RED BLOOD-CORPUSCLES. 83 



and this coagulating, forms a buffy coat, as before des- 

 cribed, the volume of which is augmented by the white 

 corpuscles, which have no tendency to adhere to the red 

 ones, and by their lightness float up clear of them. 



Chemical Composition of Red Blood-cells. 



The cell-wall is composed, doubtless, of a protein 

 material, but from the difficulty in isolating it from the 

 cell-contents, its composition cannot be accurately deter- 

 mined. The cruor, which is soluble in water, is com- 

 posed of two substances, intimately and perhaps chemically 

 combined, which have been named globulin and cru- 

 orin. The former, which preponderates in quantity over 

 the cruorin in about the proportion of 90 to 10, is colour- 

 less, and, in its nature and composition closely allied to 

 albumen and casein. It has been found in various 

 structures besides the red blood-cells, and exists in espe- 

 cially large quantity in the crystalline lens ; the globulin 

 from this source, however, differs from blood-globulin in 

 not being crystallizable. When separated from cruorin it 

 is almost insoluble in water, but can be dissolved by the 

 addition of a small quantity either of an acid or alkali. 

 It is precipitated from either solution, acid or alkaline, 

 on neutralization, and in either case can be again dissolved 

 by a slight excess. Heat throws it down from neither of 

 these solutions, although the same means will precipitate 

 it from a solution in neutral salts, not as a curd, but in 

 the form of fine molecules and granules. Carbonic acid 

 passed through its alkaline solution will precipitate it. 

 while it is re-dissolved by the passage of a stream of 

 atmospheric air or oxygen. 



The other constituent of the cruor, namely, the sub- 

 stance which gives the blood its red colour, has probably 

 not been separated in a pure and unaltered state. The 

 experiments of Prof. Stokes seem to indicate that the 

 heematin of chemists is really a product of chemical 



