328 



THE CAT. 



[CHAP. x. 



through, which nourished and oxygenated blood is conveyed to the 

 foetus, and its importance continues till birth. The establishment 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 kitten's birth. The 



Fig. 150. FffiTUS IN UTERO (BUFFON AND DAUBENTON), SHOWING THE FtETUS ENVELOPED IN ITS 



AMNION, AND WITH ITS ZONARY PLACENTA AND SPINDLE-SHAPED UMBILICAL VESICLE. 



a. Chorion. 



&. The zonaiy placenta. 



d. Umbilical vesicle. 



/, /. Its elongated extremities. 



(j. The vitelline duct. 



h. The sac of the amnion. 

 A:. The foetus. 



The short umbilical cord is shown passing from 

 the abdomen of the embryo to the placenta, 

 and immediately giving 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 foetal membranes 

 and adjuncts, the embryo or FCETUS 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 inter-uterine development, 

 vigorous contractions of the muscular walls of the uterus ensue, 

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



