288 THE DOCTRINE OF DESCENT. 
discoidal placenta, or that the accordance is based on 
consanguinity with the discoido-placental mammals. We 
have already (p.. 272) objected to the inference that all 
mammalian orders are akin, should be drawn with cer- 
tainty from the superficial accordance of the placenta, 
and we must therefore justify ourselves now, when we 
lay.a stress on. the accordance of the placenta of man 
and:apes. The orders mentioned above all possess a 
placenta of small extent and discoidal form. In the 
shape of this disc, and in the number and distribution 
of the blood-vessels in the umbilical cord by which the 
fcetal respiration and nutrition are carried on, sundry 
varieties occur. Thus in the family of the Pithecoid 
apes, the placenta falls into two discs, whereas the 
umbilical cord agrees with that of man; in the American 
apes, on the contrary, the placenta is simple and the 
blood-vessels are different. In the orang and gorilla we 
know nothing of these organs, but the chimpanzee agrees 
with man, in that it has a simple discoidal placenta 
with two conducting (arteriz umbilicales) and one re- 
conducting vessel (vena umbilicalis). 
With a general similarity of the human placenta with 
that of the discoido-placental mammals, man is specifi- 
cally nearer to one at least of the so-called Anthropoid 
apes, than this one is to the other apes. And thus the 
constitution of the placenta is certainly of great impor- 
tance in discriminating the systematic position of man. 
Enormously improbable as is the chance contemplated 
above, equally probable and solely credible is con- 
sanguinity ; and with regard to general organization, in 
any specific comparison of man with the mammalia, the 
apes must occupy the foreground. 
