The malformations occasioned by impeded developement may, for the most part, be com pared with the natural forms through which the foetus passes in its normal developement. On this is founded the ingenious idea of Meckel, previously suggested by Wolff, that most malformations are caused by arrest of developement (bildungshemmung), for which reason they must be said, according to Bischoff; to be formed through arrested de velopement (hemmungsbildungen). They, how ever, never give us a perfect representation of the form at which the foetus has been arrested in its developement, because the in creased growth and the progressive nutrition of the fcetus cannot but make an important modification therein. As the transient forms of the human fcctus are for the most part comparable to the persistent forms of the lower animals, the malformations occasioned by impeded developement often acquire a brute appearance ; and thus a reason is at the same time given why they exhibit, in dif ferent animals, the form of the lower, but not of the higher classes.
A consequence of this mode of origin is, that they never deviate so much from the normal form as would exclude them from the rank of organized beings ; and that the devia tions from the natural form are confined within definite limits, so that they always re remind us more or less of the regular form. Fixed laws of organization prevail in them, by which they exhibit a certain fitness of organization, and a tendency to render the capacity for life as great as possible, not withstanding the malformation. Peculiar vi tal relations are hereby produced adapting them for uterine life, and many are brought forth well nourished and at full time. Most, however, are unfit for life after birth, though for very different reasons.
The following remarks may serve for the elucidation of these peculiar vital accommo dations :— 1. We never see in malformed births, dis similar parts fused or united with each other, such as the intestinal tube with the aorta, the arteries with the nerves, &c. Each part, therefore, retains, to a certain degree, its own independence, according to what Fleisch mann denominates lex proprzetatis. The gullet sometimes coalesces with the larynx, and the bladder with the rectum ; but these parts are not originally dissimilar, being developed from a common mass.
2. The malformed parts are restricted to their determinate place, according to what Fleischmann denominates lex topicoruni.
3. No malformed organ loses entirely its own character, and no malformed animal loses its generic distinction. It is, therefore, justly observed by Smmmering, that nature does not deviate ad infinitum, and that even in mon strosities a distinct gradation and natural or der are observable.
An immediate consequence of this must he, that in one and the same sort of monstrosity, there are different degrees of malformation, varying from the greatest possible degree to the very least. We might thus consider the different monstrosities as so many genera, and their varieties as so many species, by, according to J. T. Meckel, a new or ganic kingdom is constituted, differing only from the others by less constancy of form. Consequently a definite type prevails in the generation of monstrosities, and they are subjected to fixed organic laws. This order
appears even —1. In the number in which they occur within a certain space of time. In 3000 births in Paris, there occurs about one monster (J. Geoffi•oy St. Hilaire). 2. In the sex. In impeded developement, the mal formed children are more frequently female, in some sorts of double monsters, male. 3.
In a definite proportion between the species of the animals, and the most frequent monstrosities in them. Cyclopes, for instance, especially with a snout,occur most frequently in swine ; double monsters in man. 4. In the constant form of monsters, even amongst the most heteroge neous animals. C'yclapia, double monsters, acrania, have in Birds precisely the same cha racters as in the Mammalia. 5. In the greater predisposition to monstrosity among some animals.
This is greater among domestic than among wild animals ; greater among the more perfect, than among the less perfect ; three-fourths of the monstrosities occur among Mammalia, one fourth among Birds (J. Geoffroy St. Hi laire). They happen seldom among Reptilia, still less frequently among Fishes, Mollusca, Articulata, and Radiata.
From these premises the consequence is easily derived, that monstrosities do not take place by chance, and therefore do not by any means deserve the so very general appellation of caprices of nature (luaus vatura). The result of this is, that they often present a quantitative antithesis, according to what Geoffroy St. Hilaire denominates loi de ba lancement. According to this law, the ex cessive developement of one part of the body is often connected with checked formation of another. To anencephalia, eyclopia, spina bda, are often joined fingers and toes in ex cessive number ; to sireno-melia superfluous yertebrm and ribs ; and frequently there occur in double monsters malformations of the head. Meckel saw, in one single instance, this an tithesis extend itself over different children of one and the same mother. A girl had on each extremity a superfluous digit, and one hand of her sister wanted four fingers, being the number of digits which her sister had in excess, reckoning the four extremities together.
I have now arrived to the classification of monstrosities ; but in order to prevent all unnecessary waste of time, I shall avoid entering into a full critical examination of the systems propounded by Licetus, Huber, Wigtel, Malacarne, Buffon,Blumenbach, Bres chet, Geoffroy St. Hilaire, Gurlt, Otto, and Bischoff. Concerning these I refer to Bis choff4, from whom Rokitansky has chiefly borrowed what he gives in his manual. Ac cording to my conviction, no suitable clas sification of monstrosities can be given, and the efforts employed to this end may be re garded as failures. I confine myself, therefore, to a simple grouping, taking embryogenesis as my basis, without presuming on any further classification, and I thus avoid a barbarous nomenclature, which, in my opinion, is at tended with no advantage. My object is simply to make the doctrine of malformations useful for physiology and for medical practice, nearly in the same manner as was done, almost