80 



COMPARATIVE ZOOLOGY. 



the nostrils, and two from 

 the ears; one from the 

 windpipe, guarded by 

 the epiglottis ; one from 

 the mouth, with a fleshy 

 curtain called the soft pal- 

 ate ; and one from the 

 cesopliagus. It is the nat- 

 ural passage for food be- 

 tween the mouth and the 

 oesophagus, and of air be- 

 tween the nostrils and 

 windpipe. Like the 

 month, it is lined with a 

 soft mucous membrane. 



The oesophagus is a 

 long and narrow tube, 

 formed of two muscular 

 layers: in the outer lay- 

 er, the fibres run length- 

 wise; in the other, they 

 are circular. It is lined 

 with mucous membrane. 

 While in all Fishes', 

 Reptiles, and Birds the 

 body cavity is one, in 

 Mammals it is divided, 

 by a partition called the 

 diaphragm, into two cav- 

 ities — the thorax, con- 

 taining the heart, lungs, 



Pio. M Dipestrve Apparatus of Mnn (diagram): 1,toiigne; 2, pharynx; 3, (Esopha- 

 gus ; 4, soft palate ; B, larynx ; C, palate ; 7, epiglottis ; 8, thyroid cartilage ; 9, 

 begitiniug of spinal marrow; 10, H, 12, vertebrre, with spinons processes; 13, 

 cardiac orifice of stomach; 14, left end of stomach ; 18, pyloric valve; 19, 20, 21, 

 dnodenom; 22, gall-hladder ; 2T, duct from pancreas ; 28, 20, jejunum ofintesiiue; 

 30, ileum ; 34, ccecnm ; 86, 37, 88, colon, or large intestine ; 40. rectum. 



