392 OPERATIONS ON THE DIGESTIVE APPARATUS. 



Aside from other distinguishing characteristics, all hernias are 

 divisible into two classes — internal and external. Of the latter, 

 some, as the eventration, have no containing sac, while the others, 

 which have a serous covering, are in reahty alone entitled to be 

 considered as the true hernias. These, usually occurring through 

 one of the natui'al 02)eiiings, are called natural, in ojjposition to 

 the accidental, which, like the ventral hernias and the eventration, 

 occur through accidental and artificial oj)enings. Any of the ab- 

 dominal viscera, with the exception of the pancreas and the kid- 

 neys, may enter into the formation of a hernia, and as each is 

 known by the name of the displaced organ, we are given the 

 designations of enterocele for a hernia of the small intestines ; epi- 

 plocele, for that of the omentum, and entero-epiplocele of both the 

 intestines and omentum. The name of g astro-ventral is given to 

 the ventral hernia which involves with it the stomach ; cystocele, 

 when it is the bladder which is affected, and hysterocele when the 

 uterus is concerned. Hernias can be, moreover, congenital or oc- 

 casional — that is, they may exist at birth or previous to it, and 

 also when making their appearance under special causes after 

 birth. They may be also considered as acute when recent, or 

 chronic, when of long standing. 



Their originating causes are numerous, and may be said to 

 comprehend any which may predispose an animal to such a lesion 

 by contributing to an increase of the pressure which the organs 

 contained in the abdominal cavity bring to bear upon its walls, or 

 any w^eakness in the walls, which may diminish their power of re- 

 sistance to the pressure, as, for example, a condition of leanness 

 arising from a sudden or recent change from a state of obesity ; 

 blows upon the abdomen ; wounds and cicatrices of the abdomi- 

 nal vfalls ; \'iolent, jerking efforts, such as those required in com- 

 pulsory jumping or hauling, or in any other of the struggles to 

 which they are too often forced, and even when under the sur- 

 geon's hands, when, as a j^atient, the animal is cast and secured 

 for an operation ; the rapid relaxation after contraction of the 

 natural openings, repeated pressure, or excessive dilatation, as 

 with staUions used for covering mai*es, may be placed among the 

 j)redisposing causes. They have also been observed in mares, 

 after violent efforts during parturition ; also during colics and 

 other tympanitis. To recapitulate and partly to rej)eat 



The general symptoms characteristic of hernias, are compar- 



