v THE BLOOD: PLASMA 125 



amount of haemoglobin diffuses out and stains the plasma. The 

 separation of the proteins of the blood in a pure state was, 

 however, effected by A. Schmidt and Hammarsten, mainly with 

 salted plasma. To-day we are acquainted with various less active 

 saline solutions, which when properly used do not rupture the 

 erythrocytes, and yield a perfectly colourless plasma ; among these 

 are sodium oxalate and metaphosphate. 



Lastly, it should be noted that plasma can be rendered in- 

 coagulable by adding sodium oxalate to the amount of 0'06-0'10 

 per cent to the fresh blood issuing from the vein. We shall 

 return to these facts in discussing the theory of coagulation. 



Still greater difficulties arise when we attempt not merely to 

 obtain more or less genuine plasma, but also to determine the 

 quantitative ratio between the normal mass of corpuscles and the 

 plasma. The methods employed with this object by Hoppe-Seyler 

 and Bunge give very different values, not only for different 

 animals, but also for different animals of the same species. With- 

 out citing the results of the various series of observations, we may 

 say that in man the amount of plasma is slightly in excess of 

 that of the corpuscles, in the wet state : average, 52 per cent 

 plasma and 48 per cent corpuscles (Arronet). In the horse, on 

 the contrary, the opposite result is obtained : average, 47 per cent 

 plasma and 53 per cent corpuscles (Bunge). 



II. According to recent analysis, blood plasma contains on an 

 average 91*8 per cent water and 8'2 per cent solid substances; 

 6'9 per cent of this consists of proteins, so that all the other 

 constituents of plasma are reduced to 1*3 per cent, of which about 

 0*46 per cent are organic extractives, 0'84 per cent inorganic. 



In all the higher animals the proteins of blood plasma consist 

 mainly of globulins (metaglobulin and paraglobulin), and to a 

 less degree of serum albumin. 



The most important is metaglobulin, commonly called fibrino- 

 gen, because it gives rise during coagulation to fibrin formation. 

 It is therefore entirely absent from serum, and to prepare it in a 

 pure state salted plasma must be used, or the morbid transudations 

 of the pericardium (hydropericardial fluid), or the tunica vaginalis 

 testis (hydrocele fluid), which always contain it. It can be separated 

 out from salted plasma by utilising the property which causes 

 fibrinogen to precipitate from its solutions so soon as these 

 contain 16 per cent of sodium chloride, when none of the other 

 globulins have lost their solubility, since they are precipitated 

 only when their solutions are saturated with sodium chloride. 

 To precipitate metaglobulin from the transudates, it is only 

 necessary to add sodium chloride in the solid form. 



If a solution of pure fibrinogen is warmed to 56-60 C., it 

 splits up into two other globulins, of which we shall speak later, 

 and an insoluble coagulum is formed. 



