Mammalia. 131 



large intestine, the rectum, and sever it. Remove the stomach 

 and intestines, carefully cutting the mesentery along its whole 

 attachment to the intestine, and uncoil the latter. How many 

 times is the length of the body, including the head, contained 

 in the length of the intestine ? Compare the lengths of the small 

 intestine, cecum, and large intestine. Cut out about an inch of 

 the small intestine in the middle of its course, slit it open length- 

 wise, wash it thoroughly, and examine, under water, its inner surface 

 with a lens, to see the threadlike projections, or villi. In the 

 same way examine a piece of the large intestine. These points 

 may be made out in the intestine of a dog, or from specimens of 

 the calf's intestine obtained from the butcher. Tie the postcaval 

 Vein just in front of the diaphragm and just back of the liver ; 

 cut away and remove the liver. 



10. Observe the two bean-shaped kidneys attached to the 

 dorsal wall of the abdomen. , They are covered by a thin layer 

 of membrane, the peritoneum, which lines the whole of the 

 abdominal cavity, and turns downward to form the mesentery, 

 which, like a sling, holds the intestine in place ; the mesentery 

 also covers, and almost completely surrounds, the stomach as 

 well as the liver. An artery, a branch of the aorta, extends into 

 each kidney, and from each kidney there runs a vein to join the 

 large postcaval vein. There is also a tube, the ureter, from 

 each kidney, running back to the urinary bladder. 



THE HEART AND LUNGS IN NATURAL POSITION. 



i . It should be noted that the heart and lungs collapse when 

 the chest is opened, and that they do not now show their natural 

 size. Slit the skin along the middle of the throat and find the 

 windpipe. Cut a slit in it lengthwise. Insert a tube, connected 

 by rubber tubing with a pair of bellows ; or inflate by the breath. 

 The lungs may be swelled to their natural size, filling the chest. 

 This will also show the natural relations of the heart and lungs. 

 Note how the lungs nearly surround the heart. Compare the 



