VII. Defective Formation of the Extremities.
The origin of many malformations of the limbs may be referred to the early periods of embryogenesis. But for some of them this is impossible.
1. Want of all the extremities is an arrest of developement at that period, in which the limbs are not yet formed, and in which small tubercles occupy their places. Sometimes the superior extremities only are wanting, which urges the inferior extremities to acquire a sort of dexterity by which they may in some mea sure supply the place of the superior limbs.
Of all the examples which are known of it, that of Thomas Schweicker is the most morable. The inferior limbs only are rarely wanting, and the cases few in which there is but one superior or inferior extremity.
2. Want of the intermediate parts in the extremities, so that the hand is attached im mediately to the shoulder, and the foot to the hip. This may happen in one or in more extremities. Of the last, a very interesting example occurred in the person of a certain Marco Catonze, of whom I represent the ex ternal appearance and the skeleton in figs. 624, 625., referring for more details to my Tab. lxxvii.
3. Limbs too short. — All their parts exist in such case, but are too short, as if they were not full-grown. The malformation is however not limited to the extremities, but extends over the trunk and the head. The head has in all the known cases the aspect of hydrocephalus. The neck is short and broad, the trunk short and swollen, and the limbs short, broad, and thick. Scemmering and Otto ascribe this to congenital rachitis. But according to my opinion it ought to be attributed to defective developement, which is confirmed by the dissection, performed by C. Mayer, of such a monstrosity.
4. Limbs which seem to be truncated.—Some times the fore-arm and the leg terminate abruptly like stumps, and present the appear ance of cicatrices. I saw this on the four extremities of a calf, of which I have repre sented the external form and the dissection in my Tabula lxxviii. and lxxix. In many of the known cases this defective condition of the limbs seems to be the result of arrested developenient. In some others, however, it is the effect of mutilation produced by the con striction of the umbilical cord, or by pseudo membranes. Montgomery has given many examples of it in his article FETUS in this Cycloptedia. It is an interesting fact that from these stumps may grow rudiments of fingers, as Dr. Simpson showed me during the visit which I paid him at Edinburgh.
5. Diminished number of fingers and toes.— The highest degree of this malformation is the existence of but one finger or toe. Sometimes there are only the thumb and the little finger, as may be seen in a preparation in the mu seum of Ilovius at Amsterdam. The greatest transition towards the natural condition is the presence of four fingers or four toes.
6. Coalesced fingers and toes. — In other wise perfect limbs it is possible that hands and feet may be arrested at that inferior de gree of developement, in which they are not yet separated into fingers and toes. The child
is then born with fingers or toes, which seem to be coalesced ; but that is nothing more than a fallacious appearance. The malformation con sists really in absence of fission. Of this there are different degrees : a, complete absence of fingers and toes, instead of which there is a common mass ; b, connection of the fingers and toes by means of a membrane ; the adhesion limited to the posterior parts of the fingers and the toes, while their anterior parts are completely free. All this may be seen in figs. 626, 627, 628 7. To all these malformations of the limbs ought to be added the abnormal direction of the foot; but this is fully considered in the article ABNORMAL CONDITIONS OF Tl1E FOOT in this Cyclopmdia.
VIII. Viii Upon this interesting malformation, which for many years was the object of my own inves tigations, I should have much to say ; but my friend Paget has already given a succinct survey of its different forms in his learned Article NOSE, to which, therefore, I refer. I beg leave here to add to the observations which I have published in my former works upon the origin of Cyclopia, a few additional remarks on the subject. Is it an arrest of developement ? It cannot be denied that many deviations of the parts in Cyclopes may be referred to a previous natural form. For example, in one of my published cases the optic lobe and the brain formed one continu ous part, which is certainly an early natu ral condition. It is also certain that the disposition of the hemispheres of the brain in Cyclopes, which appear to be a single vesicle, accords with the vesicular state of the brain in the first period of its develope ment, and that the unprotected situation of the ganglia of the brain, of the cerebellum, and of the medulla oblongata, may be con sidered as a fcetal condition. But, as to the eyes, it is not so certain that their single ness is the result of an arrest of develope ment. E. Huschke has, however, main tained the opinion, that the eyes are formed by a single vesicle, which becomes sepa rated into two ; but from the more recent and accurate investigations of Bischoff, we must conclude that the optic lobes are from the beginning separated and double, taking their origin from the anterior cerebral vesicle, and that from an abnormal condition of this last, by which the rudiments of the eyes approach each other and fuse together, may be derived the cause of Cyclopia. If this observation is true, of which It is difficult to retain the least doubt, Cyclopil really ap pertains to the Verschmelzungs Bildungen of Meckel in an early period of developement. Perhaps it may be compared with the meta morphosis of the eyes in Daphnia, Cypris, Polyphemus, and Cyclops, in which there are originally two vesicular bulbs, which subse quently coalesce into one. But however this may be, it remains certain that the malforma tion of the cranial and facial hones in Cyclopes is the consequence of the abnormal condition of the brain and of the visual and olfactive apparatus.