26 PHYSIOLOGY. 



The inorganic compounds are water; the various acids, such as 

 the hydrochloric acid of the gastric juice; and numerous salts. 



Since the proximate principles of both food and the body are 

 the same, mention of the principles will be known to refer to both. 

 A very convenient method of grouping the principles of both food and 

 the body is that by Halliburton, as follow? : 



J Water. 

 ' I Salts, as chlorides and phosphates of sodium and calcium. 



{Proteids: albumin, myosin, etc. 

 Albuminoids: gelatin, keratin, etc. 

 Simpler nitrogenous bodies: lecithin, urea, etc. 

 ( Fats: butter, adipose tissue. 

 Nonnitrogenous < Carbohydrates: sugar, starch. 



(^ Simple organic bodies: alcohol, lactic acid. 



Although all of these elements are present, yet not all are of 

 equal importance or occur in the same proportions. Among the inor- 

 ganic group, water and salts are prominent; among the organic, car- 

 bohydrates, fats, and proteids. 



WATER. 



Water forms more than one-half of. the body-weight. The value 

 of water to the economy can be readily appreciated by the student 

 when he considers that the various processes and stages of digestion, 

 absorption, and assimilation are dependent upon hydration and dehy- 

 dration. About fifty ounces of urine are excreted daily, this being 

 the main avenue for the escape of watery elements from the body. 

 In addition, considerable water is given off by the skin as sensible 

 and insensible perspiration, while expired air is heavily laden with 

 moisture. 



With so much water making its escape from the body, at least 

 as much must find its way into the economy. About two and a half 

 quarts of water are ingested daily as food. The water we drink ought 

 to be fresh, limpid, without smell, and of an agreeable taste. When 

 complete and exact analysis is impossible, the taste is the only safe 

 criterion or judge as to its fitness. Drinking-water should always 

 contain a certain percentage of air. The palatability is due to the 

 presence of carbonic acid gas in the water. Besides gaseous constitu- 

 ents, solid substances are also present. These are both mineral and 

 organic, and should be present in but very small amount. 



