198 PHYSIOLOGY. 



Inorganic Constituents. The plasma's greatest factor is water. 

 It is this which gives it fluidity and is present to the extent of 90 

 per cent. There are present many salts; sodium chloride, carbonate 

 of soda, chloride of potassium, sulphate of potassium, phosphate of 

 calcium, phosphate of sodium, and phosphate of magnesium. The 

 first two occur in the greatest amounts, the remaining ones only 

 as traces. It is carbonate of soda that gives to plasma its ability to 

 absorb carbonic acid and it also contributes much to its alkalinity. 



Organic Constituents. These components are readily divisible 

 into proteid and nonproteid groups. 



THE PKOTEIDS are: 



1. One albumin (serum-albumin). 



2. Two globulins, termed serum-globulin and fibrinogen. 



3. A nucleo-proteid. 



In Weight. In Volume. 



Fig. 60. Relative Proportion of Corpuscles and of Plasma. (Human 

 Blood. ) ( LANGLOIS. ) 



The classes of proteids present various solubilities in neutral salt 

 solutions, by appreciation of which they are able to be separated 

 from one another. 



The albumins upon half-saturation with ammonium sulphate 

 remain in solution, while the globulins and nucleo-proteids are pre- 

 cipitated. The precipitate is removed by filtrations, or the albu- 

 mins may themselves be precipitated by saturation with ammonium 

 sulphate. 



The globulins almost universally possess the characteristic of 

 coagulating when heat of 75 C. is applied to them. In man the 

 globulins make up about 3 per cent, of the total serum. 



Fibrinogen is also a globulin. It is precipitated by half -satura- 

 tion with NaGl thus making its differentiation from serum-globulin 

 a comparatively easy task. Upon precipitating with NaCl, if a lime 

 salt be added, the precipitate partakes of the nature of a fibrin-clot 



