MOXSTJiOSJTIh'S. 



409 



the last in havinf^ only one head, but a double body, the separation of 

 the two usually takinj,' place below the umbilicus (Fi^'. 117). 



The Si/soniiaii monstrosities (Fij;. US) have two heads on apparently 

 a single body, though a closer investigation will prove tliat the unicity 

 is merely superficial, and that at least some parts are double. Gurlt 

 describes a full-grown Sysomian lamb he examined, and which had, 

 apparently, a single body and only four feet, but two necks, two heads, 

 and two tails, and the skin normally covered with wool. The trunk, 

 though somewhat small, gave no indication of its duplicity. It had, 

 nevertheless, two vertebral columns, the inner ribs attached to each 

 being shortened and fused together, while the external ones were at- 

 tached in the usual way to the single sternum. The viscera were 

 generally double, though they were confounded at certain points. A 

 single heart suthced for two pair of lungs, one pair of which, however, 

 were onlv rudimentarv. The two livers were combined into one, and 



Fig. 117. 



MO.NOCErH.\LIAN- MoX- 



.sTROsiTT: Corvw-Mf- 

 lo'lidymi (Gcrlt). 



Fig. 118. 



Syhcmian Mon.strohity : Dicephalus 

 bicollis (UURLT). 



in some parts the intestines merged into a single tube, again to become 

 double, and finally to terminate in one rectum. 



The Monosomian monstrosities have, in reality, only a single body, 

 the duplicity generally commencing towards the neck, in the cervical 

 region, not un frequently at the atlas, and sometimes as far as the facial 

 region ^Fig. 119). 



Among the double parasitic monstrosities, we may mention Saint- 

 Hilaire's Hcterotn plans, in which the smallest of the foetuses is attached 

 to the anterior part of the body of the other, at or near the umbilicus ; 

 the Hctcralians, in which the parasitic foetus is very incomplete, and 

 perhaps reduced to a single region — as a head without a body — attached 

 some distance from the umbiUcus ; the Pob/f/nathiayis, in which the 

 parasite is reduced to the mere fragments of a fcrtus — the jaws and 

 some cephalic remains adhering to the jaws of the other fcetus. All 



