290 DISTURBANCES OF CIRCULATION 



per cent, of cholesterol (Hoppe-Seyler) . The outer coat of tlie red corpuscles 

 does not seem to be equally permeable for all substances, and tlierefore we find 

 the composition of the fluid portion of the cell quite different from tliat of the 

 plasma about it. The salts of the corpuscles consist largely of potassixun ])hos- 

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

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

 stituents of the plasma, especially urea, penetrate 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 lecitliin. It splits 

 up readily into a protein, glohin, and an iron-cont^iining substance, he^nochromo- 

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

 of the hemoglobin is heniochromogen, 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 probaldy some globulin, 

 and they also contain glycogen, lecithin, and cholesterol. The hiood-pUitclrts are 

 believed to Ik^ largely nucleoprotein, but little is known of tlicir actual composi- 

 tion; miiTocliciuical examination shows no evidence of either fat or glycogen. 2 



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

 former through the conversion of the fibrinogen 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 funda- 

 mentally a tissue, with its more solid structural elements lying in a protoplasm, 

 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. (Tliis process will be 

 discussed imder "Thrombosis.") In the plasma are also other globulins.-'a one 

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

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

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

 coagulable proteins, which being poorly understood have been variously considered 

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

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



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

 which has elapsed after tlie taking of f^od ; in fasting animals it amounts to from 

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

 while the urea has been estimated at 0.05 per cent. ]\Tost of the sugar is dex- 

 trose; but probably there is some levulose, possibly some pentose and otlier forms, 

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

 Soaps, cholesterol, and lecithin also exist free in the plasma. 



Plasma difTers strikingly from the corpuscles in that its inorganic substances 

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

 entirely absent. Another imjiortant fact is that wIumi the plasma is combusted, 

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

 much of tlie inorganic bases is joined with organic sulistances. probably as ion- 

 protein compounds. The alkali joined to tlie protein is non-diffusible, and con- 

 stitutes aliout five-sixths of tlie total alkali. 



The concentration of the electrolytes of the blood has been determined ^ly 

 ascertainiiiir iht> lowering of the f-ce/jim-iioint, which in human Idood averages 

 about 0..52(i° ; this corresponds closcb- to the efi'ect of a salt solution of 0.0 per 

 cent, strength. About three-fcnirtlis of the dissolved molecules of the blood-serum 

 are electrolytes, and about three-fourths of these an* molecules of NaCl. most 

 of which are in the dissociated states 



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

 by Ilamlnirgcr (Zeit. physikal. ("hem.. 1000 (CO), C0.3). 

 " 2 Ayiiaud. Ann. Inst. Pasteur, 1011 (25), 56. 



2a Literature given by Powe. Arch. Int. j\Ied.. lOlfi (IS), 455. 



3 Concerning relation of conductivil v to free/.ing-poiiif see Wilson. .Xmer. .Tour, 

 of Physiol., 1006 (16), 438. 



