48 IMMEDIATE PEINCIPLES OF THE TISSUES. 



the carbonic acid of the carbonates is set free by too elevated a tem- 

 perature, and then merely the base remains in the ashes. Salts enter 

 into the composition of every organized tissue, though sometimes 

 in the slightest degree. 



The salts in the fluids and tissues are merely dissolved in water; 

 on being dissolved, they then serve as solvents for other immediate 

 principles e. g. solutions of salts with alkaline bases (soda and 

 potassa) in the serum of the blood, dissolve certain fatty principles 

 there. 



None of the salts combine with the principles of the second class 

 (those formed by dis-assimilation) except common salt, which unites 

 with urea, forming the chloro-sodate of urea. It is, indeed, in this 

 combination with soda that urea exists in the blood, in the vitreous 

 humor of the eye, and, in part, also, in the urine. (B. and V.) 



Some of the salts, especially several of the phosphates, in con- 

 nection with water, combine directly with some of the organic sub- 

 stances (third class), and thus result certain organized substances, 

 or tissues. E. g. the phosphate of lime combines directly with the 

 osteine in bone, to form the tissue of the latter. 



Besides, the earthy salts especially, by their union with the or- 

 ganic substances, manifest a power in aid of assimilation; and 

 common salt, the phosphates of lime and magnesia, and the neutral 

 phosphate of soda, are found in every tissue and every fluid in the 

 body. Hence the salts are indispensable in our food. They also 

 aid in dis-assimilation by yielding their bases, while still forming a 

 part of the tissues, to acids of organic origin, as the uric and hip- 

 puric. By these latter combinations, also, the animal heat is in part 

 produced. Moreover, their presence with the principles of the 

 second class alone enables several of the latter to combine with 

 oxygen, and even to displace it from metallic oxides. 



Liebig discovered, in respect to this class, that the phosphates and 

 carbonates of soda may replace each other in the blood without 

 detriment. Hence, if the food contains only phosphates, without 

 carbonates e. g. bread and meat the blood contains no carbonates; 

 if potatoes be added to the preceding, the blood contains some car- 

 bonates; and if the diet be of fruits alone, the blood acquires the 

 character and the composition of that of the ox or sheep. The 

 urine also contains alkaline phosphates in the first case, and alka- 

 line carbonates in the latter. 



The observations of Bence Jones, to the effect that, in chorea and 



