24 8 PRACTICAL ANATOMY. 



3. Three Divisions of the Colon. The divisions of the colon are ascending, 

 transverse, descending, sigmoid, and rectum. The ascending colon extends from 

 the right iliac fossa to the hepatic flexure. The transverse colon extends from 

 the hepatic flexure to the lower margin of the spleen the splenic flexure. The 

 descending colon extends from the splenic flexure to the brim of the pelvis. 



Notice the manner in which the three parts of the colon are held in place. 

 The meso-colon of the transverse is quite long ; that of the ascending and 

 descending is very short; in fact, the nature of the union is oneof adhesion 

 rather than mesenteric, in the two latter. Folds of peritoneum that bind organs 

 to walls are called mesenteries. The continuation of the descending colon below 

 the pelvic brim, to a point opposite the second piece of the sacrum, is called the 

 sigmoid. Lift it up and see the great length of its mesentery called meso- 

 sigmoid. 



4. Differential Diagnosis Between Large and Small Intestine. Inflate the 

 large intestine (Fig. 175) and see the following differential points possessed by 

 large intestine but not possessed by small intestine : (i) Fatty masses. (2) Longi- 

 tudinal muscular bands, three in number, and at equal distances from each other. 

 Each will lead to the appendix. (3) Sacculations, produced by contraction exerted 

 by the longitudinal bands. 



5. Jejunum, Ileum, and their Mesentery. Compare your dissection with fig- 

 ure 175 and you will observe that the three parts of the colon almost surround 

 the large central mass of small intestine. Collect this mass in your hands and 

 find the upper end of the jejunum going through the transverse meso-colon oppo- 

 site the third and fourth lumbar vertebra to become duodenum ; the lower end 

 you will find near the right iliac fossa, ending in the caecum, forming therewith a 

 junction called the ileo-caecal junction. Lift the whole mass of small intestine 

 upward, to estimate the length of the mesentery. 



6. The Duodenum. Turn the transverse colon and great omentum upward. 

 Find the beginning of the jejunum and shut the same off the intestine below 

 this point by a ligature. Now inflate the alimentary canal above this point i. ?., 

 duodenum and stomach. You will now see the transverse part of the duodenum 

 passing behind the superior mesenteric artery and vein. 



7. Ccecum and Appendix. You will find the caecum, as a rule, in the right 

 iliac fossa. Its rneso-caecum may be long in one case and short in another. 

 The longitudinal bands traced downward will lead to the appendix. This organ 

 has a peritoneal ligament the meso-appendix. It may occupy a variety of 

 locations. It may hang down in the pelvis across the brim. Its usual posi- 

 tion is in an angle between the ileum and the pelvic side of the caecum. 



A general review will now be made of what you have examined in situ and 

 studied in the normal position without cutting. 



1. You saw, on opening the abdomen, the walls and also the viscera (organs), 

 covered by a very thin, smooth, and glistening membrane peritoneum. The 

 layer covering the walls above, below, in .front, behind, and on the sides is 

 called parietal peritoneum ; that covering the organs themselves is called 

 visceral peritoneum. The space between these two layers is the peritoneal cavity, 

 which contains only a small amount of serum for lubrication. Henceforth you 

 will define a peritoneal cavity as a space between a visceral and a parietal layer 

 of peritoneum. (Fig. 171.) 



2. On the interior of the abdominal walls you saw, through the thin parietal 



