THE COMI'OHITIOX OF THE BLOOD 291 



Enzymes. — A large number of enzymes exist in tlie blood, the followiufi; being 

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

 and proteases. The proteases and [lerhaps the other enzymes are held in elieck 

 to a large extent by ''antifer7HCtits'' that are also present (see "Hnzyines'") . In 

 relation to the antiferments are the innumerable antibodies tiiat exist normally 

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

 as well as those resulting from reaction to infection, etc. 



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

 been determined by Hoppe-Seyler and by Ilammarsten as follows: * 



Table I 



No. 1 Xo. 2 



Water 908.4 1)17.6 



Solids 91.6 S2.4 



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 ^'^•^ 



"^ Insoluble salts 1.7 



No. 1 is an analysis by Hoppe-Seyler. 



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



Reaction. — It i.s very difficult to determine the exact reaction of 

 tlie blood plasma. If we titrate with an acid, we liberate much of 

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

 as the NaHCO.j and the sodium phosphate, and find in this way that 

 the entire fresh blood contains neutralizahle alkali corresponding to a 

 solution of NajCOg 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 de- 

 termined 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 H+ = 1.5 X 10"^ The in- 

 terchange 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 Hen- 

 derson ^ not more than five parts of excess free H or OH ions can be 

 present in ten billion parts of protoplasm. An alkalinity is impos- 

 sible because this would cause an increased osmotic pressure which 



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

 1898 (25), 106. 



^> For bibliograpbv on Alkalinity of Blood, see Henderson, Ergebnisse Physiol., 

 1909 (8), 254. 



saDeut. med. Woch.. 1914 (40). 1170. 



5b See 'Levx and Rowntree. Arch. Int. Med., 1916 (17), 525. 



6 Amer. Jour. Phvsiol., 1907 (18), 250; 1908 (21), 427. 



