LIME PHOSPHATE. 43 



assume new forms by their mutual reactions. In this way it is subser- 

 vient to all the phenomena of absorption, transudation, exhalation, and 

 even of chemical union and decomposition, which make up the internal 

 nutritive functions of the animal frame. 



After forming part of the animal solids and fluids, and playing its 

 part in the vital processes of the interior, the water is again discharged ; 

 for its presence in the body, like that of all the other proximate princi- 

 ples, is not permanent, but only temporary. It makes its exit from the 

 body by four different passages : namely, in a liquid form with the urine 

 and feces, and in the form of vapor by the lungs and skin. The actual 

 quantity which is expelled in each case is not uniform, but varies accord- 

 ing to circumstances. Thus, if the kidneys be unusually active, the 

 watery ingredients of the urine will be temporarily increased in quantity, 

 while the cutaneous perspiration will be diminished ; and the state of 

 the atmosphere and the rapidity of respiration will influence for the 

 time the amount of watery vapor exhaled by the lungs and skin. Still 

 there is a well-marked average relation between the functional activity 

 of the various organs and the daily quantity of their excreted fluids. It 

 appears from a comparison of the researches of Lavoisier and Seguin, 

 Valentin, and other observers, that the water which is thus discharged 

 from the system finds its way out by these different routes nearly in the 

 following proportions : 



By exhalation from the lungs 20 per cent. 



By the cutaneous perspiration . .... 30 " 

 By the urine and feces 50 " 



While only four per cent, of the water is expelled with the feces, 

 ninety-six per cent, passes out by the lungs, the skin, and the kidneys. 

 It is evident, therefore, that at least the main bulk of the water 

 taken in with the food does not simply pass through the alimentary 

 canal, but is taken up by the mucous membranes, enters the circulating 

 fluid, and forms a temporary constituent of the solid tissues of the 

 body. As it appears in the secretions it also brings with it various 

 ingredients which it has absorbed from the substance of the glandular 

 organs; and when finally discharged it is mingled in the urine and feces 

 with salts and excrementitious matters, which it holds in solution, and 

 in the cutaneous and pulmonary exhalations, with animal vapors and 

 odoriferous materials of various kinds. In the perspiration it also con- 

 tains mineral sulphates and chlorides, which it leaves behind on evapo- 

 ration. 



2. Lime Phosphate, Ca 3 P 4 8 . 



This substance exists as an ingredient of all the animal solids and 

 fluids without exception. So far as regards its mass, it is, next to 

 water, the most important of the inorganic constituents of the body, as 

 its entire quantity is far greater than that of any other of the mineral 

 salts. For, although it is not especially abundant in the fluids and 



