BLOOD. 151 



The plasma of the blood contains salts, some of which are pe- 

 culiar to that fluid, and are transmitted from thence into the se- 

 cretions and excretions, while others (especially the phosphates of 

 lime and magnesia, fluoride of calcium, together with small quan- 

 tities of the sulphates and carbonates of soda and lime), occur in 

 the bones as actual constituents of the body. The latter are con- 

 veyed into the body with the food, partly in the state of phos- 

 phates, &c., while their formation is also in part due to the pro- 

 duction of phosphoric and sulphuric acids by exhalation of the 

 phosphorus and sulphur which occur in the protein-compounds, 

 and the subsequent combination of those acids with bases. 

 These salts are again found in the urine, for they are removed 

 by the blood during the metamorphosis of the bones, and are 

 excreted by the kidneys. In the present state of our chemical 

 knowledge, it is impossible to assign with certainty any de- 

 finite function, to the large quantity of salts, which enters the 

 blood but is not transferred into any of the solid textures of 

 the body. Hewson suggested that the object of the saline con- 

 stituents of the serum was to enable the blood-corpuscles to 

 retain their discoid form. Albumen, without salts, has as little 

 power as pure water in hindering the solution of the blood- 

 corpuscles. Hewson's view seems to be supported by the facts, 

 that the alkaline salts which occur in only a very slight pro- 

 portion in solid textui'es, are found in a very large quantity in 

 the blood ; and further, that when water is mixed with blood, 

 by injection into a vein, in a sufficiently large quantity to dis- 

 solve or modify the form of the corpuscles, a fatal result ensues. 

 As these salts are continuously introduced into the blood with 

 the food, a corresponding amount must be removed by the ex- 

 cretions. The salts have, however, other functions than that 

 assigned to them by Hewson. The blood, as is well known, 

 has always an alkaline reaction, and it might therefore be sup- 

 posed that if a large quantity of an acid were taken, the reaction 

 of the blood would be neutralized. This is, however, by no 

 means the case, partly because only a certain quantity of the 

 acid enters the blood, the remainder being carried off by the 

 intestinal canal, and partly because the portion that does enter 

 the circulating fluid is at once removed by the kidneys. Thus 

 all the mineral acids may be detected in the urine after their 

 administration ; the vegetable acids appeal*, however, to undergo 



