14: ALIMENTATION. 



accumulate and induce serious toxic conditions. Examples 

 of this are found in those diseases of the kidneys which in- 

 terfere with the elimination of urea, producing ursemic poi- 

 soning, and in diseases of the liver which interfere with the 

 elimination of cholesterine, giving rise to cholestersemia. 



It is evident from the amount of matter which is daily 

 discharged from the body that the process of destructive 

 assimilation, as it is sometimes called, must be very active. 

 Its constant operation necessitates a constant appropriation 

 of new matter by the parts, in order that they may main- 

 tain their integrity of composition, and be always ready to 

 perform their functions in the economy. The blood con- 

 tains all the principles necessary for the regeneration of the 

 organism. Its inorganic constituents are generally found in 

 the same form in which they exist in the substance of the 

 tissues; but the organic principles of the parts are formed 

 in the substance of the tissues themselves by a transforma- 

 tion of material furnished by the blood. The physiological 

 decay of the organism is, therefore, being constantly re- 

 paired by the blood ; but in order to keep the great nutri- 

 tive fluid from becoming impoverished, the materials which 

 it is constantly losing must be supplied from some source 

 out of the body, and this necessitates the ingestion of matters 

 which are known as food. Food is taken into the body in 

 obedience to a want on the part of the system which is 

 expressed by the sensation of hunger, when it relates to 

 solid or semi-solid matters, and thirst, when it relates to 

 water. As these sensations are the first cause of the intro- 

 duction of the materials capable of regenerating the blood, 

 their consideration naturally precedes the study of digestion, 

 the process by which the articles of food are prepared for 

 absorption and appropriation by the circulating fluid. 



Hunger and Thirst. 



The term hunger may be applied to all degrees of that 

 peculiar want felt by the system which induces the ingestion 



