DUPLICITY. 29 



the glenoid cavity is articulated with the clavicles. The 

 cartilage already mentioned, situated between the clavicles 

 and glenoid cavity, is the only rudiment representing 

 the anterior median limbs. 



121. The viscera of the same; these are double, but those of 



the right foetus are considerably smaller than those of 

 the left ; the latter are reversed. The hearts were situ- 

 ated in distinct pericardia. The heart of the left is 

 three times the size of that of the right foetus. The latter 

 gives off a small aorta, which joins the descending aorta 

 of the left foetus just below its arch. The livers are in- 

 timately united ; the oesophagi, stomachs, and duodena are 

 distinct as far as the orifice of the bile-duct, where the 

 intestines unite in a sacculate dilatation ; below this point 

 the intestine is single but reversed, the caecum being on 

 the left side. 



d. Ischiopagus, Forster. 



Syn. Pygodidymus, Gurlt. 

 Pygopagus, Geoff. 



In Ischiopagus the twins are united by the lower extremity 

 of the axis only, and are placed back to back, so that the visceral 

 cavities are distinct. Judith and Helena, " The Hungarian Sis- 

 ters " (Phil. Trans, vol. 50, p. 31 1) , and Millie-Christine, the "Two- 

 Headed Nightingale," exhibited in London in 1871 (Lancet, 

 1871, i. p. 725), are examples. No specimen occurs in the 

 Museum. 



122. A wooden model representing two ischiopagous infants. 



The anus is represented as single, and the vaginae are united at 

 their posterior commissures, the usual disposition of these parts 

 in such malformations. 



Subclass III. Homologous union with dichotomy. 



The so-called triplex human foetus described in the ' Atti delP 

 Accadem. Gioen. 5 t. viii. p. 203, is undoubtedly an example of 

 pleuropagus combined with anterior dichotomy of one axis. 

 Several cases are recorded by Gurlt as having occurred in 

 animals. 



