DUPLICITY. 19 



94. A female Human foetus with posterior dichotomy (Schizo- 



rhachis) combined with anterior dichotomy, producing 

 considerable doubling of the face. There are four eyes, 

 but the inner ones are contained in a single orbit. The 

 axes diverge, both in front and behind, from a point in the 

 basisphenoid bone. Hunterian. 



Subclass II. Homologous union. 

 A. Prozygosis*. 



Syn. Somatodidymus, Gurlt. 



Monstres Syncephaliens, Geoff. 

 Synkephalus symmetros, Forster. 

 Janus-Bildung. 



In Prozygosis there are two perfectly distinct axes united at 

 their anterior extremities, so that at an early stage there must 

 have been two distinct embryos. The foetuses arising from such 

 embryos are united by the visceral arches and laminae above the 

 umbilicus. The right side of one axis unites with the left side 

 of the opposite one. 



95. Female Human twins, about the seventh month of gestation, 



united by prozygosis. The faces are opposite to each other, 

 and at right angles to the normal position; they are 

 much flattened, the eyes are closely approximated, and 

 the ears are very low down. The two embryos were pro- 

 bably distinct at first, and became united by the fusion of 

 the anterior extremities of the investing mass of each with 

 that of the other, so that the trabeculse became united in 

 the same manner as the other facial arches are joined, 

 the right arch of one embryo being fused with the left 

 arch of the other. 



The following history is recorded: "Labour lasted 

 forty-eight hours, delivery followed without instruments. 

 The mother, a negress, had convulsions. The foetuses 

 lived five minutes, a very unusual occurrence in such 

 cases. There was one funis and one placenta." 



Presented by T. Sharp, M.D., 1820. 



96. A similar twin-birth about the sixth month of gestation, 



* Upo before, vyow to unite. 



c 2 



