152 BUEEAU OF ANIMAL INDUSTRY. 



STERILITY. 



Sterility ma}' be in the male or in the female. If due to the .stallion, 

 then all the mares put to him remain barren; if due to the liiare, she 

 alone fails to conceive. 



In the stallion sterility may be due to the following causes: (a) 

 Imperfect development of the testicles, as in cases in which they are 

 retained within the abdomen; (h) inflammation of the testicles, result- 

 ing in induration; (c) i'dtty degeneration of the testicles, in stallions 

 liberally fed on starchy food and not sufficiently exercised; (d) fatty 

 degeneration of the excretoiy ducts of the testicles {vasa defereniia); 

 {e) inflammation or ulceration of these ducts; {/) inflammation or 

 ulceration of the mucous membrane covering the penis; {(/) injuries 

 to the penis from blows (often causing paralysis); (A) warty growths 

 on the end of the penis; (/) tumors of other kinds (largely pigmentary), 

 affecting the testicles or penis; (_/) nervous diseases which abolish the 

 sexual appetite or that control the muscles which is essential to the 

 act of coition; (/•) azoturia with resulting weakness or paralysis of 

 the muscles of the loins or the front of the thigh (above the stifle); 

 (l) os'sification (anchylosis) of the joints of the back or loins, which 

 render the animal unable to rear, or mount; (m) spavins, ringbones, 

 or other painful affections of the hind limbs, the pain of which in 

 mounting causes the animal to suddenly stop short in the act. In the 

 first three of these only ( a, h, and c) is there real sterilit}'^ in the sense 

 of the nondevelopment or imperfect development of the male vivify- 

 ing element (spermatozoa). In the other examples the secretion may 

 be perfect^in kind and amount, but as copulation is prevented it can 

 not reach and impregnate the ovum. 



In the mare barrenness is equally due to a variety of causes. In a 

 number of breeding studs the proportion of sterile mares has varied 

 from 20 to 40 per cent. It may be due to: (a) Imperfect development 

 of the ovary and nonmaturation of ova; (l) cystic or other tumors of 

 the ovary; (c) fatty degeneration of the ovary in ver}'' obese, pampered 

 mares; (d) fatty degeneration of the excretory tubes of the ovaries 

 (Fallopian tubes); {c^ catarrh of the womb, with nuicopurulent dis- 

 charge; (/) irritable condition of the womb, with profuse secretion, 

 straining, and ejection of the semen; {(/) nervous irritability, leading 

 to the same expulsion of the male element; (/<) high condition (ple- 

 thora), with profuse secretion and excitement; (?) low condition, with 

 imperfect maturation of the ova and lack of sexual desire; (J) poor 

 feeding, overwork, and chronic debilitating diseases, as leading to the 

 condition just named; {/c) closure of the neck of the womb, tempora- 

 rily b}' spasm or permanently by inflammation and induration; (/) clo- 

 sure of the entrance to the vagina through imperforate h3'men, a rare, 

 though not unknown, condition in the mare; (r/i) acquired indisposition 

 to breed, seen in old, hard-worked mares which are first put to the 



