114 THE BREEDING OF ANIMALS 



110. The causes of sterility. The various causes 1 

 of sterility may be classified as anatomical, physiological, 

 pathological or psychological. Sterility in the male may 

 be due to an inability to perform the sexual act, which 

 condition is known as impotence, or it may be due to an 

 inability properly to develop spermatozoa. 



111. Causes of sterility in the male. The male may 

 be sterile as a result of undeveloped testicles as in some 

 ridglings, where the testicles are retained in the abdomen. 

 The ridgling is not always permanently sterile and may 

 be fully fertile, but the failure of the testicles to descend 

 normally from the abdominal cavity into the scrotum 

 is to be regarded with suspicion by the breeder. The 

 only way to determine whether a particular ridgling is 

 fertile is by actual trial. There is no medicinal or surgi- 

 cal treatment which can make a barren ridgling fertile. 



Bulls, boars and stallions which are fed upon a generous 

 ration of highly nutritious food and are not given regular 

 exercise tend to become over-fat, arid such a condition 

 often leads to fatty degeneration of the testicles and conse- 

 quent sterility. This condition is recognized by all suc- 

 cessful breeders. Breeding males that have proven 

 themselves of great merit as sires and are not intended 

 for exhibition are generally and wisely maintained on a 

 moderate allowance of nutritious food, being careful 

 to limit the amount and provide some means for exercise, 

 thus avoiding the almost inevitable fatty degeneration 

 of the reproductive tissues which follows long-continued 

 high feeding combined with little exercise. An example 

 of the intimate relation of these factors to fertility is to 

 be observed in the breeding practices of many modern 



1 See "Diseases of the Horse," U. S. Department of Agri- 

 culture, 1907, pp. 151-154. 



