272 THE BLOOD. 



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 CO3 is in aqueous solution more or less dissociated into 

 2Na + and COa", depending upon the dilution. The C0s = 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, 

 the equilibrium is then disturbed, a new quantity of Na 2 COs 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 we generally determine the quantity of HO 

 and H ions in the serum and blood by methods based upon NERNST'S 

 theory for the electromotive force of gas-chains. According to these 

 investigations it has been found that the concentration of the hydroxyl 

 ions in blood-serum and blood is only a little higher than in distilled 

 water (see Chapter I page 76, and the reaction of the blood below). 



H. THE FORM-ELEMENTS OF THE BLOOD. 

 The Red 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 Cyclostoma) the cor- 

 puscles have in general a nucleus, are biconvex and more or less ellip- 

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

 diameter of 7 to 8 /i (M= 0.001 mm.) and a maximum thickness of 1.9 /z. 

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

 in these liquids. In the discharged blood they may sometimes lie with 

 their flat surfaces together, forming a cylinder like a roll of coin (rouleaux) . 

 The reason for this phenomenon, which is considered as an agglutination, 

 has not been sufficiently studied, but as it may be observed in defibrinated 

 blood it seems probable that the formation of fibrin has nothing to 

 do with it. 



The number of red blood-corpuscles is different in the blood of various 

 animals. In the blood of man there are generally 5 million red cor- 

 puscles in 1 c.mm., and in woman 4 to 4.5 million. 



The blood-corpuscles consist principally of two chief constituents, 

 the stroma, which forms the real protoplasm, and the intraglobular 

 contents, whose chief constituent is haemoglobin. We cannot state 



