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 sof t pal- 

 ate ; and one from the 

 oesophagus. It is the nat- 

 ural passage for food be- 

 tween the mouth and the 

 oesophagus, arid of air be- 

 tween the nostrils and 

 windpipe. Like the 

 mouth, it is lined with a 

 soft mucous membrane. 



The oesophagus is a 

 long and narrow tube, 

 formed of two muscular 

 layers : in the outside one, 

 the fibres run length- 

 wise ; in the other, they 

 are circular. It is lined 

 with mucous membrane. 

 While in all Fishes, Rep- 

 tiles, and Birds the ven- 

 tral chamber is one, in 

 Mammals it is divided, 

 by a partition called the 

 diaphragm, into two cav- 

 ities the thorax, con- 

 taining the heart, lungs, 



PIG. 51. Digestive Apparatus of Man (diagram): 1, tongue; 2, pharynx; 3, oesopha- 

 gus; 4, soft palate; 5, larynx; 6, palate; 7, epiglottis; 8, thyroid cartilage; 9, 

 beginning of spinal marrow; 10, 11, 12, vertebra, with spinous processes; 13, 

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

 duodenum; 22, gall-bladder ; 27, duct from pancreas; 28, 29, jejunum of intestine; 

 30. ileum ; 34, coecum : 36, 37, 38, colon, or large intestine ; 40. rectum. 



