in THE PROTEINS OF PLASMA 107 



their constituents, and that constituent is, as we have said 

 previousl)', the hgemoglobin ; for appropriate solutions of 

 hsemoglobin behave towards oxygen almost exactly as blood 

 does. Similarly the blood contains more carbonic acid than 

 could be held in solution by pure water at the same tem- 

 perature and pressure. But unlike the oxygen, the 

 carbonic acid thus held by blood is not peculiarly associated 

 with the h;emogloljin of the red corpuscles ; in fact it 

 seems to be chiefly retained by some constituents of the 

 plasma. 



The corpuscles differ chemically from the plasma, in 

 contaming a large proportion of the fats and phosphates, 

 all the iron, and almost all the potassium, of the blood ; 

 while the plasma, on the other hand, contains by far the 

 greater part of the chlorme and the sodium. 



The blood of adults contains a larger proportion of 

 solid constituents than that of children, and that of men 

 more than that of women ; but the difference of sex is 

 hardly at all exhibited by persons of flabby, or what is 

 called Ij-mphatic, constitution. 



Animal diet tends to increase the quantity of the red 

 corpuscles ; a vegetable diet and abstinence to diminish 

 them. Bleeding exercises the same influence in a still 

 more marked degree, the quantity of red corpuscles being 

 diminished thereby in a much greater proportion than 

 that of the other solid constituents of the blood. 



8. The Proteins of Plasma.— By cooling or the 

 addition of certain neutral salts the clotting of blood is 

 retarded or even entirely prevented. The corpuscles may 

 now be removed and the plasma obtained as a clear 

 faintly yellow and slightly alkaline liquid composed of 

 about 90 per cent, water and 10 per cent, of solids in 

 solution. The solids consist chiefly of that kind of 

 material which we have so frequently spoken of as protein. 

 Since these proteins are typical of their class, and since 

 proteins are without doubt the most important substances 

 met with in the body, it will be as well to state at once 

 what are the essential characteristics of a protein. 



