68 Veterinary Elements. 



sows ten to twelve days. Mating will only be permitted 

 during the period of heat. The time available for mat- 

 ing also varies in animals, the average duration of heat 

 in the mare is two to three days, in the cow fifteen to 

 thirty hours, ewe two to three days, in the sow one to 

 three days. The presence of the male is often required 

 to prove the existence of the heat. If conception takes 

 place heat is not evinced again until after the birth of the 

 young. The cow will come in heat four, weeks after 

 calving, the mare nine days after foaling; in ewes, 

 except Dorsets and their crosses, breeding will not be al- 

 lowed until fall, while sows show no signs of heat until 

 after the pigs are weaned, although conception has been 

 known to take place three days after farrowing. The 

 time taken by the ovum to reach the uterus may be two 

 or three days, in rare cases after becoming impregnated, 

 the ovum has fallen into the abdominal cavity and there 

 developed. Some animals are continually in heat; such 

 is usually an evidence of a diseased condition of the 

 ovaries. Puberty in the male is evidenced by the secre- 

 tion of semen and the presence of the sexual appetite. 

 The contact of the male organ, which must be erect, with 

 the walls of the vagina causes ejaculation of the semen. 

 One single spermatozoon is sufficient to impregnate an 

 ovum, such being the case, numerous services during one 

 heat should not be permitted except in special cases. Im- 

 pregnation is as a rule only possible between animals of 

 the same species; hybrids are the result of crosses be- 

 tween different species, such as between the donkey and 

 horse, the mule being the result. IJybrids will not 

 breed. Artificial breeding by means of the capsule 



