34 INTRODUCTION. 



Function of Water. After what has been stated re- 

 specting the condition in which water exists in the body, 

 there remains but little to say concerning its function. As 

 a constituent of organized tissues, it gives to cartilage its 

 elasticity, to tendons their pliability and toughness ; it is 

 necessary to the peculiar power of resistance of the bones, 

 and, as we have already seen, it is necessary to the proper 

 consistence of all parts of the body. It has other important 

 functions as a solvent. Soluble articles of food are intro- 

 duced in solution in water. The excreinentitious matters, 

 which are generally soluble in water, are dissolved by it in 

 the blood, carried to the organs of excretion, and discharged 

 in a watery solution from the body. 



Origin and Discharge of Water. It is evident that the 

 great proportion of water is introduced from without in the 

 fluids, and in the watery constituents of all kinds of food ; 

 but the theoretical views of some physiologists with regard 

 to the hydrocarbons and their combustion, led to the supposi- 

 tion that water is also formed in the body by a direct union 

 of oxygen and hydrogen. The true way of determining this 

 point is to estimate all the water introduced into the organism, 

 and compare this quantity with that which is discharged. The 

 latter estimate, however, presents very great difficulties. As 

 water is continually given off in the form of vapor from the 

 skin, and in the expired air, the quantities thus discharged 

 are subject to great variations, dependent upon exercise, tem- 

 perature, the state of the atmosphere, etc., and even if con- 

 stant could be estimated with great difficulty. Experiments 

 on this point have been undertaken by Sanctorius, Barral, 

 Boussingault, and others; but they are not sufficiently com- 

 plete to settle the question. 



In the present state of our knowledge, we can only say 

 that water is introduced with the fluid and solid elements of 

 food, by the stomach, and that it escapes by the urine, feces, 

 lungs, and skin. There is no direct evidence that any is pro- 



