264 THE BLOOD. 



found that about three-fourths of the total number of dissolved mole- 

 cules in blood-serum were electrolytes, although the serum contained 

 about 70-80 p. m. protein and 10 p. m. inorganic bodies, and also that 

 three-fourths of the quantity of electrolytes consisted of NaCl. 



In the determination of the alkalinity of blood and blood-serum, 

 up to the present time we have estimated the amount of alkali by titra- 

 tion with an acid. We cannot dispense with such determinations, although 

 they do not yield any information as to the true alkalinity, apart from 

 the fact that the results are dependent upon the indicator used, because 

 we understand as true alkalinity the concentration of the hydroxyl 

 ions. The Na 2 CO 3 is in aqueous solution more or less dissociated into 

 2Na + and CO3 = , depending upon the dilution. The C0 3 = ions com- 

 bine partly with the H + ions of the dissociated water, forming HCOa~, 

 and the corresponding HO~ ions produce the alkaline reaction. If now 

 by the addition of a little acid, a few of the HO~~ ions are removed, 

 then the equilibrium is disturbed, a new quantity of Na 2 CO3 is dissociated, 

 and this process is repeated every time a new quantity of acid is added 

 until all the carbonate is dissociated. The dissociation of the carbonate 

 existing in* the original concentration, upon which the number of HO~ 

 ions is dependent, cannot therefore be determined by titration. For 

 these reasons HOBER has worked out a physical-chemical method of 

 determining alkalinity, based upon NERNST'S theory of liquid chains. 

 This method was used later by FARKAS, FRANCKEL, and HOBER after 

 a few changes. The investigations of these last-mentioned experimenters 

 show that the concentration of the hydroxyl ions in blood-serum and 

 blood is nearly the same as in distilled water, and that these fluids are 

 nearly neutral in behavior, which is accounted for by the presence of car- 

 bonic acid. FRiEDENTHAL, 1 by testing serum with phenolphthalein, arrived 

 at similar results. 



II. THE FORM-ELEMENTS OF THE BLOOD. 

 The Bed Blood-corpuscles. 



The blood -corpuscles are round, biconcave disks without membrane 

 and nucleus in man and mammalia (with the exception of the llama, 

 the camel, and their congeners). In the latter animals, as also in birds, 

 amphibia, and fish (with the exception of the Cy clostoma) , the corpuscles 

 have in general a nucleus, are biconvex and more or less ellipitical. The 

 size varies in different animals. In man they have an average diameter 

 of 7 to 8 /j. (/z^O.OOl mm.) and a maximum thickness of 1.9 /.. They 

 are heavier than the blood-plasma or serum, and therefore sink in these 



1 Hober, Pfluger's Arch., 81 and 99; Farkas, see Biochem. Centralbl., 1, 626; 

 Franckel, Pfluger's Arch., 96; Friedenthal, Zeitschr. f. allg. Physiol., 1 and 4. 



