374 ELEMENTARY ZOOLOGY 



side of the paw. How does the hind foot of the mouse 

 differ from the foot of man ? Posteriorly the body is 

 terminated by a long tail. At the root of the tail is a 

 small aperture, the amis, and just below, or ventral to it, 

 is the opening from the kidneys and reproductive organs. 



TECHNICAL NOTE. Place the mouse on its back in a dissecting- 

 pan and cut through the skin from anus to the lower jaw. Extend 

 the legs, pin down each foot and pin out the cut edges of the 

 skin. Now carefully cut forward through the body-wajl from the 

 anal region and on through the breast-bones and ribs. Pin each 

 side out. 



Near the hindmost pair of ribs note a sheet of muscles, 

 the diaphragm, which extends across the body-cavity, 

 dividing it into an anterior portion, the thoracic cavity, 

 and a posterior, the abdominal cavity. What are the most 

 conspicuous organs in the thoracic cavity ? Leading 

 anteriorly to the mouth-cavity is a long tube, the trachea, 

 composed of a series of cartilaginous parts of rings placed 

 end to end. Note at its anterior end the glottis and 

 epiglottis. Insert a blowpipe into the glottis and inflate 

 the lungs, which will fill all the otherwise unfilled space 

 in the thoracic cavity. The abdominal cavity contains 

 the viscera suspended in a fold of the lining membrane, as 

 in the other vertebrates studied. Note lying against the 

 diaphragm a large, red, glandular structure, the liver. 

 Separate the two large lobes of the liver and expose the 

 opalescent gall-bladder. By passing a canula into this 

 and ligaturing, the cystic duct may be injected. Beneath 

 the liver is a large loop-shaped expansion of the alimen- 

 tary canal, the stomach. Arising from the right end of 

 the stomach is the narrow duodenum, which gradually 

 merges into the very much convoluted small intestine, or 

 ileum, which is followed by the large intestine, or colon, 

 the last part of which is a straight tube, the rectum. The 

 small intestine occupies most of the space in the peri- 



