*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 examination of the abdomen to see that it is in a fit condition for class study. If the bladder is unnaturally distended, its contents may be 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 center 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 the liver. As the liver is filled with blood, neither it nor its connecting blood vessels should be cut at this time. 4. Trace out the continuity of the canal. Find the esophagus where it penetrates the diaphragm and joins the stomach. Find next the union of the stomach with the small intestine. Then, by carefully following the coils of the small intestine, discover its union with the large intestine. 5. Within the first coil of the small intestine, as it leaves the stomach, find the _pancreas_. Note its color, size, and branches. Find its connection with the small intestine. 6. Beginning at the cut portion of the abdominal wall, lift the thin lining of the peritoneum and carefully follow it toward the back and central portion of the abdomen. Observe whether it extends back of or in front of the kidneys, the aorta, and the inferior vena cava. Find where it leaves the wall as a _double_ membrane, the _mesentery_, which surrounds and holds in place the large and small intestines. Sketch a coil of the intestine, showing the mesentery.