20 



ZOOLOGY. 



plexity is, that vegetable food, being less easy of digestion, 

 requires a longer sojourn in the stomachal cavities.* 



42. A membrane, called mucous, lines the digestive cavity 

 throughout. It is analogous to the skin, with which it is 

 continuous, hut differs in structure. It is much softer, and 

 in place of an epidermis is protected on its exposed surface by 

 a reticular tissue, soft and turgid, called epithelium. 



Maxillary Gland. 

 Trachea. ^ *,.. 



Liver...... 



Gall Bladder..^* 



Colon.-... 



Caecum. ,. % 



Small Intestine. .. 



Parotid Gland. 



Pharynx. 

 Gullet. 



Thorax. 

 Aorta. 



-Midriff. 



Stomach. 



Pancreas. 



Spleen. 



Kidneys. 



Colon. 



Abdomen. 



Rectum. 

 Bladder. 



Fig. o. Digestive Apparatus of an Ape. 



Finally, it is more vascular than the other, and abounds with 

 secreting pores. Externally, it possesses a muscular tunic 

 intended to act on the contents of the tube. A serous mem- 

 brane, large and translucent like all serous membranes, invests 



* The stomach is probably single in all animals, being simply subdivided in 

 some into different compartments. In whales, though strictly carnivorous 

 animals, the stomach is extremely complex. K. K. 



