436 zooLoar 



stomach, where it is well churned and subjected to pepsin and 

 hydrochloric acid. Thence the food goes to the first part of the 

 small intestines (duodenum), where it is treated to the action 

 of the bile and the pancreatic juice. The food, now digested, 

 passes slowly down the long, small intestine, which is richly 

 supplied with l^anph and blood-vessels, into which the food 

 passes to be carried away to the tissues. Further absorption 

 takes place in the large intestine, and finally the unabsorbed 

 remains collect in the rectum. 



Organs of Circulation. — The circulation in general resembles 

 that of birds. The heart is divided into two separate halves, 

 each with its auricle and ventricle. The right auricle receives 

 a pair of large veins from the fore limbs and head and a single 

 vein coming from the posterior part of the body. The filood 

 thus collected in the right auricle passes to the right ventricle, 

 and thence is pmnped to the right and left lungs. From the 

 lungs it returns to the left auricle, to be pumped by the left 

 ventricle into the aorta. The aorta gives off arteries to the 

 fore limbs and head, and then passes on the left (instead of the 

 right, as in birds) of the gullet to form the dorsal artery, which 

 supplies the hinder part of the bodj' and the A-iscera. While the 

 blood from the tail, hind legs, germ glands, and kidneys goes 

 directly back to the heart, the blood from the food-canal flows 

 first to the liver to deliver its load of food there, and then passes 

 on to the right auricle. 



Organs of Respiration. — The air that enters through the 

 nostrils crosses the back of the mouth and enters into the upper 

 part of the windpipe or larjiix, through a slit that is guarded 

 from the entrance of food by a fold — the epiglottis. The 

 wall of the larynx contains certain large cartilages which sup- 

 port and control the vocal cords; these are represented in 



