CHAP, i.] BLOOD. 51 



90 parts are haemoglobin, about 8 parts are proteid substances, 

 and about 2 parts are other substances. Of these other substances 

 one of the most important, forming about a quarter of them and 

 apparently being always present, is lecithin. Cholesterin appears 

 also to be normally present. The proteid substances which form 

 the stroma of the red corpuscles appear to belong chiefly to the 

 globulin family. As regards the inorganic constituents, the cor- 

 puscles are distinguished by the relative abundance of the salts 

 of potassium and of phosphates. This at least is the case in man ; 

 the relative quantities of sodium and potassium in the corpuscles 

 and serum respectively appear however to vary in different animals ; 

 in some the sodium salts are in excess even in the corpuscles. 



37. The proteid matrix of the white corpuscles, we have 

 stated to be composed of myosin (or an allied body) paraglobulin, 

 and possibly other proteids. The nuclei contain nuclein. The 

 white corpuscles are found to contain in addition to proteid ma- 

 terial, lecithin and other fats, glycogen, extractives and inorganic 

 salts, there being in the ash as in that of the red corpuscles a pre- 

 ponderance of potassium salts and of phosphates. 



The main facts of interest then in the chemical composition of 

 the blood are as follows. The red corpuscles consist chiefly of 

 haemoglobin. The organic solids of serum consist partly of serum- 

 albumin, and partly of paraglobulin. The serum or plasma 

 contrasts in man at least, with the corpuscles, inasmuch as the 

 former contains chiefly chlorides and sodium salts while the latter 

 are richer in phosphates and potassium salts. The extractives of 

 the blood are remarkable rather for their number and variability 

 than for their abundance, the most constant and important being 

 perhaps urea, kreatin, sugar, and lactic acid. 



42 



