152 DISEASES OF THE HORSE. 



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; (6) inflammation of the testicles, re- 

 sulting in induration; (c) fatty degeneration of the testicles, in stal- 

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

 fatty degeneration of the excretory ducts of the testicles (vasa defe- 

 rentia)', (e) inflammation or ulceration of these ducts; (/) inflam- 

 mation 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; (z) tumors of other kinds 

 (largely pigmentary), affecting the testicles or penis; (_/') nervous 

 diseases which abolish the sexual appetite or that control the muscles 

 which are essential to the act of coition; (k) azoturia with resulting 

 weakness or paralysis of the muscles of the loins or the front of the 

 thigh (above the stifle) ; (I) ossification (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, 6, and c) is there 

 real sterility in the sense of the nondevelopment or imperfect devel- 

 opment of the male vivifying 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 

 numlH'r of breeding studs the proportion of sterile mares has varied 

 from i!0 to 40 per cent. It may be due to: (a) Imperfect develop- 

 ment of the ovary and nonmaturation of ova; (b) cystic or other 

 tumors of the ovary; (c) fatty degeneration of the ovary in very 

 ol>ese, pampered mares; (d) fatty degeneration of the excretory 

 tubes of the ovaries (Fallopian tubes) ; (e) catarrh of the womb, 

 with mucopurulent discharge; (/) irritable condition of the womb, 

 with profuse secretion, straining, and ejection of the semen; (g) 

 nervous irritability, leading to the same expulsion of the male ele- 

 ment; (A) high condition (plethora), with profuse secretion and 

 excitement; (/) low condition, with imperfect maturation of the ov;i 

 and lack of sexual desire; (j) poor feeding, overwork, and chronic 

 debilitating diseases, as leading to the condition just named; (k) 

 closure of the neck of the womb, temporarily by spasm or perma- 

 nently by inflammation and induration; (I) closure of the entrance 

 to the vagina through imperforate hymen, a rare, though not un- 

 known, condition in the mare; (m) acquired indisposition to breed, 

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

 when aged; (;i) change of climate has repeatedly been followed by 

 barrenness; (o) hybridity, which in male and female alike usually 

 entails sterility. 



