492 NUTRITION. 



Origin and Discharge of Water. It is evident that a great proportion of the water in 

 the organism 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 hydro- 

 carbons and their combustion have led to the supposition 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 then to compare this quan- 

 tity 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, temperature, the state of the atmosphere, etc., and even if constant they 

 could be estimated with great difficulty. Experiments upon this point have been under- 

 taken 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, 

 faeces, lungs, and skin. There is no direct evidence that water is produced de now in the 

 interior of the body. In the issue of water by the kidneys and skin, it has long been 

 observed that, in point of activity, these two emunctories bear a certain relation to each 

 other. When the skin is inactive, as in cold weather, the kidneys discharge a large quan- 

 tity of water ; and, when the skin is active, the quantity of water discharged by the kid- 

 neys is diminished. Certain therapeutical agents, also, can be made to act as diapho- 

 retics, by combining other measures which favor cutaneous action, or as diuretics, by 

 employing measures to diminish the action of the skin. 



Chloride of Sodium. Chloride of sodium is next in importance, as an inorganic 

 proximate principle, to water. It is found in the body at all periods of life, existing, like 

 water, in the ovum. It exists in all the fluids and solids of the body, with the single 

 exception of the enamel of the teeth. In the fluids, it seems to be simply in a state of 

 solution, and it can be recognized by the ordinary tests. In this respect we may class 

 together the chlorides of sodium and potassium. 



The quantity of chloride of sodium in the entire body has never been estimated ; nor, 

 indeed, has any accurate estimate been made of the quantity contained in the various 

 tissues, for all the chlorides are generally estimated together. It exists in greatest pro- 

 portion in the fluids, giving to some of them, as the tears and perspiration, a distinctly 

 saline taste. The following table gives an idea of the quantities which have been found 

 in some of the most important of the fluids and solids : 



Table of Quantities of Chloride of Sodium. 



Parts per 1,000. 



In Blood, human (Lehmann) 4*210 



" Chyle (Lehmann) 5*310 



" Lymph (Nasse) 4-120 



" Milk, human (Lehmann) 0-870 



" Saliva, human (Lehmann) 1-530 



" Perspiration, human (mean of three analyses, Piutti) 3 '433 



" Urine (maximum) } C 7-280 



" (mean) > Valentin. < 4'610 



" (minimum) ) ( 2'400 



" Faecal matters (Berzelius) 3-010 



Function of Chloride of Sodium. The function of this principle is undoubtedly im- 

 portant, but it is not yet fully understood. It does not seem to enter into the substance 

 of the organized solids and semisolids as an important and essential element, but apparent- 



