X PRACTICAL DIRECTIONS 529 



3. a, The small posterior mesenteric- artery, leaving the aorta z, short 

 distance posteriorly to the left kidney and supplying the rectum ; b, the 

 posterior mesenteric vein, in the mesentery of the rectum. 



III. Turn the intestines over to the animal's left side and spread out 

 the duodenum, putting its mesentery slightly on the sketch but taking 

 care not to rupture it, so as to make out — 



1. a. The large anterior mesenteric vein, into which the posterior 

 uieeenteric vein opens ; b, the pancreas and its duct, opening into the 

 distal limb of the duodenal loop an inch or so beyond the bend. 



2. a. The right kidney, partly overlapped by the caudate lobe of the 

 liver, and its ureter ; b, the right adreiial. 



IV. Replace the intestines in their natural position ; cut through the 

 gullet close to the diaphragm, draw the stomach backwards, turn for- 

 wards the lobes of the liver, and dissect out the following structures 

 (Fig. 127) :— 



1. The common bile-duct — made up oi cystic and hepatic ducts, and its 

 entrance into the duodenum. 



2. a, The large hepatic portal vein, running in the mesentery ventrally 

 to the postcaval, made up by the union of the mesenteric, gastric, 

 and splenic veins, and entering the liver, sending a branch to each lobe ; 

 b, the transparent lymphatic vessels (lacteals) in the mesentery. 



V. Tie two pieces of thread, about half-an-inch apart, rouiid the portal 

 vein just before it enters the liver (the hepatic artery and bile-duct may 

 be included in the ligature) ; cut through the rectum just anterior to the 

 pelvic cavity, and through the portal vein between the ligatures, as well 

 as through the mesenteric attachments of the stomach and intestine, 

 and remove them from the body entire. Unravel the intestine by 

 cutting or tearing the mesentery— except that part of it in which the 

 pancreas lies — and spread it out on the dissecting-board or in a large 

 dissecting dish, arranging it so that the various subdivisions may easily 

 be distinguished from one another. In addition to the relations of 

 these, note : — 



1. The sacculus rotundas (Fig. 125, s. r), and the characters of the 

 ciecum, which proximally passes insensibly into the colon. 



2. The length of the intestine as a whole (about fifteen or sixteen 

 times that of the animal), and the relative lengths of the five divisions. 



Sketch the entire canal. 



VI. Remove and cut open the stomach and parts of the small intes- 

 tine, colon, and rectum : wash thoroughly, and exainine under water. 



Pract. Zool. M M 



