PROXIMATE PRINCIPLES IN GENERAL. 37 



tion by the presence of other soluble substances. Thus, the insoluble 

 lime phosphate of the urine is held in solution by the acid reaction of 

 the sodium biphosphate, which is also present as an ingredient. In the 

 alkaline blood-plasma, on the other hand, the lime phosphate is lique- 

 fied by union with the albumen, which is itself soluble in the water of 

 the plasma. The same substance may be fluid in one part of the body, 

 and solid in another part. Thus in the blood and secretions the water 

 is fluid, and holds in solution other substances, both animal and mine- 

 ral, while in the, bones and cartilages it is solid not crystallized, as in 

 ice, but amorphous and solid, by the fact of its intimate union with the 

 animal and saline ingredients, which are abundant in quantity, and 

 which are themselves present in the solid form. Again, the lime phos- 

 phate of the blood is fluid by solution in the albumen; but in the bones 

 it forms a solid substance with the animal matter of the osseous tissue ; 

 and yet the union of the two is as intimate and homogeneous in the 

 bones as in the blood. A proximate principle, therefore, never exists 

 alone in any part of the body, but is always intimately associated with 

 a number of others, by a kind of homogeneous mixture or mutual solu- 

 tion. 



Every animal tissue and fluid contains a number of proximate prin- 

 ciples which are present, as we have already mentioned, in certain 

 characteristic proportions. Thus, water is present in very large quan- 

 tity in the perspiration and the saliva, but in very small quantity in 

 the bones and teeth. Sodium chloride is comparatively abundant in 

 the blood and deficient in the muscles. On the other hand, potassium 

 chloride is more abundant in the muscles, less so in the blood. But 

 these proportions are nowhere absolute or invariable. There is a great 

 difference, in this respect, between the chemical composition of an inor- 

 ganic substance and the physiological constitution of an animal fluid. 

 The former is always constant and definite ; the latter always presents 

 certain variations. Thus, water is always composed of exactly the 

 same relative quantities of hydrogen and oxygen ; and if these propor- 

 tions be altered in the least, it thereby ceases to be water, and is con- 

 verted into some other substance. But in the urine, the proportions 

 of water, urea, urates, phosphates, etc., vary within certain limits in 

 different individuals, and even in the same individual, from one hour 

 to another. This variation, which is almost constantly taking place, 

 within the limits of health, is presented by all the animal solids and 

 fluids. It is even a necessary accompaniment of the actions of life, and 

 one of the characteristic phenomena of living beings. For all parts of 

 the body are composed of different ingredients which are supplied by 

 absorption or formed in the interior, and which are constantly given 

 up again, under the same or different forms, to the surrounding media 

 by the unceasing activity of the vital processes. Every variation, then, 

 in the general condition of the body, as a whole, is accompanied by a 

 corresponding variation, more or less pronounced, in the constitution 

 of its different parts. This constitution is consequently of a very dif- 



