414 FCETAL DYSTOKIA. 



half of each. The separation of the two halves may occur at one 

 extremity or at both, and it may extend to any depth. According to 

 these differences, we should have the various forms of double monster — 

 from such creatures as the Siamese twins to cases of a small super- 

 numerary leg. There may even be a further stage of this process. One 

 of the separated halves may present a similar exaggeration of bilateral 

 symmetry, if it again separate into two halves like the original germ. 



Thus may be explained monsters with three heads or three tails. 



Some objections might be raised to this theory, but this is not the 

 place to enter upon their discussion. "We may, however, point out 

 that it will scarcely apply to included monstrosities, in which we have 

 one creature, more or less perfectly developed, contained within 

 another. We can scarcely doubt of the -existence of two ova, the 

 included one being the oldest, and that this inclusion has probably been 

 effected at a very early period of germ development. 



To return, however, to the long-accepted theory. If wx descend 

 from the complex phenomena of double monsters to single ones, and 

 from these to simple anomalies, we find again that every anomalous 

 union between organs takes place by homologous parts. What have 

 been designated " Symelian " monstrosities are characterized by the 

 fusion of their more or less atrophied abdominal limbs ; in the " Cyclo- 

 cephalian " monsters the eyes are more or less fused into one organ of 

 vision ; while with the " Otocephalians " tbe ears themselves are 

 joined, and often intimately confounded. The union of the kidneys, 

 testicles, cerebral hemispheres, and other double organs, is often 

 observed in creatures otherwise normal in conformation ; and all these 

 anomalies occur under the reign of the same law — that of " similar 

 union " — which for organs, as for entire individuals, operates on homo- 

 logous parts. 



With regard to the remote or proximate causes which lead to the 

 production of monstrosities, it is very probable that the most pi'ominent 

 are irregularity or inequality in the nutrition of the foetus, physical 

 injury, undue pressure, alterations in the membranes, or diseased 

 conditions of the young creature. G. Saint-Hilaire and Valentine, by 

 disturbing the development of the embryo of the fowl during the early 

 stage of incubation of eggs — through shaking, jarring, and pressing 

 them, perforating the shell, or covering it with wax — could almost 

 create monstrosities at will. And an accident during gestation — a 

 blow, a fall, a displacement of the uterus — will produce the same 

 results in animals. Lafosse observes that it is perhaps because of 

 the pressure to which the foetus of Euminants is exposed, owing to 

 the accumulation and fermentation of food in the rumen, that must 

 be attributed the greater frequency of anomalies in the species of this 

 order than in the other domesticated animals. The quantity and 

 quality of the food, as well as the work to which the mother is sub- 

 jected, have an undoubted influence on the nutrition of the embryo. 



A circumstance which appears to have some influence in the pro- 

 duction of anomalies in animals, is the great disparity in size between 

 the male and female. Lafosse endeavours to prove this by showing 

 that the frequency of certain vices of conformation — such as hypo- 

 spadias, umbilical hernia, want of proportion between the jaws, etc. — 

 is most notable in the mule. 



We are also convinced that excessive consanguinity (breeding "in 

 and in ") likewise leads to the frequent production of monstrosities ; 

 we have witnessed some startling instances in the Cow and Pig. 



