INORGANIC SUBSTANCES. 157 



is a clear yellowish liquid of alkaline reaction and sp. gr. about 1027-1031. 

 It contains about 90 per cent, of water, holding various organic and 

 inorganic substances in solution. With the exception of certain proteids, 

 the constituents of plasma are identical with those of serum, in which 

 they are more readily studied. 



Inorganic substances. Plasma consists to about 90 per cent, of 

 water. The inorganic salts occur to the amount of about 0'8 per cent. 

 The principal is chloride of sodium. This can be crystallised out from 

 plasma after inspissation. According to the analyses of C. Schmidt, it 

 is present to the extent of 0'55 per cent. Carbonate of soda is probably 

 the next most abundant salt, although its exact amount cannot be stated. 

 It is to this salt that plasma mainly owes its alkalinity and its power of 

 absorbing carbonic acid. Although it is not possible to state definitely 

 in what manner the acids and bases of the plasma are distributed, it 

 appears probable that, besides these two salts, chloride of potassium, 

 sulphate of potassium, phosphate of calcium, phosphate of sodium, and 

 phosphate of magnesium, and probably chloride of calcium, occur l in 

 small amounts. Traces of a fluoride have also been found. 2 



Gases. The gases of plasma have not been satisfactorily investi- 

 gated. They are probably not very different from those of serum, 

 which in the dog consist of from 43 to 57 vols. of carbonic anhydride, 

 2 -2 5 of nitrogen, and 0*25 of oxygen. 3 The oxygen and nitrogen are 

 probably simply dissolved in the plasma, but the carbonic anhydride 

 is present in far too great an amount for this to be the case, since 

 not more than 2 or 3 vols. per cent, of this gas could be dissolved. The 

 remaining amount must therefore be in chemical combination. This can 

 only be with soda, as carbonate and bicarbonate ; for other bases are 

 present in too small amount in plasma to be taken into serious considera- 

 tion. This statement is also true for alkaline phosphates, although in 

 the corpuscles, in which they are present in considerable quantity, they 

 may play an important part in fixing C0 2 (Bunge), as shown by the 

 following equation : 



Na 2 HP0 4 + H 3 C0 3 - H 2 P0 4 + NaHC0 3 . 



Some of the CO 2 may be combined with proteid, 4 but this can only be 

 very little. As a matter of fact, Bunge calculates that, after allowing 

 for the amount of soda required to saturate the only strong mineral acid 

 of the plasma (hydrochloric), there is enough left to fix 63 vols. per cent, 

 of C0 2 as carbonate, and an equal additional amount as bicarbonate, 

 which is far more than the amount of C0 2 actually present. 5 



Organic constituents of blood plasma. The organic constituents 

 of plasma may be divided into proteids and non-proteids, and the latter 

 into nitrogenous and non-nitrogenous. 



Non-nitrogenous organic substances found in plasma. These 

 consist of carbohydrates and fats; and, in addition, there are present 

 small quantities of a lipochrome, of cholesterin, and probably of sarco- 

 lactic acid. 



Carbohydrates of plasma. Three carbohydrates have been described 



1 Pribram, Abhandl. d. math.-phys. CL d. Tc. Sachs. Gesellsch. d. Wissensch., Math. -phys. 

 Klasse, 1871, Bd. xxiii. S. 279 ; and in Arb. a. d, physiol. Aiist. zu Leipzig, 1871, p. 63. 



2 Tamtnann, Ztschr. f. physiol. Chem., Strassburg, 1888, Bd. xii. S. 325. 



3 Bunge, op. cit., S. 286. 



4 Sertoli, Hoppe- Seyler s Mcd. Chem. Untersuch., Berlin, 1868, Heft 3, S. 350, 



5 Op. cit., S. 286. 



