THE CORPUSCLES OF THE BLOOD. 



41 



skin or the bowels, that water comes really from the blood, and the drain 

 of water must tend to diminish the bulk of the plasma, and so to increase 

 the relative number of red corpuscles, though the effect is probably soon 

 remedied by the passage of water from the tissues into the blood. So 

 again when a large quantity of water is drunk, this passes into the blood 

 and tends temporarily to dilute the plasma (and so to diminish the relative 

 number of red corpuscles), though this condition is in turn soon remedied 

 by the passage of the superfluous fluid to the tissues and excretory organs. 

 The greater or less number of red corpuscles, then, in a given bulk of blood 

 may be simply due to less or more plasma, but we have reason to think that 

 the actual number of the corpuscles in the blood does vary from time to 

 time. This is especially seen in certain forms of disease which may be 

 spoken of under the general term of anaemia (there being several kinds of 

 anaemia), in which the number of red corpuscles is distinctly diminished. 



The redness of blood may, however, be influenced not only by the number 

 of red corpuscles in each cubic millimetre of blood, but also by the amount 

 of haemoglobin in each corpuscle, and to a less degree by the size of the 

 corpuscles. If we compare, with a common standard, the redness of two 

 specimens of blood unequally red, and then determine the relative number 

 of corpuscles in each, we may find that the less red specimen has as many 

 corpuscles as the redder one, or at least the deficiency in redness is greater 

 than can be accounted for by the paucity of red corpuscles. Obviously, in 

 such a case, the red corpuscles have too little haemoglobin. In some cases 

 of anaemia the deficiency of haemoglobin in each corpuscle is more striking 

 than the scantiness of red corpuscles. 



The number of corpuscles in a specimen of blood is determined by mixing a 

 small but carefully measured quantity of the blood with a large quantity of some 



[FIG. 8. 



Hsemacytometer of Gowers : A, pipette for measuring the diluting solution ; E, capillary tube 

 for measuring blood ; C, cell with divisions on slide, cover-glass and springs ; D, vessel to mix 

 solutions ; E, mixer ; F, guarded spear-pointed needle for sticking finger.] 



indifferent fluid, e. g., a 5 per cent, solution of sodium sulphate, and then actually 

 counting the corpuscles in a known minimal bulk of the mixture. 



