66 PROXIMATE PRINCIPLES IN GENERAL. 



with the water. The same substance may be fluid in one part of 

 the body, and solid in another part. Thus in the blood and secre- 

 tions the water is fluid, and holds in solution other substances, both 

 animal and mineral, while in the bones and cartilages it is solid 

 not crystallized, as in the case of ice or of saline substances which 

 contain water of crystallization, 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 phosphate of lime in 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 

 solution. 



Every animal tissue and fluid contains a number of proximate 

 principles which are present, as we have already mentioned, in 

 certain characteristic proportions. Thus, water is present in very 

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

 quantity in the bones and teeth. Chloride of sodium is compara- 

 tively abundant in the blood and deficient in the muscles. On the 

 other hand, chloride of potassium is more abundant in the muscles, 

 less so in the blood. But these proportions, it is important to ob- 

 serve, are nowhere absolute or invariable. There is a great differ- 

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

 ganic substance and the anatomical constitution of an animal fluid. 

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

 subject to certain variations. Thus, water is always composed of 

 exactly the same relative quantities of oxygen and hydrogen ; and 

 if these proportions be altered in the least, it thereby ceases to be 

 water, and is converted into some other substance. But in the 

 urine, the proportions of water, urea, urate of soda, phosphates, 

 &c., 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 characteristic of all the animal solids and fluids ; for they 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, 



