86 
COMPARATIVE ZOOLOGY. 
the nostrils, and two from 
the ears; one from the 
windpipe, guarded by 
the epiglottis; one from 
the mouth, w T ith a fleshy 
curtain called the softpal¬ 
ate ; and one from the 
oesophagus. 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 
mouth, 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 Fish es, 
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, 
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, vertebrse, 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 intestiue; 
30, ileum; 34, coecum; 36, 37, 38, colon, or large intestine; 40. rectum. 
