134 



DIGESTION. 



Fig. 28. 



solvent fluid is secreted. Then follows the intestinal canal with its 

 various divisions and variations. 



In the carnivora the alimentary canal is shorter and narrower than in 

 the preceding, and presents fewer complexities. The food upon which 



these animals subsist is softer 

 than that of the herbivora, and 

 less encumbered with indigest- 

 ible matter; so that the process 

 of its solution requires a less 

 extensive apparatus. 



In the human species, the 

 food is naturally of a mixed 

 character, containing both ani- 

 mal and vegetable substances. 

 But, notwithstanding this dif- 

 ference in the kind of nourish- 

 ment, the digestive apparatus 

 in man resembles closely that 

 of the carnivora. For the 

 vegetable matters which we 

 take as food are, in the first 

 place, artificially separated, to 

 a great extent, from indigesti- 

 ble impurities ; and secondly, 

 they are so softened by the 

 process of cooking as to be- 

 come nearly or quite as di- 

 gestible as animal substances. 

 In the human species the 

 process of digestion, though 

 simpler than in the herbivora, 

 is still somewhat complex. 

 The alimentary canal is di- 

 vided into different compart- 

 ments or cavities, which com- 

 municate with each other by 

 narrow orifices. At its com- 

 mencement (Fig. 28) we find 

 the cavity of the mouth, which 

 is guarded at its posterior ex- 

 tremity by the muscular valve 

 of the isthmus of the fauces. 

 Through the pharynx and 

 oesophagus (a), it communi- 

 cates with the second compart- 

 ment, or the stomach (6), a flask-shaped dilatation, guarded at its cardiac 

 and pyloric orifices by circular bands of muscular fibres. Then follows 



HUMAN ALIMENTARY CANAL. a. (Esoph- 

 agus, b. Stomach, c. Cardiac orifice, d. Pylorus. 

 e. Small intestine. /. Biliary duct. 0. Pancreatic 

 duct. h. Ascending colon, i. Transverse colon. 

 ;. Descending colon, k. Rectum. 



