ORGANS AND PROCESSES OF DIGESTION 169 



Sketch a general outline of the cavity, and locate in this outline its 

 chief organs. 



Where it is desirable to learn something of the actual structure of the 

 digestive organs, the dissection of the abdomen of some small animal is 

 necessary. On account of unpleasant features 

 likely to be associated with such a dissection, 

 however, this work is not recommended for im- 

 mature pupils. 



Dissection of the Abdomen. (Optional) 

 For individual study, or for a small class, a 

 half-grown cat is perhaps the best available 

 material. It should be killed with chloroform, 

 and then stretched, back downward, on a board, 

 the feet being secured to hold it in place. 



The teacher should make a preliminary ex- 

 amination of the abdomen to see that it is in a FIG. 75. Model for 

 fit condition for class study. If the bladder is demonstrating the abdo- 

 un naturally distended, its contents may be men and its contents, 

 forced out by slight pressure. The following 



materials will be needed during the dissection, and should be kept near 

 at hand : a sharp knife with a good point, a pair of heavy scissors, a 

 vessel of water, some cotton or a damp sponge, and some fine cord. 

 During the dissection the specimen should be kept as clean as possible, 

 and any escaping blood should be mopped up with the cotton or the 

 sponge. The dissection is best carried out by observing the following 

 order : 



1. Cut through the abdominal wall in the cente'r of the triangular 

 space where the ribs converge. From here cut a slit downward to the 

 lower portion of the abdomen, and sideward as far as convenient. 

 Tack the loosened abdominal walls to the board, and proceed to study 

 the exposed parts. Observe the muscles in the abdominal walls, and 

 the fold of the peritoneum which forms an apron-like covering over the 

 intestines. 



2. Observe the position of the stomach, liver, spleen, and intestines, 

 and then, by pushing the intestines to one side, find the kidneys and 

 the bladder. 



3. Study the liver with reference to its location, size, shape, and 

 color. On the under side, find the gall bladder, from which a small tube 

 leads to the small intestine. Observe the portal vein as it passes into 



