A precious, mouldering pleasure ‘tis
To meet an antique book…
Fortunio Liceti (1577-1657) was an Italian physician and scientist who spent most of his long career as a professor of medicine at the University of Padua. He was a friend of Galileo and the author a veritable flotilla of scholarly books, most of which fall within the fields of medicine and natural philosophy. His special interests included the topics of generation, development and teratology.
Perhaps his most famous production is De monstrorum caussis, natura et differentiis (On monsters: Their origins, nature and variety), a remarkable tome that attempted to assemble all reports of abnormal human development. The book was originally published in Padua in 1616. Later editions were issued, again in Padua (1634), in Amsterdam (1665), and in Padua (1668), yet again.
Many of the cases that Liceti described represent well-known anomalies that are generally recognized as really occurring. In particular, he lists a wide variety of human conjoined twins, which of course, actually do occur, not only in humans, but also in a wide variety of other types of animals. A famous modern example is the case of Abigail and Brittany Hensel (see video right), and Liceti lists cases quite similar to the Hensel twins. Conjoined triplets, though far rarer, also occur (example). Liceti cites a case of this in a sheep (right). Human conjoined triplets, too, are known. He also pictures individuals with extra appendages and digits, a fairly common, well-known type of abnormality.
But writing in the 17th century, Liceti also included reports that most biologists today would consider unreliable or even ridiculous. There was not then the emphasis that scientists now place on reporting and considering only what fits accepted notions of the possible. Scientific dogma now asserts that certain kinds of creatures do not exist. And if anyone now goes about suggesting that such things, denied by science, do — or even might — exist, then many people not only discount such claims out of hand, but may even assess the bearer of such tidings as mad.
But Liceti, instead of limiting himself by theories and beliefs, seems to have simply included in his compendium whatever scholars before him had reported, whatever strange abnormalities they may have described, however old the reports, even ancient classical authorities. The result was a mixture of fact and fancy.
In that book (Liceti 1634, pp. 193-194), he reports an ostensible cat-human hybrid (pictured at the top of this page), which, if real, would represent an extreme rarity: a cat-human conjoined twin in which the human portion was parasitic (parasitic twins are discussed below). His account reads as follows:
A Danish case|
In his Historiarum Anatomicarum Rariorum (Centuria II, p. 241), the Danish physician Thomas Bartholin (1616-1680) states that “At Leiden in 1638 near St. Peter's Church, a woman gave birth to a child with the head of a cat, but that was otherwise normal.” Translated by E. M. McCarthy (Original Latin).
Pignoria and Sandelli, two Paduan scholars, were friends, and friends of Liceti and Galileo, as well. They both died in a plague that struck Padua in 1631. Sandelli translated several of Galileo's works into Latin at his request (J. des Sçavans, p. 136).
Though very rare, other cases of distant crosses producing conjoined "mixed" twins have been reported. In Australia, a “calf” was born at the newly founded Hawkesbury Agricultural College, Richmond, New South Wales, in 1894 that had two heads, one of them "like a bull-dog’s.” For example, the account, which appeared in the Windsor and Richmond Gazette, the local newspaper, on October 13, 1894, reads as follows:
Several other cases of alleged dog-cow hybrids are cited elsewhere on this site, but none of the other alleged births involved conjoined twins. Also, there are very old reports of hybrid conjoined twins involving two other types of distant crosses, dog-human (pictured here) and sheep-hare.
Man with a parasitic twin (a body without a head); from Schenk, Monstrorum historia memorabilis (1609)|
Two additional cases. Left: A parasitic head without a body;Right: A parasitic body without a head (from Liceti 1634, p. 99)|
The Two-headed Boy of Bengal.|
|A contemporary case of craniopagus parasiticus.|
|Hermaphroditic conjoined twins, an extremely rare condition; from Bauhin, De Hermaphroditorum, 1614.|
A parasitic twin (also known as an asymmetrical or unequal conjoined twin) is the result of the same processes that produce ordinary conjoined twins, except that one of the two twins (the autosite) develops more completely than the other (the parasite). The condition has long been recognized. For example, the illustration at right dates to the 17th century (view photos of a similar modern case >>). The parasite can be attached to various regions of the autosite’s body. For example, in 2005 a woman in Egypt gave birth to conjoined twins in which the parasite was merely a head attached to the upper left portion of the autosite’s head (see video at right below), a rare condition known as craniopagus parasiticus, an example of which is shown in the lower figure at right. An 18th century instance of the same syndrome, the Two-headed Boy of Bengal, is pictured at right.
So what, then, is the creature pictured and described by Liceti? A figment accepted by the mere credulity of a superstitious dupe? Given Liceti’s high reputation as a scholar and his position as professor at an important university, I tend to reject this interpretation, especially given that I agree with Michel de Montaigne’s observation (Essays I, 26) that “It is foolish presumption to imagine all things false that do not seem probable, which is the ordinary vice of those who fancy themselves wiser than their neighbors.”
Not considering myself wiser than the scholarly gentlemen who attested the existence of this strange creature in their own hometown of Padua (and at a time when they themselves lived there), I am left trying to imagine how, from a biological standpoint, such an organism might have come into being. Obviously, such an event can be broken down into three consecutive stages: insemination, fertilization and development. The first of these steps could potentially occur in many ways. Only a bit of imagination is needed. Once the semen was in situ (stage 2), it would find its way to the Fallopian tubes, and there a single feline spermatozoon would penetrate a single human egg. (Obviously, the producer of a spermatozoon need not be of the same kind as the owner of the egg that it penetrates. Otherwise there would be no hybrids in the world.) These two steps, then, are fairly straightforward.
|Liceti late in life|
But the course of subsequent development is another matter. In the case of identical non-conjoined twins, a single embryo at an early stage, prior to about the tenth day of development, divides into separate embryos that go on to become two separate, but genetically identical individuals. But in the case of conjoined twins, the division begins later, after the tenth day, stalls, and remains incomplete. The separated portions develop into duplicate bodily members (two heads, two bodies, etc.) and the undivided remainder becomes the non-duplicated moiety of the mature conjoined organism. Though it is somewhat surprising that development proceeds and that such partially duplicate organisms are viable, it is still fairly easy to imagine: the partially divided cell mass of the embryo grows by cell division and the separated parts of that mass map onto the duplicated parts of the mature organism, and the non-separated, onto the non-duplicated.
But what sort of mechanisms would have governed the development of Liceti’s composite creature? How could human legs grow on the hind end of a cat? From my general research into mammalian and avian hybrids, I know that in many, more ordinary crosses the resulting hybrids look like composites of their two parents. For example, they might have the legs of one parent and the head and body of the other. Thus, zebra-ass hybrids often have the striped legs of a zebra even though the rest of the body looks like that of an ass. So it seems that by some unknown mechanism, the influence of the genetic material of one parent can predominate in one portion of the body, while that of the other predominates elsewhere. Indeed, in some crosses, the genes of one parent so dominate those of the other that the hybrids are phenotypically identical to the dominant parent.
Putting these facts together one can suppose that in a hybrid conjoined twin of the sort pictured at the top of this page, the unknown mechanism just mentioned causes one of the two separated portions of the partially divided hybrid embryo to develop as human, whereas the same mechanism or switch sets the remainder of the embryo to develop as a cat.
One can imagine various mechanisms that might bring such a result about, but such suppositions can never amount to anything more than speculation in the absence of experimentation and observation.
It seems appropriate to close this article with a translation of a brief notice that appeared in the August 26, 1875 issue of the Viennese newspaper Welt Blatt (page 9, column 2):
Somehow, though, if it were I who had just given birth to a son with “a head exactly like that of a cat,” I don't think I would choose to say that we were doing “just fine.”
The following is a list of reported cat crosses. Some of these crosses are much better documented than others (as indicated by the reliability arrow). Indeed, some might seem completely impossible. But all have been reported at least once. The links below are to separate articles. Additional crosses, not listed here, are covered on the cat hybrids page.
By the same author: Handbook of Avian Hybrids of the World, Oxford University Press (2006).
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