34 



CLASSIFICATION 



solid or semi-solid fragments, hence the necessity for an internal 

 digestive cavity, the possession of which is characteristic of a 

 higher animal as contrasted with a higher plant. In Man, for 

 example, we have a set of digestive organs, the function of 

 which is to deal with this crude food and reduce it to such a 

 condition that it can be utilized for repair and growth, or, in 

 other words, to digest it. 



Digestive Organs. — These consist essentially of a long 

 digestive tube, more briefly termed the gut, into which a number 

 of structures known as digestive glands pour fluids. 



I. The Gut. — The gut (figs. 8 and 9) is of very unequal 

 width in different parts of its course, and, being very much longer 

 than the body, is only 

 able to pursue a straight 

 course from the mouth 



llhr- 



?'-. 



Fig. 8. — Section showing Mouth and Nasal 

 Cavities, Gullet, Windpipe, &c. 



u^ Hard palate ; ^ to », soft palate; c, mu- 

 cous membrane; n, cavity of nose; i, tongue; 

 ph, pharynx; g, gullet; ep, epiglottis; a/, 

 windpipe. 



Fig. 9.— The Gut 

 a. Gullet; 3c, stomach; def^ small intestine; remain- 

 ing letters indicate parts of large intestine. 



to the end of the thorax, while in the abdomen it is largely 

 coiled. The mouth, bounded by fleshy lips, leads into the fairly 

 large mouth-cavity, marked features of which are the teeth and 

 muscular tongue. At the back of this cavity is the pharynx, 

 communicating with the cavities of the nose and ear; while on 

 its floor is an opening, the glottis, leading into the breathing 

 organs. The pharynx may be looked upon as the dilated front 



