STERILITY 115 



owners of draft stallions as compared with the methods 

 of early stallioners in the newer agricultural sections of 

 the United States. It was formerly the custom to drive 

 or ride the stallion from farm to farm, thus often covering 

 a territory of 100 to 200 square miles. Stallions so handled 

 were notoriously sure foal-getters and not infrequently 

 were successful in getting from eighty-five to ninety-five 

 per cent of the mares in foal. The modern plan of 

 keeping the draft stallion in high condition and stand- 

 ing him for service at one barn, thus requiring all mares 

 to come to him, has undoubtedly reduced the fertility 

 of draft stallions. It is no unusual event for a draft 

 stallion so managed to get only sixty per cent of mares in 

 foal, while seventy-five per cent of the mares in foal is 

 regarded by some stallioners as a fair average for stal- 

 lions handled in this manner. The fatty degeneration 

 of the vasa deferentia or excretory ducts of the tes- 

 ticles is also a not infrequent cause of sterility in very 

 fat animals. 



Any injury or deformity of the penis which renders 

 the act of copulation painful or impossible is to be included 

 in the category of anatomical causes of sterility. In 

 this class may be included inflammation or ulceration 

 of the mucous membrane enclosing the penis, paralysis 

 of that organ, and the presence of tumors on the penis 

 itself or its appendages. Muscular and bone diseases 

 which in any way interfere with the exercise of the breed- 

 ing function are causes of barrenness. Spavin or ring 

 bone may cause the stallion such inconvenience and dis- 

 tress in mounting as to prevent copulation and thus indi- 

 rectly be a cause of barrenness. Similarly, diseases of the 

 muscles of the back and loins may be responsible for 

 sterility in certain individuals. Diseases of the brain 



