COMPOSITION OF BLOOD '291 



uents of the corpuscles, from 5 to 12 ywr cent, consist of proteins, i)robal)ly chiefly 

 globulins and nuclcoprolcins; 0.3 to 0.7 per cent, of lecithin; and about 0.2 to 0.3 

 per cent, of cholesterol (Iloppe-Seyler). The outer coat of the red corpuscles 

 docs not seem to be equally permeable for all substances, and therefore we find 

 the composition of the fluid p(jrtion of the cell quite different from that of the 

 plasma about it. The salts of tlie corpuscles consist largely of potassium pho.s- 

 phate, a little sodium chloride, some magnesium, but no calcium,' which is quite 

 different from their proportion in the plasma. Probably many of the other con- 

 stituents of the plasma, especially urea, ])enetrate the red corpuscles to a greater 

 or less degree, but most of them, particularly the sugar, remain chiefly in the 

 plasma. 



Hemoglobin, the most characteristic constituent of all the heterogeneous com- 

 ponents of the blood, is a compound protein, and probably exists combined with 

 some other constituent of the corpuscle, most probably the lecithin. It splits 

 up readily into a protein, glohin, and an iron-containing substance, hemochromo- 

 gcn, which readily takes up oxygen to form hematin. Only about 4 to 5 per cent, 

 of the hemoglobin is hemochromogen, and iron constitutes but about 0.4 per cent. 

 Hematin may be further split up into other substances, which will be considered 

 in the discussion of "Hemorrhage." 



The leucocytes consist chiefly of nucleoproteins, with probably some globulin, 

 and they also contain glycogen, phospholipins, and cholesterol. The blond-platelets 

 are believed to be largely nucleoprotein, but little is known of their actual composi- 

 tion; microchemical examination shows no evidence of either fat or glycogen.* 



BLOOD PLASMA differs from blood-serum in that the latter is formed from the 

 former through the removal of the fibrinogen through its conversion into fibrin. 

 Serum, therefore, contains no fibrinogen, but more fibrin ferment; otherwise it 

 is practically the same as the plasma.^ It is well for us to appreciate that the blood 

 is fundamentally a tissue, with its more solid structural elements lying in a pro- 

 toplasm, the plasma, somewhat more dilute than the protoplasm of other tissues 

 but in other respects much the same. 



Proteins. — Fibrinogen has the general properties of a globulin, with also a 

 peculiar tendency to go into the insoluble form, fibrin. (This process will be 

 discussed under "Thrombosis.") In the plasma are also other globulins,'* one 

 soluble in water (pseudo-globidin), the other insoluble in water {euglobulin) . 

 Serum-albumin, another protein of the plasma, probably consists of two or more 

 varieties of albumin. There are also nucleoproteins {prothrombin) and non- 

 coagulable proteias, which being poorly understood have been variously considered 

 as glycoproteins, or mucoids, or albumoses. The serum proteins seem to be closely 

 related to, or compounded with, the lipins of the plasma. 



Other Constituents. — The fat of the plasma varies much according to the time 

 which has elapsed after the taking of food; in fasting animals it amounts to from 

 0.1 to 0.7 per cent. The sugar fluctuates less, being normally about 0.1 per cent., 

 whUe the urea has been estimated at 0.03 per cent. Most of the sugar is dex- 

 trose; but probablj' there is some levulose, possibly some pentose and other forms, 

 and possibly also sugar combined with lecithin (jccorin) or other substances. 

 Soaps, cholesterol, and phospholipins exist free in the plasma. There are also the 

 numerous nonprotein nitrogenous substances that are excreted in the urine. 



Plasma differs strikingly from the corpuscles in that its inorganic substances 

 are chiefly sodium and chlorine, while potassium and phosphoric acid are almost 

 entirely absent. Another important fact is that when the plasma is combusted,, 

 the acid radicals remaining do not suffice to balance the bases, indicating that 

 much of the inorganic bases is joined with organic substances, probabh' as ion- 



' The current statement that corpuscles are impermeable for calcium is refuted 

 by Hamburger (Zeit. physikal. Chem., 1909 (69), 663). 



- Aynaud, Ann. Inst. Pasteur, 1911 (25), 56. 



^ In the process of clotting certain changes occur, probablj^ physical, that may 

 make the plasma more or less toxic (see Anaphyla.xis) and apparently alter its 

 biological properties, since the reinjection of a person's own defibrinated serum 

 may cause marked physiological and therapeutic effects {e. g., autoserotherapy 

 in psoriasis). Especially noteworthv is the vasoconstrictor effect of defibrinated 

 blood (see Hirose, Arch. Int. Med., 1918 (21), 604). 



* Literature given by Rowe, Arch. Int. Med., 1916 (18), 455. 



