THE CHEMISTRY OF THE BODY 79 



The fats and oils are sometimes called hydro-carbons. They 

 consist of carbon, hydrogen, and oxygen, but the proportion of 

 oxygen is small. 



The amyloids (Gr. amulon, starch, and eidos, form) include 

 those compounds which resemble starch in chemical composition. 

 They contain the same three elements that form fats and oils, but 

 the proportion of oxygen is larger. In these compounds hydrogen 

 and oxygen are present in the same proportion in which they com- 

 bine to form water. The chief amyloids in the body are glycogen, 

 glucose or grape-sugar, and lactose or milk-sugar, 



The nitrogenous compounds are generally classified into 

 proteids or albuminoids and gelatinoids. 



The albuminoids include all those compounds which resemble 

 albumen or white of egg in composition. They are found in all 

 the living tissues of the body, and consist of carbon, hydrogen, 

 oxygen, and nitrogen, together with a small proportion of sulphur 

 or phosphorus. The chief albuminoids of the body are 



Albumen, found in the blood and most tissues. 



Globulin, found in the blood and many of the tissues. 



Myosin, found principally in muscles. 



Fibrin, formed in blood as it coagulates or clots. 



Casein, found in the milk. 



The gelatinoids are those compounds which resemble gela- 

 tine. The chief are : 



Gelatine, formed by boiling bone. 



Chondrin, found in cartilage. 



The inorganic or mineral compounds found in the body are 

 derived from our food and drink. Many of these pass through 

 the body without undergoing any change, but others form a 

 necessary part of the structure of certain tissues. Thus, the bones 

 are rendered firm and hard by the presence of certain mineral 

 compounds. The chief inorganic compounds are water, calcium 

 carbonate, calcium phosphate, and common salt. 



Although water is present largely in all living animal and vege- 

 table substances, yet it is regarded as an inorganic or mineral com- 

 pound More than two-thirds of the weight of the body is water. This 

 is derived chiefly from our food and drink, but a small quantity 

 is formed in the body. The uses of water in the body are 



1. To render the tissues soft, elastic, and flexible. This may 

 be easily illustrated by heating a tissue till all the water has been 

 driven off, when it will become hard, horny, and brittle. 



2. To dissolve nutrient matter, and convey it to all parts of the 

 body 'in a fluid form. 



3. To assist the various processes of absorption, secretion, and 

 excretion. 



