INGUINAL HERNIA IN THE HORSE. 539 



(1.) INGUINAL HERNIA IN THE HORSE. 



In stallions the inguinal canal consists of a flat funnel-shaped passage 

 about 4 inches in length, whose upper opening (annulus abdominis) is 

 from f to 1£ inches in length, but occasionally much wider. It extends in 

 an oblique direction from behind outwards and forwards, is situated 1 to 

 2 inches from the oblique branch of the os pubis, and 4 to 6 inches from 

 the linea alba. The vessels supplying the posterior portion of the abdominal 

 walls pass about § of an inch from its posterior angle, and on its inner side. 

 The inguinal ring or outer abdominal ring (annulus inguinalis) consists 

 of a slit between the inner and outer tendinous heads of the external oblique 

 abdominal muscle, whose posterior inner angle lies 1J inches in front of 

 the os pubis, and somewhat further from the middle line of the abdomen. 

 The anterior inner wall of the inguinal canal is largely formed by the inner 

 oblique abdominal muscle, the outer by the crural arch or Poupart's 

 ligament. 



Causes. In stallions with abnormally wide abdominal rings, 

 and less frequently in geldings, the small intestine or omentum may 

 enter the inguinal canal. According to Berdez, Vogel, Stockfleth, 

 and others, the condition is always caused by excessive width of the 

 ring ; whilst Lafosse, H. Bouley, and Gerlach declare that inguinal 

 hernia may occur even where the aperture is of normal width. But 

 even if we allow this, there is no doubt that in by far the greater 

 number of cases the condition is due to abnormal width of the ring, 

 which sometimes measures 4 to 6 inches. Moller has, however, 

 also seen inguinal hernia in horses in which the inner ring scarcely 

 allowed the entrance of two fingers, though, as a rule, two easily 

 pass in addition to the spermatic cord. It is therefore difficult to 

 fix a normal width and settle this question, which requires numerous 

 measurements to be made in different races of animals. Inguinal 

 hernia is generally congenital, or appears during the descent of the 

 testicle. The tendency to it seems to be inherited. Its production 

 is favoured by all circumstances which cause increased abdominal 

 pressure, such as tympanites, severe exertion, hard drawing on soft 

 ground (where the action of the muscles in lifting the feet also produces 

 dilatation of the abdominal ring), or struggling in hobbles. Ham- 

 merschmid's case shows that difficult birth may produce inguinal 

 hernia in the foal, particularly in delivery with the hind-quarters 

 presented ; the foal in question showed an inguinal hernia as large 

 as a child's head on the third day after birth. All movements which 

 cause dilatation of the abdominal ring, like violent kicking or slipping, 

 especially slipping outwards and backwards, may give rise to inguinal 

 hernia. The same result may be produced by dragging on the 

 spermatic cord during castration, by the pull of a heavy clam, or of 



