THE CESTROUS CYCLE IN THE MAMMALIA 43 



young (as distinguished from mere sexual capacity), is a subject 

 which is dealt with more fully in a future chapter (Chapter XIV.). 



The wild goat, like the wild sheep, has a very restricted sexual 

 season,^ while, according to Low, the domesticated goat experiences 

 oestrus at very frequent periods.^ 



^ A similar statement may be made about cattle, for Heape ^ says 

 that whereas w^Jd cattle in captivity are capable of reproduction at 

 any time of the year, and experience a remarkable increase in the 

 recurrence of their dicestrous cycles, we are led to infer from the 

 limited calving season among similar animals in the wild state that 

 the sexual periods are likewise restricted. Eaciborsky* says that in 

 the more domestic types of cattle the cows receive the bull more 

 frequently than in the v^ilder breeds. Ellen berger^ states that 

 among domestic cattle the dicestrous cycle varies from about two to 

 four weeks, but Schmidt " has shown that the differences may be 

 much greater. "Wallace ^ says that oestrus recurs in summer every 

 nineteenth day, but in winter it may not recur oftener than every 

 twentieth or every twenty -first day. Usually the cow seeks the bull 

 again four or five weeks after calving. Shortt,* however, states that 

 in India this does not occur until after six or nine months. Blood 

 is not infrequent in the external discharge of cows and heifers, but 

 such discharge does not usually appear until after oestrus is over. 

 Emrys-Eoberts ® has described the internal generative organs of a 

 prooestrous cow as containing a watery secretion tinged with blood. 

 The secretion was found to contain far less mucin than during the 

 anoestrous period.^" 



The period of gestation in cattle is about nine months, but it is 

 slightly variable. 



According to Heape, who has collected evidence from various 

 authorities, the ibex, markhor, barasingha, and Hemitragus Jerulaicus 

 in Cashmir, as well as the American bison, black-tailed deer in 

 Montana, red-deer, fallow-deer, and roe-deer," and several antelopes 



'" Lydekker, loc. cit. 



^ Low, The Domesticated Animals, London, 1845. 



' Heape, loc. cit. 



* Eaciborsky, Traite de Menstruation, Paris. 



* Ellenberger, loc. cit. 



° Schmidt, " Beitrage zur Physiologie der Brunst beim Rinde," Dissertation, 

 Zurich, Munclien, 1902. 



'' Wallace (R.), loc. cit. 



' Shortt, ^1 Manual of Indian Cattle and Sheep, 3rd Edition, Madras, 1889. 



° Emrys-Roberts, " A Further Note on the Nutrition of the Early Embryo, 

 etc.," Proc. Roy. Soc, B., vol. Ixxx., 1908. 



1" According to Emrys-Roberts, the profuse mucinous secretion during the 

 prooestrum in the Mammalia is derived, not from the body of the uterus, but 

 from the cervix and vagina. 



" There has been some controversy regarding the breeding season and 

 period of gestation in roe-deer. According to Bischofif {Entwicklungsgeschichte 



