THE PLACENTA OF RUMINANTS. 



95 



Insectivora ; the Cheiroptera ; the Rodentia, to which the .lowest 

 apes present so many remarkable approximations; and the 

 Carnivora (united into one group with the Insectivora by 

 Cuvier) are all as closely connected by their placental structure 

 as they are by their general affinities. 



Fig. 44. Foetal kitten, with its membranes and placenta. The latter is seen from 

 the chorion and allantois being opened and everted. Am, amnion ; All, allan 

 PI, placenta ; Urn, umbilical vesicle. 



(From a preparation in the Museum of the Royal College of Surgeons.) 



With the Pig, on the other hand, all the Artiodactyla, alt 

 the Perissodactyla (save one, taking the group in its ordinarily 

 received sense), and all the Cetacea which have been studied, 

 agree in developing no decidua, or, in other words, in the fact 

 that no vascular maternal parts are thrown off during parturi- 

 tion. But considerable differences are observed in the details 

 of the disposition of the foetal villi, and of the parts of the 

 uterus which receive them. Thus, in the Horse, Camel, and 

 Cetacea the villi are scattered, as in the Pig, and the placenta 

 is said to be diffuse ; while in almost all true Ruminants, the 

 fostal villi are gathered into bunches, or cotyledons, which in 



