CHAP. II.] THE BLOOD. 67 



carbonate NaHC0 3 . The grounds for this supposition are (a) that 

 the plasma and serum contain considerable quantities of carbon 

 dioxide held partly in simple solution and partly in a state of feeble 

 combination as it is in sodium acid carbonate : (6) that when the 

 proteid matters are separated from the serum by adding to it a large 

 quantity of alcohol, and then solution of mercuric chloride is added, 

 there is produced a brown crystalline precipitate of oxychloride of 

 mercury (probably HgCl 2 , 4HgO), such as separates when mercuric 

 chloride is added to solutions of sodium acid carbonate. If the 

 sodium existed as normal sodium carbonate, a yellow precipitate of 

 HgO would be thrown down instead. (Liebig.) 



5. The ash of plasma and of serum contains about 4 per cent, of 

 potassium chloride which, there is every reason to believe, exists as 

 such in these fluids before they are subjected to chemical treatment. 



The great preponderance of salts of sodium as contrasted with 

 salts of potassium in the plasma and serum is one of the in- 

 controvertible and most interesting facts relating to the saline 

 constitution of these liquids. 



Salkowsky found, in two cases, in the serum obtained from the 

 blood of healthy men, that the ratio of potassium to the sum of 

 potassium and sodium in the ash was respectively as 13 9 : 100 

 and 10'4 : 100, and A. Schmidt found the proportion to be in two 

 cases 7'6 : 100 and 8'6 : 100. 



6. In addition to the inorganic constituents referred to, the ash of 

 plasma and serum is found to contain sulphuric and phosphoric acids and 

 magnesium and calcium ; and arranging the results of the analyses in 

 accordance with the rules followed in such cases it would result that 

 the serum contains ortho-phosphates of calcium, magnesium and 

 sodium, as well as a small quantity of potassium sulphate. 



We can, however, have no certainty from the results of such 

 analyses as to the constitution of phosphates existing in the unaltered 

 liquids. Admitting for instance that sodium compounds of orthophos- 

 phoric acid (H 3 PO 4 ) exist in the plasma and serum, analysis in no way 

 allows us to decide whether the compound present is the neutral tri- 

 sodium phosphate Na 3 P0 4 or the alkaline hydrogen di-sodium phos- 

 phate HNa 2 P0 4 or H 2 NaP0 4 , of which the second, for other reasons, 

 has been supposed to exist in the blood and probably actually does 

 so. Again, the serum contains appreciable quantities of lecithin 

 or some other derivative of glycerin-phosphoric acid. When that 

 body is ignited it leaves metaphosphoric acid,which reacting upon alka- 

 line and earthy carbonates would produce salts which in the analyses 

 would be reckoned as phosphates. The question therefore arises whether 

 the phosphoric acid which is found as a constituent of the ash really 

 exists as such in the liquor sanguinis or whether it is there present as 

 one of the products of the oxidation of such an organic body as lecithin. 



The observations of Pribram and Gerlach allow u-s to decide the 

 question. These observers have proved that calcium, magnesium 



52 



