38 



TRIPLE MONSTROSITY— CLASSIFICATION 



CLASSIFICATION IN GERMINAL TRIPLICITY. 



Three embryos 

 from one ovum. 



II 



All the bodies separate. 

 (Trisomi dieriti of 

 Taruffi, 247 III. p. 458) 



— The two united bodies 

 showing axial union. 



A Only two of the 



The bodies not 



all separate. 



(Trisomi sineriti of 

 Taruffi, III. p. 464) 



B 



bodies united. 



-The two united bodies 

 not showing axial union. 



1 — All three bodies showing axial 

 union. 



— Only two of the bodies showing 

 axial union. 



All three bodies 



united. 



-Axial union not present. 



The divisions A. 1, B. 1, and B. 2 may be further subdivided according as the union of the 

 bodies is anterior or posterior (anadidymus and katadidymus). 



A single condition of the neural axis and the axial skeleton, at least for some part of 

 their length, should be taken as their criterion of axial union. 



Notes to the Classification Table. Under I. will be included the cases of identical triplets 

 already referred to. These are probably much less rare ( l 2/+7 III. p. 460, 19, 20) in the human 

 subject than are cases of triple monstrosity. Instances of quadruple, and even of quintuple, 

 pregnancies with single chorion and placenta, and presumably of unioval origin, have also been 

 recorded (&£7 III. p. 459). 



The remarkable observation by Assheton (J. Anat. Physiol. London, 32 362) of two germinal 

 areas on a single blastocyst of the sheep, threw very striking light on the probable mode of 

 origin of identical plural embryos. Still more remarkable is the recent work of Fernandez 1 on the 

 embryology of the Edentate Tatusia hybrida Desm. Confirming and greatly extending previous 

 observations by v. Kblliker, Milne Edwards and v. Jhering, this author finds that normally in 

 Tatusia all the eight or nine foetuses in a pregnancy arise from a single ovum, are unisexual, and are 

 enclosed within the same chorionic sac. 



In the lower vertebrates, the mode of development does not, in the end, allow so complete 

 a separation of the embryonic bodies as is possible in the mammals. Taruffi, however, points 

 out with justice that, in the chick, such examples as the second quoted from Dareste, and that described 

 by Moriggia, are similar in their essentials to his mammalian trisomi. So also is the triple salmon 

 of Klaussner, according to the description stating that the three embryonic bodies were quite 

 separate except for their attachment to the common yolk-sac. 



A. 1. Examples are the fourth of the chick embryos noted above as described by Dareste 

 and that described by Koch. 



A. 2. Had it survived, the first of the chick specimens from Dareste would have come to 



1 Beitrage zur Embryologie der Gurtelthiere, I. Morph. Jahrb. Leipzig, 39 Heft 2. 



