MONSTROSITIES. , 413 



ists between many anomalies and various transitory conditions of em- 

 bryonic organization. 



It has been well remarked that the majority of the malformations due 

 to defect in the higher animals, represent, in a more or less perfect man- 

 ner, the normal conformation of the inferior classes. For instance, the 

 imperfection or absence of limbs is the natural condition of fishes and 

 some reptiles ; the heart is not present in zoophytes ; when it has but 

 one cavity in the higher mammalia, it only resembles the single heart of 

 crustaceae ; and when the auricular septum of the heart remains patent, 

 it is like the reptilean heart. All this is explained by the fact, that the 

 embryo of the domesticated animals, in arriving at its ultimate develop- 

 ment, appears to pass through all the degrees of organization which mark 

 the different types in the zoological series. And by means of the knowl- 

 edge we possess of the organization of these types, we are sometimes 

 able to say when a particular monstrosity began to deviate from the 

 normal condition, the nature of the deviation, and its cause. 



An excess of general development is less frequent than the opposite 

 condition : partial excess of an organ or region is not unfrequent ; while 

 excess of parts is far from rare, and may be noted in the vascular sys- 

 tem, in internal organs, and externally : more particularly is it remarked 

 in the extremities, when we have in some species "polydactylism," and 

 in others " hvperdactylism." It is often obseVved that an excess in 

 development in one part coincides with defective development in an- 

 other, as if the balance in formative organization must be maintained 

 throughout the body. 



With regard to double monstrosities — the result of two foetuses being 

 accidentally joined together, and fused, as it were, into each other — G. 

 Saint-Hilaire proposed a special law which he designated the law of sim- 

 ilar imion or of mutual affinity. The result of this law is the production 

 of symmetrical development in a double monster in as perfect a manner 

 as in a single and normal individual ; the two creatures which, by their 

 union, form either a partial or complete double monstrosity, are always 

 joined by the homologous faces of their bodies — side to side, front to 

 front, or back to back. And not only are they united by their homolo- 

 gous surfaces externally, but internally they are allied by homologous 

 organs : each part or viscus of one corresponding to a similar part or 

 viscus of the other ; so that each vessel, nerve, or muscle on the plane 

 of union of one, notwithstanding the apparent complexity, is joined to 

 the corresponding vessel, nerve, or muscle of the other : just as the two 

 moieties of a single and central organ, originally distinct and lateral, be- 

 come naturally fused together at a certain period, and in obedience to 

 the laws controlling their formation and development. A double mon- 

 ster IS, therefore, only a being composed of four more or less complete 

 moieties instead of two, as in the single individual. 



With regard to more complex monstrosities, we find that, instead of 

 two moieties, as in the normal condition of an individual, or the four 

 moieties as in the double monstrosity, we may have six, eight, or even 

 more ; but yet the law of similar union prevails, and the moieties com- 

 bine m twos. Therefore it is that a triple monstrosity is only a double 

 monstrosity doubled, and a quadruple one a triple monstrosity doubled 

 also — all the phenomena of the compound monstrosity being accounted 

 for on the same general principle. 



The formation of double monstrosities has given rise to some digcus- 



1 



