22 HUMAN PHYSIOLOGY. 



and oils, furnishing the force which is transformed by the muscular system 

 into motor power. When employed exclusively as food for any length of 

 time, the albuminous substances are incapable of supporting life. 



The Saccharine principles are important to the process of nutrition, but 

 the changes which they undergo are not fully understood ; they form but a 

 small proportion of the animal tissues, and by oxidation generate heat and 

 force. Starch undergoes conversion into dextrin and grape sugar. 



The Oleaginous principles form a large part of the tissues of the body. 

 They are introduced into the system as food, and are formed also from a 

 transformation of albuminous matter during the nutritive process ; they 

 enter into the composition of nervous and muscular tissue, and are stored 

 up as adipose tissue in the visceral cavities and subcutaneous connective 

 tissue, thus giving roundness to the form and preventing, to some extent, 

 the radiation of heat. While they aid in the reconstruction of tissue, they 

 mainly undergo oxidation, giving rise to the production of heat and the 

 evolution of muscular and nervous force. 



The Inorganic principles constitute an essential part of all animal tissues, 

 and are introduced with the food. 



Water is present in all fluids and solids of the body, holding their 

 ingredients in solution, promoting the absorption of new material into the 

 blood and tissues, and the removal of waste ingredients. 



Sodium chloride is an essential constituent of all tissues, regulating the 

 passage of fluids through animal membranes (endosmosis and exosmosis). 



Calcium phosphate gives solidity to bones and teeth, constituting more 

 than one-half their substance. 



Iron is a constituent of the coloring matter of the blood. 



The Vegetable acids are important to nutrition, and tend to prevent the 

 scorbutic diathesis. 



The Accessory foods also influence the process of nutrition. Tea excites 

 the respiratory function, increasing the elimination of carbonic acid. Coffee 

 is a stimulant to the nervous system ; increases the force of the heart's 

 action, increases the arterial tension and retards waste. 



Alcohol, when introduced into the system in small quantities, undergoes 

 oxidation and contributes to the production of force, and is thus far a food. 

 It excites the gastric glands to increased secretion, improves the digestion, 

 accelerates the action of the heart and stimulates the activities of the 

 nervous* centres. In zymotic diseases, and all cases of depression of the 

 vital powers, it is most useful as a restorative agent. When taken in 

 excessive quantities, it is eliminated by the lungs and kidneys. The meta- 

 morphosis of the tissue is retarded, the elimination of urea and carbonic 



