360 Veterinary Medicine. 



gans only, and as it is considered irremediable \iy surgical 

 measures, it may be properly considered in the class of medical 

 affections. 



Definitio7i. A displacement of one or more of the abdominal 

 organs into the cavity of the throax. 



Frequeyicy iji different animals. It has been found most fre- 

 quently in the horse, and less so in the dog and ox. Severe 

 exertions conduce to it in horse and dog, while in the ruminant 

 the great bulk of the gastric cavities, covering the whole pos- 

 terior surface of the diaphragm, tends to prevent protrusion even 

 if a slight rupture has taken place. On the other hand, the 

 weight of the gastric cavities in the ox and tlie tension upon the 

 oesophagus, when the animals ride each other, sometimes cause 

 laceration of the foramen sinistrum and hernia of the reticulum. 



Hernial mass in different animals. In the horse the protruding 

 organ is most connnonl}^ the small intestine ( enterocele), omen- 

 tum (epiplocele), colon, or less frequently the caecum, stomach 

 (gastrocele), or liver (hepatocele. In the ox the reticulum most 

 commonly protrudes, and after that the liver, abomasum, the 

 omentum or the small intestine. In the dog the mass is usually 

 formed by the stomach or liver, or less frequently by the small 

 intestine or omentum. 



Causes and mode of formation. The hernia is either congenital 

 or acquired after birth. Again, it ma}- result from imperfect de- 

 velopment or from a trauma. Congenital cases usually depend 

 on an arrest of development, the foramen sinistrum fails to close 

 and the abdominal organ passes through h\ the side of the 

 oesophagus into the chest ; or the diaphragm is left imperfect at 

 some other point, and the two cavities, abdominal and thoracic, 

 communicate. In .some instances there is left not a distinct 

 opening but a mere relaxation of the parts and under traction, as, 

 for example, by the gullet, an orifice is torn and a hernia pro- 

 trudes. vSuch cases are very rare. Other lacerations may be 

 almost all referred to external injuries on the posterior ribs, vio- 

 lent muscular exertions, sudden shocks in connection with falls, 

 or throwing for operations, and overdistension of the abdominal 

 viscera. 



I St. External Violence. In the larger animals this may come 

 from blows on the last ribs, by poles or shafts of carriages, the 



