DRiESTIVE SYSTEM. 243 



render their descriptions definitive) to divide the cavity artificially ; 

 and they have done this by drawing certain imaginary lines over 

 its superficies^ which are supposed, by means of imaginary planes 

 let down perpendicularly from them, to intersect or partition the 

 cavity into so many compartments, to which the name of regions 

 has been assigned. 



The primary and grand division of the abdomen is into three 

 regions — the anterior, or epigastric; the middle, or umbilical; 

 and the posterior, or hypogastric. 



TsiE EPIGASTRIC REGION is the space comprehended be- 

 tween the ensiform cartilage and an imaginary line drawn across 

 the abdomen, posteriorly to the cartilages of the false ribs: it is 

 subdivided into three others — the scrobiculus cordis, the space 

 included between the ribs; and the right and left hypochondria, 

 the lateral cavities or boundaries of it. 



The umbilical region extends in breadth from the linejust 

 mentioned to another drawn across from one anterior spinous pro- 

 cess of the ileum to the other: it is equally subdivided into three 

 others by tranverse lines, the middle of which retains the name 

 of umbilical region, while the lateral are called the lumbar 

 regions. 



The hypogastric region extends over the remainder of 

 the belly- It is also subdivided into three: the part included 

 between the spinous processes of the ilea and the pubes receives 

 the name of regio pubis ; the lateral subdivisions, of iliac regions. 



The abdominal viscera of the horse differ from those of the 

 human subject chiefly in the shape and comparative size of the 

 stomach and the colon : their general relative situation and con- 

 nexion we shall find to be much the same in both. 



Having opened the cavity of the abdomen, by making a crucial 

 incision through its muscular parietes, we perceive that its inte- 

 rior, and the viscera lying within it, present an uniform glisten- 

 ing surface; are smooth, polished, humid, and slippery to the 

 feel ; and are bedewed with a limpid exudation : all which arises 

 from their possessing a general investing membrane of the same 

 (serous) class as the pleura, and which appeaijs, in most respects, 

 to perform similar uses. To this part the name of peritoneum 

 has been given. 



Peritoneum. 



The peritoneum is the membrane, then, that lines the cavity of 

 the abdomen, and is reflected upon the contained viscera. When 

 I introduce my hand into the belly, cvciy surface I apply it to 

 being covered by peritoneum, 1 am not, in truth, able to actually 



