222 COMPARATIVE MORPHOLOGY OF VERTEBRATES. 
PHARYNX. 
The pharynx is the division of the alimentary canal intervening 
between the cavity of the mouth and the cesophagus and is characterized 
by being at once alimentary and respiratory. From its walls are devel- 
oped the gill clefts and lungs as well as a number of derivatives of 
these, and it also receives the internal openings of the nasal passages. 
Hence it is best described in connection with the respiratory system. 
Fic. 226.—Salivary glands of fruit bat, Pteropus conspicillatus (Princeton, 2065). 
, pd, parotid gland and duct; 7/, rid, retrolingual gland and duct; sm, smd, submaxillary 
gland and duct. 
THE CSOPHAGUS. 
That part of the digestive tract between the pharynx and the 
entrance of the bile duct (fig. 209) develops into cesophagus, stomach 
and that part of the intestine known as the duodenum. Stomach and 
duodenum are separated by the pyloric valve described below, but it 
is difficult to draw a clear line between cesophagus and stomach. In 
general it may be said that the cesophagus is the tract immediately 
succeeding the pharynx, lying in front of the body cavity and thus 
lacking a serous coat; that it is smaller than the stomach, and that 
there are no digestive glands in its walls; but all of these statements 
have exceptions. 
