CHAPTER VI 

 DIGESTION 



The Principal Processes of Nutrition The General Plan of Digestion 

 Mastication The Teeth Preservation of the Teeth Action of 

 the Saliva The Stomach and the Gastric Juice llie Movements of 

 the Stomach Gastric Digestion The Intestines The Bile and 

 Pancreatic Juice Intestinal Digestion Absorption by means of 

 Blood-vessels and Lacteals The Lymphatic or Absorbent System 

 The Lymph Conditions which affect Digestion The Quality, Quan- 

 tity, and Temperature of the Food The Influence of Exercise and 

 Sleep The Kidneys The Spleen Effect of Alchohol on Digestion, 

 the Liver, and Kidneys 



1. Nutrition. The great design of food is to give nutriment 

 or nourishment to the body. But this is not accomplished 

 directly, as the food must first pass through certain preparatory 

 changes, as follows : (1), Digestion, by which the food is reduced 

 to a soluble condition ; (2), Absorption, by which, when digested, 

 it is taken into the blood ; (3), Circulation, which carries the 

 enriched blood to the various parts of the system; and (4), 

 Assimilation, by which each tissue selects from the blood the 

 materials necessary for its support, y , 



2. By these four steps the sustaining power of food is gradu- 

 ally brought into exercise and -the vital machinery kept in 

 working order, somewhat after the manner of the steam-engine. 

 To operate the latter, the force imprisoned within the coal 

 and water is set free and converted into motion by the burning 

 of the fuel and the vaporization of the water. It will be seen, 

 however, when .we come to study these operations in the human 

 body, that they are conducted silently and harmoniously, with 

 marvellous delicacy and completeness, and without that friction, 

 and consequent loss of power, which attend the working of the 

 most perfect machinery of man's invention. 



1. Design of food ? How accomplished ? 



2. Sustaining power of food ? Simile of the engine ? Operation in the human body ? 



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