162 BLOOD. 



the surrounding fluid would have been more equalized. We should 

 a priori have expected the very opposite namely, a diminished 

 sinking tendency. 



Before,, however, we proceed to notice the further causes of this 

 phenomenon, let us more closely consider the specific gravity of the 

 blood-corpuscles in its relation to that of the plasma. Since we 

 cannot so completely isolate the blood-corpuscles from the plasma 

 as to determine their specific gravity in a direct manner, it is only 

 by an indirect method that is to say, by a calculation based on 

 other determinations that we can ascertain their density in the 

 condition in which they exist in fresh blood. Moreover, it "will be 

 shown by a subsequent analysis of their proximate constituents, 

 that the blood-corpuscles of different specimens of blood must have 

 a variable specific gravity ; but it might even a priori be inferred 

 that their density must vary with the varying constitution of the 

 surrounding fluid, since a continuous diffusion-current exists 

 between the contents of the cell and the intercellular fluid. Hence 

 the density of the blood-corpuscles will not merely vary according 

 to the quantity of ferruginous haematin which they may contain, but 

 also according to their absorption or loss, according as they are in 

 solutions more or less concentrated than their own contents ; 

 indeed, we shall presently see that the density of the blood-cells is 

 far more dependent on the substances which are taken up or given 

 off by endosmosis, than on the quantity of hsematin they may 

 contain ; for this latter is far less variable than the quantity of 

 water, and is also partially compensated for by an augmentation or 

 diminution of fat in the blood-cells. The blood-corpuscles of 

 healthy human blood have a density which, in man, varies from 

 1-0885 to 1-0889, and in woman, from 1'0880 to 1'0886. In 

 diseases, the density is not confined within these limits. Thus, in 

 cholera, Schmidt found that the specific gravity of the blood-cells 

 was increased to 1'1025 or even to 1*1027, while in dysentery it was 

 diminished to 1*0855, in albuminuria to 1*0845, and in dropsies 

 to 1*0819. 



We are indebted to the intelligence and indefatigable perse- 

 verance of C. Schmidt* for our knowledge of the density of the 

 blood-corpuscles, as well as for many other discoveries in relation 

 to the blood ; when, in accordance with the method presently to 

 be given, we have determined the weight of the moist corpuscles 

 occurring in a specimen of blood, their density may be easily found 

 by a simple equation, as soon as the specific gravities of the serum 



* Op. cit. 



