42 THE BREEDING OF ANIMALS 



period are so closely associated that the stimulus, what- 

 ever it may be that causes the one, will probably under 

 normal conditions directly or indirectly cause the other. 



Heape has maintained that since it is known that, 

 in various animals, either menstruation or oestrus may 

 take place without ovulation, and that ovulation may 

 occur without the coincidence of menstruation (Leopold 

 and Mironoff, 1894) or of oestrus (fat), the possibility of 

 isolating these functions is demonstrated. Thus it is 

 no longer impossible to suppose that, while they are 

 both due to similar stimulating influences, one of them 

 may be developed in excess of the other. 1 



It is probable that heat may sometimes occur with- 

 out the production of an egg, and it is possible that the 

 production of an egg may not always be accompanied by 

 heat, but when such a condition exists, it is to be regarded 

 as the exception and not the rule. It is very clear that 

 the oestrum and ovulation are influenced by nutrition. 

 An insufficient supply of food, deficient in the essential 

 elements required for the normal development of animals, 

 retards the first appearance of heat in young animals and 

 causes irregular periods in mature animals. Breeders 

 of live-stock have long known that the oestrum can 

 be materially influenced by the method of feeding. 

 Skillful stockmen feed the females in such a manner 

 as to cause them to be " gaining " at mating time. This 

 is accomplished by richer feeding or turning to fresh 

 grass. 



43. Artificial insemination. The transfer of the 

 semen of the male to the uterus of the female by the aid 

 of instruments or capsules is known as artificial insemina- 

 tion or, more commonly among practical breeders, as 



1 Heape, loc. cit., p. 34. 



