UMBILICAL IIEJtXIA. 705 



according as the viscus is intestine or onientuiu, or both ; thus we have 

 entcromphalus, mcscntcro- or cpiploviphalus, and entcro-cpiploniphalus. 

 The last is most frequently observed in Carnivorous animals. 



Causes. 



Wo have just alluded to the cause of congenital hernia. Acquired or 

 accidental hernia may be due to severe or sudden muscular exertion ; 

 as when the Foal or Calf runs or jumps very actively during its gambols, 

 or wiien pursued, or in falls. It is sometimes produced when the young 

 creature is separated from its parent, and being kept in an isolated 

 place, it rushes about and cries energetically. Umbilical hernia has 

 also been known to follow an attack of colic, and after constipation or 

 diarrhcca. 



There appears to be generally present, in umbilical hernia, a certain 

 organic predisposition, due to the suppressed or imperfect organization 

 of the Whartonian gelatine ; and it has been remarked that common- 

 bred animals are more liable to it than those of the higher breeds. 

 Nevertheless, in all those in which it manifests itself— no matter what 

 the breed may be — there is usually constitutional debility present, due 

 in many instances to the mother having been ill-fed and badly cared 

 for during pregnancy. Zundel says that there are years in which the 

 accident is unusually frequent, and particularly wlien much rain prevails, 

 as then the food of Herbivorous animals is more aqueous than at other 

 times. Low, wet, marshy pastures are also believed to predispose to 

 hernia ; as in them the tissues become soft and relaxed, and the 

 digestive organs inordinately bulky; Foals and Calves kept in these 

 situations have the belly voluminous, and the extrinsic pressure weakens 

 the abdominal walls. Bcnard, Hamon, Cruzel, Bouley, and others, 

 believe in heredity as a predisposing cause. Mares which were afTected 

 with umbilical hernia when young, have produced foals which presented 

 this lesion. 



Patholoijical Anatomy. 



The hernial pouch or sac is nearly always lined by peritoneum — the 

 peritoneal investment being produced at the same time as the hernia. 

 In some instances, however, the peritoneum gives way to the pressure 

 of the viscera, and then the walls of the sac are composed only of 

 connective tissue and skin. The latter is frequently so much stretched 

 that it becomes thinner, and in Puppies is generally quite transparent. 



Marlot says that the sac is usually composed of five layers: I. The 

 parietal peritoneum ; 2, A very fine fibrous layer constituted by the 

 fascia transversalis ; 3. A kind of dartos formed by the tunica abdo- 

 minalis ; 4. The panniculus carnosus muscle ; 5. The skin — the whole 

 being connected by connective tissue. But this arrangement is far 

 from being constant. The opening of the iiernial sac corresponds to the 

 umbilical opening, which is elongated, and measures in the Foal from 

 \\ to 3.1 inches in length, its width being variable, but never exceeding 

 2'inche's. The viscera contamed in the sac are usually the small 

 intestine, omentum, free colon, and the point of the caecum. Lanclot, 

 Bonard, Delafond, Ilertwig, and others, have sometimes found tlic 

 urachus in the sac, as well as intestine ; but in congenital hernia the 

 \nachu3 can scarcely fail to be absent, and we may also have the 

 lunbilical veins. It rarely happens that there is any adhesion between 

 th« hernied organs and the sac containing them, inflammation being 



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