A treatise on physiology and hygiene for educational institutions and general readers .. . e gullet to the stomach (a re-ceptacle in which the principal work ofdigestion is performed), and thence on-ward through the small and large intes-tines. 4. The stomach and intestines aresituated in the cavity of the abdomen(Fig. 20, C, and Fig. 26), and occupyabout two-thirds of its space. The ac-tion to which the food is subjected inthese organs is of two kinds—mechani-cal and chemical. By the former it issoftened, agitated, and carried onwardfrom one point to another; by the lat-ter it is changed in f
A treatise on physiology and hygiene for educational institutions and general readers .. . e gullet to the stomach (a re-ceptacle in which the principal work ofdigestion is performed), and thence on-ward through the small and large intes-tines. 4. The stomach and intestines aresituated in the cavity of the abdomen(Fig. 20, C, and Fig. 26), and occupyabout two-thirds of its space. The ac-tion to which the food is subjected inthese organs is of two kinds—mechani-cal and chemical. By the former it issoftened, agitated, and carried onwardfrom one point to another; by the lat-ter it is changed in form through thesolvent power of the various digestivefluids. 5. Mastication.—As soon as solid food is taken into the mouth, it undergoes mastication or is caught between the opposite surfaces of the teeth, and by themis cut and crushed into very small fragments. In the movementsof chewing, the lower jaw plays the chief part; the upper jaw, hav-ing almost no motion, acts simply as a point of resistance, to meetthe action of the former. These movements of the lower jaw are. Fig. 20.—Section of the Trunk,showing the cavities of theChest and Abdomen. 8. Change of food in digestion ? Process of digestion ? Describe the alimentary canal. 4. Situation of the stomach and intestines? Action of the food? Mechanical action?Chemical ? 5. Describe the process of mastication. How many and what movements ? 106 DIGESTION. of three sorts: an up-and-down or cutting, a lateral or grinding, anda to-and-fro or gnawing motion. 6. The teeth are composed of a bone-like material, and are heldin place by roots running deeply into the jaw. The exposed por-tion, or crown, is protected bya thin layer of enamel (Fig. 21, a),the hardest substance in the body,and, like flint, is capable of strik-ing fire with steel. In the interiorof each tooth is a cavity, contain-ing blood-vessels and a nerve,which enter it through a minuteopening at the point of the root(Fig. 23). 7. There are two sets of
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Keywords: ., bookcentury1800, bookdecade1, booksubjectphysiology, bookyear1887
