484 PHYSIOLOGY. 



The mineral salts are cast off in smaller amounts when no salts 

 are ingested, but they are never entirely absent. . With .organic food 

 materials the amount of salts excreted is minimal. 



Oxygen. We take in about 700 grams of oxygen, which is neces- 

 sary to oxidize the foods. 



Water. Bread contains 34 per cent, of water; meat 55 to 75 

 per cent, of water. 



Among the inorganic compounds, the most important, without 

 exception, is water. It is even more important than proteid and fat, 

 since it forms about three-fifths of the weight of the body. 



Water has an important function within the organism. When 

 proteid is insufficient, water accumulates in the tissues. Among the 

 poorer classes, whose nourishment is insufficient, infectious diseases 

 flourish, since their nutritive liquids are excellent media for the 

 cultivation of micro-organisms. 



Excess of water causes an augmentation of urea ; hence the success 

 of mineral waters in Bright's disease. This increase of urea is due to 

 the abundant washing out of the retarded metabolic acts through the 

 kidneys. 



Atwater and Benedict found in repose the amount of water taken 

 in on an average to be 2,290 cubic centimeters, on working days 3,700 

 cubic centimeters. In addition the body has water manufactured in it 

 by the oxidation of hydrogen in the food. The oxidation water amounts 

 to about 360 grams in a mixed diet, representing 3,000 calories. 

 Water is excreted only in relatively small amount by the faeces, 60 to 

 120 grams daily. Atwater and Benedict state that an average of 

 931 grams of water is given off by the skin and lungs during a day, 

 of which 531 grams come from the skin and 400 grams from the 

 lungs. Work greatly increases the evaporation from the ,skin. The 

 evaporation of water from the body is least in temperate climates, 

 greater at low temperature and much increased by high temperature. 

 The body loses less water in damp than in dry air. A strong sunlight 

 increases the evaporation of water. 



Increase of adipose tissue diminishes the water lost at low tempera- 

 ture, but greatly increases it at a high temperature. The ingestion 

 of water in repose increases the amount of urine, but leaves the 

 evaporation unchanged. Alcohol when taken in considerable quan- 

 tities increases the sweat excretion, due to the vasodilation in the skin. 

 The evaporation of a liter of water takes away from :the body 580 

 calories. Atwater and Benedict set down the heat lost by evaporation 

 during repose at 24.5 of the total. In a man with congenital defect 



