26 General Principles of Veterinary Medicine, 



generated and become extinct by persistent in-and-in breed- 



ing. 



In sheep the effects are to prodnce fine and delicate ex- 

 tremities, to bare the head of wool, ana to render the ears 

 thin and red. The animal becomes very susceptible to cold, 

 and uncommonly subject to such diseases as flukes and foot 

 rot. 



THE EEPEODUCTIVE ACTS. 



In regard to the development of the reproductive powers, 

 the domestic animals differ widely. 



The mare begins to breed at four years of age and carries 

 her young 340 days from the time of conception to its natu- 

 ral delivery. She may safely be worked to within tw^o weeks 

 of that time, but should have rest for three or four weeks 

 afterwards. The foal should be weaned at five or six months 

 of age. 



The youngest age at which the heifer should be put to the 

 bull is laid down by the best English breeders at one year 

 and eight months. She carries her young the same length 

 of time as the human female, to wit, about nine months. 

 The most favorable period for calving is in the spring. For 

 ^vQ or six weeks previous to its occurrence her milk should 

 be dried, and during the whole period of gestation, she 

 should be underfed rather than overfed, too rich diet being 

 a very common cause of abortion. The calf should have 

 nothing but the teat for three or four weeks, when it may 

 begin wdth skimmed milk, etc. 



Both rams and ewes are ready to breed at fifteen months 

 of age. The ewe carries her young one hundred and fifty- 

 two days. When born, it is often very delicate and requires 

 the attentive care of the shepherd to survive. 



The sow should breed at one year of age. Her period of 

 gestation is 113 days, and it is a prudent precaution to sepa- 



