292 DISTURBANCES OF CIRCULATION 



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

 stitutes about five-sixths of the total alkali. 



The concentration of the electrolytes of the blood has been determined by 

 ascertaining the lowering of the freezing-point, which in human blood averages 

 about 0.526°; this corresponds closely to the effect of a salt solution of 0.9 per 

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

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

 of which are in the dissociated state.^ The calcium content is very constant, about 

 9 to 11 mg. per 100 cc. of plasma. 



Enzymes. — A large number of enzymes exist in the blood, the following being 

 among those that have been detected: diastase, glucase, lipase, thrombin, rennin, 

 and 'proteases. The proteases and perhaps the other enzymes are held in check 

 to a large extent by " antiferments" that are also present (see "Enzymes")- In 

 relation to the antiferments are the innumerable antibodies that exist normally 

 in the serum for foreign proteins, foreign cells, and for bacteria and their toxins, 

 as well as those resulting from reaction, etc. 



The proportions in which the constituents of the plasma normally occur have 

 been determined by Hoppe-Seyler and by Hammarsten, as follows:* 



Table I 



No. 1 No. 2 



Water 908.4 917.6 



SoUds 91.6 82.4 



Total proteins 77 . 6 69 . 5 



Fibrin 10.1 6.5 



Globulin 38.4 



Seralbumin 24 . 6 



Fat 1.2 



Extractive substances 4.0 



Soluble salts 6.4 12.9 



Insoluble salts 1.7 



No. 1 is an analysis by Hoppe-Seyler. 



No. 2 is the average of three analyses made by Hammarsten. 



Reaction. — If we titrate the blood plasma with an acid, we liberate much of 

 the alkali from the proteins, dissociate all the Na2C03 present, as well as the 

 NaHCOs and the sodium phosphate, and find in this way that the entire fresh 

 blood contains neutralizable alkali corresponding tc a solution of Na^COs of about 

 0.443 per cent, strength (Strauss;. In other words the blood has a quantity of 

 alkali in combination that can be drawn upon to neutralize acids to the extent 

 indicated by the above figures. The real alkalinity of a fluid, however, is dependent 

 upon the number of free OH ions in the solution; and Hober has determined by 

 physico-chemical methods that the concentration of OH ions in blood is but little 

 greater than in distilled water.'' Michaelis* has found the H+ concentration of 

 the blood to be 0.45 X 10"', as contrasted with neutrality at 38° which is H4- = 

 1.5 X 10~'. The interchange between COo, phosphates and carbonates in the 

 blood is such that it is impossible for any considerable quantities of free H or 

 OH ions to exist, and the protoplasm is thus protected from an excess of either. 

 The capacity of the blood to neutralize acids and alkalies is sometimes referred to 

 as its "buffer value."^ According to Henderson'" not more than five parts of 

 excess free H or OH ions can be present in ten billion parts of protoplasm. An 

 alkalinity is impossible because this would cause an increased osmotic pressure which 

 the kidneys would regulate; acidity is impossible because death would result 



^ Concerning relation of conductivity to freezing-point see Wilson, Anier. Jour, 

 of Physiol., 1906 (16), 438. 



'^ For complete analyses of the blood see Abderhalden, Zeit. physiol. Chem., 

 1S9.S (25), 106. 



' For bibliography on Alkalinity of Blood, see Henderson, Ergcbnisse Physiol., 

 1909 (8), 254. 



8 Deut. med. Woch., 1914 (40), 1170. 



" See Levy and Rowntree, Arch. Int. Med., 1916 (17), 525. 



»" Amer. Jour. Physiol., 1907 (18^. 250; 1908 (21;, 427. 



