VERTEBEATA MAMMALIA. 



sets of teeth; the first, termed the milk or deciduous 

 teeth, being succeeded by the permanent teeth. Gen- 

 erally, there are four different sorts of teeth present 

 incisors, canines, praemolars, and 

 molars. The exceptions to this rule 

 are numerous, the number and varie- 

 ties of teeth present differing much 

 in the various "orders" into which 

 the class Mammalia is divided. 



The food during mastication is mixed 

 with a substance called saliva, secreted 

 by the salivary glands. These glands 

 are absent in the whales. It then 

 passes through a tube called the oeso- 

 phagus or gullet into the stomach, 

 where it is acted upon by a fluid termed 

 the gastric juice. By means of this 

 fluid it is converted into a substance 

 called chyme. This chyme passes 

 through the small intestine, where 

 it is acted upon by the bile, secreted 

 by the liver; and the pancreatic 

 juice, produced by another gland 

 called the pancreas. 



" The special function of the sali- 

 vary glands is to digest the starch 

 compounds of the food; and the special Fm< 6> _ HlND LlMB OP 

 function of the gastric juice is to di- ' A MAN. 

 gest the nitrogenous elements of the &, femur or thigh hone; 

 food; the remaining or fatty elements g^j. &"&' : 

 of food are, in like manner, digested, /, metatarsus; g, pha- 

 and prepared for assimilation by the 2" 

 pancreatic juice." (Dr. Haughton.) 



By these fluids the chyme is changed into a milky 

 substance termed chyle, which is conveyed to the blood- 

 vessels by a set of tubes called lacteals. 



The small intestine is followed by a wider tube termed 

 the large intestine, which is provided at the outer 



