724 DISEASES AND ABNORMALITIES. 



Mares which were affected with umbilical hernia when young, have pro- 

 duced foals which presented this lesion. 



Pathological 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 abdomi- 

 nalis ; 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 hernial sac corresponds to the 

 umbilical opening, which is elongated, and measures in the foal from i^ 

 to 3^ inches in length, its width being variable, but never exceeding two 

 inches. The viscera contained in the sac are usually the small intestine, 

 omentum, free colon, and the point of the caecum. Lanclot, Be'nard, 

 Delafond, Hertwig, and others have sometimes found the urachus in the 

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

 scarcely fail to be absent, and we may also have the umbilical veins. It 

 rarely happens that there is any adhesion between the hernied organs 

 and the sac containing them, inflammation being rare ; the sac seldom 

 indeed contains any serum, and is therefore in immediate contact with 

 the misplaced viscera. When ascites is present, however, serous fluid 

 may then be present, and constitute the diseased condition termed 

 " hydro-enteromphalus." 



Symptoms. 



The symptoms of umbilical hernia are, as a rule, entirely local. There 

 is a round or pyriform tumor situated in the region of the umbilicus or 

 *' navel," varying in size in different individuals and species — from that 

 of a pigeon's egg to a child's head, or even larger. The siz-e also varies 

 in the same individual at different times, according as the digestive 

 organs are full or empty, the attitude standing or recumbent, at rest or 

 undergoing active exertion, or the duration of the hernia — the older it is, 

 the larger the tumor. It is usually soft, fluctuating, easily depressed by 

 the finger, and as readily resuming its ordinary size and shape ; when 

 recent, however, it is often tense and not depressible. Sometimes it has 

 a doughy feel and fluctuates much, and at other times it is flaccid, accord- 

 ing as the portion of intestine which it contains is empty or filled with 

 alimentary matters. It is nearly always indolent, and in the large 

 majority of cases can be reduced by throwing the animal on its back, by 

 manipulation externally, or by taxis internally. The tumor soon returns, 

 however, particularly when the animal lies down or moves about ; closing 

 the nostrils or causing the animal to cough, will also produce its imme- 

 diate appearance. 



When the sac has been emptied by pressure or taxis, the opening in the 

 abdomen can then be perceived. As a general rule, the volume of the 

 tumor corresponds to the dimensions of this opening, which is sometimes 

 elliptical, at other times nearly or completely circular ; in false or acci- 



