Jo 



ZOOLOGY. 



secreting pores. Externally, it ;i mux-ular tunic 



intended to act on the contents of tin- tub.-. A S-TOUS mem- 

 brane, large and translucent like all serous membranes, invests 

 it externally in the abdomen, serving to fix it in its place, and 

 to facilitate its movements. 



43. The digestion of the food is effected mainly by the 

 action of different humours, which the food imbibes whilst 

 passing through the alimentary canal. These humours are 



Maxillary Gland. 

 Trachea. 



Colon 



Caecum 



Small Intestine 



Parotid Gland. 



..pharynx. 



Gullet. 



Thorax. 

 Aorta. 



$J|--- Midriff, 

 rjja .. Stomach . 

 5JSr Pancreas. 



9 Spleen. 



f Kidneys. 



- Colon. 



I Abdomen. 

 5 .Rectum. 

 -Bladder. 



Fig. 4. Digestive Apparatus of an A}--. 



chiefly the secretions from certain bodies, called glands, situ- 

 ated around the digestive tube, and destined to pour into its 

 cavity various liquids or secretions. The number of these 

 secreting organs varies in different animals, but generally 

 they are sufficiently numerous. The more important are the 

 salivary and gastric glands, the liver and the pancreas 



44. Finally, to facilitate the action of the digestive juices 



