328 



THE CAT. 



[chap. X, 



through which nourished and oxygenated blood is conveyed to the 

 foetus, and its importance continues till birth. The estabhshment of 

 pulmonary respiration, however, and the acquisition of the power of 

 taking nourishment by suction, do away with all need for the 

 placenta, and, by consequence, for its stalk, the umbilical cord, 

 which is gnawed across by the mother on the Idtten's birth. The 



Fig. 150. — FCETUS IN UTERO (BUFFON AND DaUBENTON), SHOWINO THE FtETUS ENVELOPED IN ITS 



Amnion, and with its zonaky Placenta and spindle-shaped Umbilical Vesicle. 



a. Chorion. 



7). Tlic z<)ii,ir>' planenta. 



(I. Umbilical vesicle. 



/, /. Its eluiiKatcil extremities. 



'J. The vitelline duct. 



7i. The sac, of the •amnion. 

 k. The fcetiis. 

 The short umbilical cord is showai passing from 

 the aliddiiieii of the cnilnyo to the idacentii, 

 and immediately |,'iviii;{ forth its vessels, 

 forwards and backwards, into the placenta. 



part left in connexion with the abdominal wall soon shrivels up, 

 dries, and falls off, but a permanent mark of its place of attachment 

 persists throughout life as the umbilicus or navel. 



Such being the form and arrangement of the fecial membranes 

 and adjuncts, the embryo or f(i:tus itself gradually and in a round- 

 about way assumes the image of the kitten in the mode already 

 intimated, and which will be more fully explained in describing the 

 development of the several organs. 



The period of gestation is fifty-five or fifty-six days. The ovum 

 having by that time attained its full intcr-uterine development, 

 vigorous contractions of the muscular walls of the uterus ensue, 

 while the os uteri dilates. The embryo is thus expelled from the 



