88 



COMPARATIVE PHYSIOLOGY. 



so that the removal of one involves that of more or less of the 

 others. The connection of parts is far closer than that described 



Fig. 90.— Diagram illnstrating the decidua, placenta, etc. (after LiSgeois). e, embryo; 

 i, intestme: p, pedicle of the umbilical vesicle; u, v, umbilical vesicle; a, amnion; 

 cA, chorion; v. t, vascular tufts of the chorion, constituting the fcetal portion of 

 the placenta; m.p, maternal portion of the placenta; rf. b, decidua vera; (2. r, de- 

 cidua refleza; al, allantois. 



for the rabbit ; and, even with the preparation that Nature 

 makes for the final separation of the placenta from both fcetus 

 and mother, this event does not take place without some rupture 

 of vessels and consequent hasmorrhage. 



It is difficult to conceive of the great vascularity of the 

 human placenta without an actual examination of this structure 

 itself, which can be done after being cast off to great advan- 

 tage when floating in water; by which simple method also the 

 thinness and other characteristics of the membranes can be 

 well made out. 



The great vessels conveying the foetal blood to and from the 



