CHORD ATA — VERTEBRATA 33 1 



untary muscles, all muscles moving the bones, for example, 

 are supplied with nerves from the brain or spinal cord. The 

 involuntary muscles, those in the walls of the blood vessels and 

 digestive canal, for example, are supplied with nerves from the 

 sympathetic nervous system. 



The interior of the trunk, called the body cavity, is divided 

 into two parts by a fiat partition-like muscle, the diaphragm, 

 attached to the backbone and ribs (Fig. 142, di.). The anterior 

 or thoracic cavity contains the heart and lungs ; the poste- 

 rior or abdominal cavity contains the stomach, intestine, liver 

 and kidneys. 



Digestion. — - In a wild state the food of the cat consists 

 principally of animals which it procures by means of its sharp 

 claws and sharp teeth. This is then partially crushed by the 

 teeth and at the same time preparatory to being swallowed is 

 thoroughly moistened by the saliva. Passing down the esoph- 

 agus the food enters the stomach, where the gastric juice dis- 

 solves the proteid constituents, thence to the small intestine, 

 where bile, poured in from the liver, emulsifies the fats, and the 

 pancreatic juice from the pancreas acts upon starches, proteids 

 and fats. The digested food is absorbed by the many blood- 

 vessels and lymphatics surrounding the digestive canal, espe- 

 cially the stomach and small intestine ; the undigested remnant 

 passes through the large intestine and out by the anus. 



As in most of the higher animals, both Invertebrata and 

 Vertebrata, the digestive canal is much coiled to give a greater 

 area for digestion and absorption ; in the cat it is five times the 

 length of the body exclusive of the tail. 



The cat has two sets of teeth ; the thirty of the second or per- 

 manent set begin to displace the twenty-six of the first set or 

 milk teeth at the end of the fourth month. In the adult cat 

 there are in the upper jaw, upon each side, three small cutting 

 teeth or incisors, one fang or canine, three premolars, and one 

 molar. The back premolar, very large and especially adapted 

 to cutting flesh, is called the sectorial tooth. In the lower jaw, 



