THE STOMACH 463 



while lymphatics are abundant in the visceral layer ; they are independent, or 

 form a sheath around the blood-vessels of the mesentery. Its nerves come from 

 the diaphragmatic, lumbjir, and intercostal branches, and the great sympathetic. 



Differential Characters in the Abuominal Cavity of the other Animals. 



In the Carnivora, the abdominal cavity is very narrow; while in Ruminants it le very 

 vast, its capacity being in direct relation to the volume of the viscera it contains. 



The general arrangement of the peritoneum varies but little in the diflferent species, ihe 

 only notable diversities being reii\arked in the great omentum. In the Ox, Sheep, and 

 Goat, this is detached from the middle of the lower face of the rumen, and envelops the right 

 sac of that organ, fixing the fourth compartment to its great curvature, and then passing: upwards, 

 to become continuous with the mesentery. In the Dog and Pig, this fold descends in front 

 of the intestinal mass, until near the pelvis ; then it ascends in gathering on itself, and 

 ultimately spreads over the colon ; in the middle portion of the great omentum there are, 

 consequently, four layers laid against each other. 



Comparison of the Abdominal Cavity of Man with that op Animals. 



The abdominal cav.ity of Man is elongated vertically, and has an inferior cavity occupying 

 the entrance to the pelvis. There is nothing particular to note in its disposition, the differences 

 observed in it being allied to tiie external shape of the body. The peritoneum is spread over 

 its parietes nearly in the same manner as in the Carnivora ; the great omentum is formed by 

 four layers, and covers the intestines like an apron ; between its two layers is the lesser cavity 

 of the omentum, virtually in the adult. * 



The Stomach. 



The stomach is a membranous sac placed between the oesophagus and 

 intestines, and in which is completed the division of the alimentary matters. 



1. The Stomach in Solipeds (Figs. 258, 259, 260, 261) 



Preparation. — In order to study the relations of this organ, it sufiBces to open the abdomen 

 and remove the intestinal mass in the following manner : Place the animal in the first 

 position, ami very slightly inclined to the left side; make an incision through the inferior 

 abdominal wall, or. still better, carry it away entirely by a circular incision, taking cure not 

 to wound any part of the intestine. The entire viscera should then be wiih(h-awn from tlie 

 abdominal cavity, and laid on the table which supports the subject; for this mass cannot be 

 allowed to fall on the ground without risk of being pulled and torn, either in the intestine 

 itself, or those parts wliich it is desired to preserve intact in the abdomen. Incise tlie floating 

 colon wlicre it joins the rectum, and the duodenum where it passes behind the great mesenteric 

 artery; the base of the caecum should now be detached from the sublumbar surface by the 

 rupture of the connective tissue which connects it to the right kidney and the pancreas; the 

 cellular connection between the latter gland and the terminal extremity of the fourth portion 

 of the large colon should also be broken ; after this, it is only necessary to divide the attach- 

 ment of the mesenteric bands to the sublumbar region, with the vessels contained between 

 them. The intestinal nias:^ is then definitely expelled from the abdominal cavity. In this 

 way it is possible to expose, and conveniently prepare, not only the stomach, but also the 

 spleen, liver, pancreas, kidneys, ureters, etc. Nothing more remains than to make known the 

 procedure to be adopted in everting the stomach, in order to study its internal surface, or 

 dissect its deep muscular layer. It is recommended, first, to excise the stomach with at least 

 three inches of the oesophagus, and eight inches of the duodenum, and cleanse the interior of 

 the organ. This may be done in several way?, but the following is the simplest : a certain 

 quantity of water is introduced into the stomach by fixing the duodenum to a water-tap, the 

 right hand manipulating the organ while the left closes the duodenum to prevent the escape 

 of the liquid. The alimentary substances contained in it are in this way mixed with the 

 water, and may be expelled from the duodenum by pressing the stomach ; this operation, being 

 repeated four or five times, thoroughly cleanses the cavity of the organ. To evert the inner 

 surface, it is only necessary to introduce by the duodenum a loop of wire, and make it pass 

 through the oesophagus ; a strong waxed thread is fastened in the loop and firmly fixed around 



