HEKNIA. 385 



If tlie escape of the fluid shoiild stop or diminish, a blunt 

 stylet can he introduced into the canula to clean it of any albu- 

 minous or epiploic mass which may obstruct it. The operation in 

 small animals is performed in the same manner. 



As the removal of the entire accumulation of the fluid is dan- 

 gei'ous, though less so than in thoracentesis, it is better to permit 

 a portion of it to remain. The quantity is sometimes enormous, 

 ranging between thirty-five and ninety-six quarts. After the 

 quantity desired has been obtained, the canula of the trocar is 

 carefully withdrawn, and a bandage or roller of adhesive plaster 

 placed aroimd the body of the animal. 



Among accidents possible in this operation, wounds of blood- 

 vessels or of the intestines, and fatal peritonitis may be men- 

 tioned. 



HERNIA. 

 General View. 



In a general sense, any tumor formed by the entire or partial 

 escape and j)rotrusion of an organ, either wholly or in part, from 

 the restraining tension of the integuments, or from the cavity 

 which forms its normal location, is a hernia, or in popular phrase, 

 a rupture. The more special appHcation of the term is to the dis- 

 placement of the abdominal viscera, but it is also employed to 

 describe the enceplialocele, or protrusion of the brain through the 

 cranium; the projection of the iris and \h.Q jabot, or protrusion of 

 the oesophagal mucous membrane, through its muscular covei'ings. 

 And again the prominence of a synovial membrane beyond its 

 ordinary bounderies: that of a muscle through its aponeurotic 

 envelope ; the prolapsus of the rectum ; of the vagina ; of the 

 uterus, etc., etc., — these also receive the same designation and are 

 recognized members of the hernia family. We shall, in the pres- 

 ent chapter, mainly limit our consideration to the disjjlacements of 

 the abdominal digestive organs. 



The rationale of the formation of a hernia becomes a matter 

 of easy comprehension, when we take into consideration the gen- 

 eral anatomy of the abdomen, and especially the structure of its 

 inferior wall. The muscular layers which form the exterior wall 

 of this large splanchnic canity are not of equal density through 

 their whole extent, and consequently do not offer in every part an 

 equal amount of resistance to the outward pressure of the interior 



