the field of embryonic stem cell research as we now understand it: the isolation of the first stable, long term cultures of embryonic stem cells from mouse embryos in 1981, and from human embryos in 1998.22–24 It was these “normal” embryo derived cells that became commonly known as embryonic stem cells.

Returning to Leroy Steven’s early work, I am struck by the fact that stem cell research, with its historical connection to studies on teratomas, appears to have followed up precisely the line of inquiry suggested by Isidore Geoffroy Saint-Hilaire. In his passionate reflections on the parasitic monstrosity, Isidore predicted that the study of teratomas would provide invaluable insights into the processes of material organisation and illuminate the nexus between embryological and monstrous growth:

I suspect that one day physiologists will pursue the study of amorphous monsters with an ardour equal to the indifference that almost all have shown up until recently, and that science will here discover perhaps unhoped for illumination on the mysteries of the first moments of formation of the animal. But these advances are still far from us: laborious research, abetted by favourable circumstances, is necessary in order to carry them out. In the present state of science, we are lucky if we possess a few precise descriptions, a few exact figures of parasitic monsters, and their scientific interest has even been so little felt that observers have almost always neglected to preserve those that chance has offered them (Geoffroy Saint-Hilaire I,2 pp 538–9).

Isidore Saint-Hilaire recognised the extreme importance of the “parasitic monster” for any future investigations into embryology, but was powerless to reproduce them experimentally in his still largely tentative forays into teratogeny. Dareste, whose systematic teratogenic experiments were more successful, dismissed the “parasitic monster” as an unverifiable, and perhaps non-existent, conceptual artefact. (Dareste C,5 p 230). When Leroy Stevens returned to the teratoma, according it all the importance that Geoffroy Saint-Hilaire had foreseen, he not only studied its spontaneous occurrence in mice but also developed a subtle experimental protocol for provoking it into growth. In his ambition to lead organisation along anomalous paths of development, Geoffroy Saint-Hilaire was vindicated—the applied science of teratogeny had succeeded in reproducing that extreme case of the anomalous which Geoffroy Saint-Hilaire classified as a “parasitic monster”.

Recent work on teratomas has, however, discovered aspects of the parasitic monstrosity which remained obscure to Geoffroy Saint-Hilaire: its relationship to parthenogenesis (explicitly denied by Geoffroy Saint-Hilaire) and to cancer (implicit in its renaming as a teratoma or monster tumour). Steven’s work on teratomas combines Geoffroy Saint-Hilaire’s intuitive insight into the connection between “parasitic monsters” and embryological development with later experiments on induced parthenogenetic growth. Most famous among these are Jacques Loeb’s successful attempts, in 1900, to activate the parthenogenetic growth of unfertilised sea urchin and frog eggs by pricking them with a needle or altering the concentration of salt in sea water.

The nexus between these three aspects of stem cell research—parthenogenesis, cancer, and embryology—continues to inform recent developments in the field. A number of different techniques have been employed in the experimental production of ES cells. The first stable, long term cultures of embryonic stem cells were derived from mouse and human embryonic tissue in 1981 and 1998 respectively. Another line of research has sought to produce immune compatible ES cells by creating cloned embryos from the combination of an enucleated egg and an adult somatic cell of the prospective patient (a technique known as somatic cell nuclear transfer). More recently, however, research has returned to the connection between stem cells and parthenogenesis. In 2002, scientists based in the US provoked monkey egg cells into dividing without fertilisation, using chemical signals similar to the ones involved in fertilisation by sperm. Although experimental parthenogenesis is routinely carried out with laboratory mice, this was the first such experiment to successively induce asexual development in a primate. In such experiments, the cells of the unfertilised egg grow up until the blastocyst stage, but are unable to develop beyond this into a fetus. These cells, known as parthenotes, are essentially genetic clones of the unfertilised egg, and yet as clones they are unable to develop into a morphological “reproduction” of their mother. When the cells of the unfertilised egg reached the blastocyst stage, scientists harvested the inner cell mass, deriving stem cells which they then provoked to differentiate into numerous cell types including brain, heart, nerve, and smooth muscle cells.25


In its ambiguous proximity to cancer, the ES cell unsettles the received scientific distinction between the normal and the pathological. Cancer, after all, is commonly defined in purely negative terms as a deregulation of the normal limits to cellular growth, differentiation and division:

Creating and maintaining tissue organisation requires strict controls on cell division, differentiation, and growth. In cancer, cells escape from these normal controls and proceed along a path of uncontrolled growth and migration that can kill the organism.26

Ignoring the normal limits to growth, most cancerous cells are characterised by excessive multiplication through continual self division and relative lack of differentiation, and when malignant, by the ability to “metastasise” or infiltrate surrounding tissues and spread to distant sites of the body. Most cancers arise from a mutation in a single cell which proceeds to reproduce itself through uncontrolled self division (in this sense they are said to have a “monoclonal” origin).

In textbook introductions, the deregulated growth of cancer is defined against a number of assumptions concerning the limits to normal cellular growth, differentiation, and division. In general terms, processes of cellular growth are conceived of as a progressive restriction of potency:

A common notion that has prevailed in developmental biology for many years is one of cell differentiation during embryogenesis proceeding through a series of successive binary decisions by which cells adopt alternative phenotypes. Thus embryogenesis is commonly seen in terms of cells following branching pathways of differentiation. The branching pathways are seen as representing successive commitment of cells progressively to restricted options of eventual cell fate (Andrews P,27 p 8).

Development, it is assumed, is an irreversible process leading from the undifferentiated and totipotent cells of the early embryo (capable of giving rise to all the germ and somatic cells of an organism), through a progressive and irreversible restriction of cellular fate, committing cells to mutually exclusive paths of differentiation. In the course of development, the cells of some tissues undergo terminal differentiation, culminating in cell death and the final cessation of cell division. In other tissues, old cells are continually lost and replaced by new ones, through the division of undifferentiated, “progenitor” or adult stem cells, cells which are capable both of continually renewing themselves and differentiating into specific daughter cells. Haematopoietic stem cells, precursor cells in the liver, and neural stem cells—for example, continue to regenerate specific cell tissue throughout life. In normal growth, it is assumed, the relationship between cellular division and differentiation is maintained within strict regulative limits, preventing either one from predominating over the other. Whereas cell division tends towards the extreme of limitless, but undifferentiated growth, cell differentiation is associated with a progressive restriction of function, leading to terminal differentiation and a complete cessation of cell division. Normal growth itself is envisaged as a precarious balancing act between these two tendencies. As one recent overview puts it, adult stem cells tread a fine line between death (terminal cell differentiation) and immortality (unlimited, undifferentiated division).28

According to recent definitions, it is this “fine line” between differentiation and (undifferentiated) division which is disturbed in cancer. In most forms of cancer, the cell is afflicted with a persistent and pathological non-differentiation. There are no limits to its proliferation, it would seem, because it refuses to commit itself to a determined, irreversible path of differentiation. Hence most cancers arise from (stem) cells undergoing continuous division. The most frequent forms of cancer are those of the epithelia (epidermis and lining of the gut), tissues that are constantly being renewed by division and differentiation of stem cells. “In normal epithelia, cells generated by stem cells continue to divide for a little time until they undergo differentiation, when they stop dividing. By contrast, cancerous epithelial cells continue to divide, although not necessarily more rapidly, and usually fail to differentiate” (Wolpert, et al,26 p 429). Leukaemias, cancers of the white blood cells, are likewise characterised by the failure of resident stem cells to differentiate, while dividing. “All blood cells are continually renewed from a pluripotent stem cell in the bone marrow, by a process in which steps in differentiation are interspersed with phases of cell proliferation. The pathway eventually culminates in terminal cell differentiation and a complete cessation of cell division. Several types of leukaemia are caused by cells continuing to proliferate instead of differentiating” (Wolpert, et al,26 p 429).

The equation between undifferentiated growth, disorganised differentiation and the pathological continues to inform the most recent textbook introductions to cancer. But are these properties inherently pathological or malignant? The isolation and identification of ES cells has raised some provocative questions in relation to the concept of the pathological. Early studies defined teratocarcinomas derived from teratomas as malignant growths and set out their properties as follows:

The most important characteristics of embryonal carcinoma cells in teratocarcinomas are their immaturity, pluripotentiality, and capacity to proliferate in the undifferentiated form, at the same time to give rise to somatic tissues.29

It is in almost identical terms that recent textbooks define the properties of the ES cell derived from the isolated cells of an early embryo:

human embryonic stem (ES) cells—that is, cells obtained from the inner cell mass (ICM) of embryos at the blastocyst stage and cultured in vitro. Under suitable conditions, human ES cells can divide indefinitely and give rise to a wide range of differentiated cells.30

According to this definition, ES cells are characterised by a capacity for indefinite self division (potential immortalisation) which they retain even when they can be provoked into generating differentiated cells—a capacity, in other words, for excessive multiplication which might otherwise be associated with the pathological. Certainly nineteenth century theories of biological equilibrium would have classified the ES cell as a form of monstrous growth; and in the early history of twentieth century stem cell research, ES cells were equated with the immortal and therefore pathological cell lines of the teratocarcinomas. On the conceptual confusion between ES and EC cells, the specialist Peter Andrews writes:

The recognition that EC cells are the malignant counterparts of embryonic ICM cells eventually resulted in the experiments of Evans & Kaufman (1981) and Martin (1981), who showed that it is possible to derive permanent lines of cells directly from mouse blastocysts, which closely resemble the EC cells derived from teratomas. They termed these cells “embryonal stem” (ES) cells. The normal cells to which these lines are thought to be equivalent, namely the cells of the late ICM [inner cell mass], do not normally persist for any great length of time. The apparent ability of ES cells to grow indefinitely and exhibit an immortal characteristic—that is, to present classical “stem cell features”, seems to be a consequence of their removal from the embryo and maintenance in tissue culture.27

So should we define ES cells as normal or pathological, benign or malignant?

In the words of one recent textbook, ES cell lines derived from an early embryo “are almost indistinguishable from teratocarcinoma derived cell lines” produced from teratomas (Alberts B, et al,20 p 896). (There is, however, an obvious genetic difference between cells derived from a teratoma and ES cells isolated from an early embryo, since the teratoma is “conceived” parthogenetically. This difference is annulled in more recent directions in stem cell research which are attempting to produce ES cells for therapeutic purposes by provoking parthenogenesis. See below.) In culture, both are capable of unlimited self division and under certain conditions, “pluripotent” differentiation. If retransplanted into an embryo, on the other hand, both lose their power of unlimited self division and participate unobtrusively in the normal process of embryogenesis.

In light of these confusing exchanges between normal and cancerous cells, what remains as a definition of ES cells is simply their propensity to grow outside the limits of regulated growth and differentiation, as defined by cell theory since the nineteenth century. The isolation of ES cells has called into question established scientific notions of cellular fate, potency, and determination. In the normal course of human embryogenesis, the totipotency of early embryonic cells is already restricted after the eight cell stage. When isolated from their habitual conditions of growth, however, the same cells acquire a potency which is no longer subject to the rule of progressive, restrictive determination and therefore retain the capacity for unlimited division and “pluripotent” differentiation. These experiments suggest that the potency of a cell (limited or unlimited) is a function of the collective regulatory networks in which it participates rather than an innate property. The capacity for unlimited division which characterises ES cells is not, it would seem, inherently pathological. Rather, as one astute early commentator pointed out, the ES cell forces us to interrogate our very notions of the normal and the pathological, the benign, and the malignant:

Differentiation in teratomas is comparable to the normal process in the intact embryo. This all has led to the question: are the embryonal carcinoma cells really malignant or is a teratocarcinoma a malignant tumour only because it contains undifferentiated, otherwise normal embryonic cells? Finally, can one draw the demarcation line between the normal embryonic cells and the stem cells of teratocarcinomas?

The answer to this question is not possible, because the commonly used concepts and criteria do not apply to this tumour model.

Teratocarcinomas are malignant not because of dedifferentiation of somatic cells but because the differentiation of their stem cells does not occur and they retain the undifferentiated form. This by itself of course, does not imply that these undifferentiated cells are “malignant” cells. Malignancy is a most useful clinical designation, but in experimental tumour research, the differences between normal and malignant cells are not always so evident that a sharp distinction should be always warranted.

Several biological methods were proposed to differentiate the malignant from benign cells. Some of them were applied to the study of teratocarcinoma, but the conclusions drawn from such experiments are not unequivocal (Damjanov I, et al,29 p 115).

In ES cells, biologists seem to have discovered cells which are equally available to normal and pathological possibilities of growth. Depending on the context of their growth, stem cells can be associated with the earliest stages of embryogenesis, the limited regenerative capacities of adult tissues, and the pathological properties of cancer. (The behavioural proximity between ES cells and teratocarcinomas remains a subject of debate in stem cell research. Recent studies have established a molecular link between cancer cells and ES cells, even when the latter have been derived from the “normal” early embryo. The very powers of regeneration which stem cell research is seeking to harness bring with them an as yet undefined risk of cancer.) Their capacity for unlimited, undifferentiated growth and disorganised differentiation—–up until recently associated exclusively with the pathological or the monstrous, to use the language of nineteenth century biology—–is here being rediscovered as a kind of protolife, the source and condition of all growth, whether “normal” or “pathological,” benign or malignant.


In a recent work, the philosopher and historian of science, Rémy Lestienne remarks that in the last instance we tend to define life in relation to death. Our most common, intuitive conceptions of biological life assume that there is no life without mortality, that ultimate limit to growth. And yet this assumption is far from being scientifically established:

It is not absolutely certain that death is the inevitable outcome of life. Some simple beings, such as sea anemones, do not seem to grow old and enjoy a longevity apparently limited only by accident. The record for observed agelessness belongs to the colony of sea anemones harvested in 1862 by Anne Nelson for the aquarium of the University of Edinburgh and preserved under constant surveillance, without change or apparent aging, for more than eighty years. The sea anemones were abandoned and accidentally perished during World War II.31

In what sense is biological life defined by its relation to death? It is no accident, I would suggest, that this question is returning to the fore in the context of recent developments in the life sciences. Late nineteenth century biology established that unicellular life forms are immortal through self division. The life of bacteria and unicellular organisms can only be terminated from the outside, when they are devoured or demolished by parasites. Multicellular life forms, on the other hand, are doomed to senescence—a process of aging which is integral to the very organisation of their cells. And yet there are exceptions to the rule. The multicellular freshwater polyp, Hydra, is capable of indefinite self regeneration through a process of cloning. The ES cells and cancer cells of metazoans are capable of seemingly unlimited division in culture.

Canguilhem, writing on normative nineteenth century conceptions of life, such as those developed by Bichat, Bernard, and Comte, tells us that the properly organic notion of life is fundamentally associated with limits—limits to morphological form, the relative limit of metabolic equilibrium which distinguishes health from illness, sexual differentiation as a condition of sexual reproduction, and as a consequence, that ultimate limit to growth, individual mortality (Canguilhem G,8 p 172).

In the atmosphere of feverish and uncertain experimentation of the late eighteenth century, these limits were not yet so indelibly established. In particular, the epigenetists (natural scientists in the Aristotelian tradition) were fascinated with modes of life which would later be considered marginal—nematodes that can survive for years in a state of suspended animation, without metabolism, before returning to life; the immortal Hydra, and aphids which in certain seasons reproduce through parthenogenesis. Not surprisingly, the epigenetists were responsible for the scientific treatises on monstrosity which would later be developed by the nineteenth century teratologists, including Étienne and Isidore Geoffroy Saint-Hilaire.

In the parasitic monstrosities, Isidore Geoffroy Saint-Hilaire discovered an obscure zone where life could no longer be defined in its essential relation to limits, a “latent” life that continued to grow while remaining perpetually embryonic, a life that would never be born but appeared capable in principle of outsurviving its mother. The morphological form of these monstrosities was “indeterminable”. In cases where they seemed capable of indefinite growth (here Geoffroy Saint-Hilaire appears to have been referring to malignant teratomas), their death could only come as it were “from the outside”, as an accident.

More recent studies on teratomas and teratocarcinomas provide a more exact formulation of Geoffroy Saint-Hilaire’s intuitive insights into the nature of anomalous growth. Teratogenesis indeed calls into question the “rules” of cellular differentiation and growth which twentieth century biology inherited from nineteenth century theories of the cell. The growth of the teratoma is not “organic”, in the normative sense of the term—the differentiation of functions and organs is not orchestrated by an implicit form, a teleological end which would constrain the multiplication of differences within precise limits and rules of non-contradiction. The teratocarcinoma remains undifferentiated but ignores the temporal limit to generation. In culture, it appears capable of unlimited self division. Like cancer, it is immortal (in the sense that its death does not come from within, but can only intrude from the outside, as an accident). Moreover, teratomas and teratocarcinomas pose a challenge to the ultimate principle of non-contradiction underlying all normative conceptions of organic life in the nineteenth century—sexual difference as a condition of organic reproduction. As Geoffroy Saint-Hilaire insisted, the teratoma is indeed the product of a genuine conception. But this is a birth without fertilisation, conception as parthenogenesis—the multiplication of life from one reproductive cell. The growth of the teratoma enacts a kind of autogestation, the reproduction of the self as a clone. But while the teratoma is a genetic clone of the egg cell, its disorganised growth in no way respects the rules of morphological self reproduction. Like the monoclonal cancer which proceeds to reproduce the somatic cell through a process of delirious and fatal self multiplication, the teratoma threatens to engulf the body in its own embryogenesis.

Teratomas, being cancers of the germ cell (the egg or the sperm), mimic “the beginning of life” with apparently authentic authority. Egg cell division, after all, is the original story of “life”. The Adam and Eve of contemporary biological discourse, the egg and the sperm are the specialised cells which need each other to be complete. But the teratoma goes it alone. Too impatient to wait for the correct pairing of opposites (the natural union of the two sexes), cell division in this case begins not the process of creation but that of potential destruction. The unfertilised egg divides and tries to compensate for the lack of the masculine counterpart. But such parthenogenetic assumptions can only lead to trouble. This deviant fetus threatens the mother’s body by destroying its internal “social” order (Stacey J,23 pp 91–2).

What is exceptional about recent developments in stem cell research is the fact that such monstrous possibilities are being exploited as a source of regenerative tissue. It is envisaged that the enormous potential of stem cells to proliferate and generate differentiated cell types might be harnessed to produce specific kinds of tissue on demand. The very traits that define teratogenesis as pathological—disorganised growth and differentiation in the case of the teratoma, the unlimited proliferation of the teratocarcinoma—are here rediscovered as benign, even regenerative, possibilities. Here, I think, lies a fundamental shift in our understanding of health and medicine. For the science of regenerative medicine, health can no longer be identified with the equilibrium of the self regulating organism, but comes to be associated with the body’s capacity for cumulative, proliferative growth in far from equilibrium conditions. Health has become excessive rather than homeostatic. At the same time, stem cell research calls into question the difference between the regeneration and reproduction of the body, between regenerative and reproductive medicine. The process of tissue regeneration is reconceived as an act of permanent autogestation, an embryogenesis which can be re-enacted throughout life.

In the process, the deregulated growth of the monstrosity, that ultimate countervalue to normative theories of organic life, comes to represent the most extreme potentiality of life itself.


I would like to thank the reviewers of this article for their comments and suggestions and for pushing me to delve deeper into the complex history of stem cell research. I would also like to thank Professor Peter W Andrews from the Department of Biomedical Science, University of Sheffield, for providing me with detailed information on the connection between teratoma research and stem cells and Dr Wendy Chee, pathologist at Prince Alfred Hospital, Sydney, for clarification on cancer and teratomas. Lastly, I would like to acknowledge the inspiration provided by Jackie Stacey’s work, Teratologies: a Cultural Study of Cancer.

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