TEE FCETUS. 1029 



2. Pig.— The placenta is formed by an expansion of the villous tubercles, as in Solipeds. 

 The chorion is not entirely covered by these tubercles, but here and there it shows bright little 

 patches, where its tissue is merely covered by an epithelial layer ; it is also glabrous at those 

 points wliere it is in cont:ict with the chorion of neighbouring foetuses. 



The chorion has not a body and two coruua, but is merely an elongated sac, the two 

 extremities of which are in relation with the adjacent foetuses. The inner face corresponds, 

 as in Ruminants, with the amnion and allantois. The latter is the same as in the Cow, tliough 

 it is very much shorter ; the inner covering of this membrane contains the glycogenic matter, 

 but that of the amnion has none. 



The umbilical vesicle, amnion, and cord, are also the same as in Ruminants. 



3. Carnivora.— Tlie placenta is a thick gir<lle, surrounding the middle portion of the 

 chorion. It has a Uvid colour in its middle, green on its borders. When the green-coloured 

 matter is isolated, and treated with alcohol and chloroform, then submitted to certain reagents, 

 it appears to be identical with the colouring matter of the bile, and derived, as that is, from 

 the haemoglobin of tlie blood. 



The allantois is disposed, in principle, as in Solipeds. 



The chorion is quite like that of the Pig with regard to form, but it is diflferent with regard 



Fig. 565. 



SEMI-DIAGRAMMATIC VERTICAL SECTION OF A MATERNAL COTVLEDOX OF THE SHEEP. 



(^cr, Uterine sinus; e, epithelial lining of the sinus; V, veins, and c, flexuous arteries of the sub- 

 epithelial connective tissue. 



to structure, as it hac no chora plates v/ith mineral granules. Nothing is known as to the 

 organ which fulfils the function of these deposits. 



The umbilical vesicle— yfhidi remains VQvy developed at all periods of foetal life — resembles 

 in shape the allantois of the Pig, being a transversely elongated sac included between the 

 amnion and the inner allantoid lamina, and provided at its middle portion with a narrow 

 pedicle, which is prolonged into the umbilical cord ; its walls are extremely vascular. 



•The amnion is lined, internally, by the inner lamina of the allantois. 



The umbilical cord has, as in Solipeds, an allantoid portion; but it is extremely short, and 

 enveloped in a wide fold of the allantois. 



Results.— The comparative examination of the disposition of the placenta may furnish 

 valuable indications as to the procedure to be adopted in practising artificial delivery; as the 

 surgical manoeuvres should necessarily vary with the extent and disposition of the points of 

 union existing between the uterus and the foetal envelopes. 



With this practical object in view, we believe that it is useful to divide the ilomesticated 

 animals into two groups : those which have a simple, and those which have a multiple placenta. 

 The first group may be subdivided, according as the simple placenta is general or local. 



