164 BLOOD. 



blood-corpuscles, and that horses' blood, in which the cells sink 

 with unparalleled rapidity, contains an especially viscid and 

 tenacious serum. Whatever probability this view might at first 

 sight appear to possess, it will not bear a closer scrutiny : inflam- 

 matory blood, in which we most frequently observe an increased 

 rapidity in the sinking of the red corpuscles, never contains an 

 excess of albumen, but, on the contrary, generally contains less 

 than normal blood ; solutions of sugar and gum hasten the sinking 

 of the corpuscles, but deprive them of their property of cohering ; 

 and lastly, the corpuscles of horses' blood sink in the serum of 

 human or other animal blood with almost the same rapidity as in 

 their own serum ; whilst the corpuscles of other animals, when 

 placed in the serum of horses' blood, do not by any means exhibit 

 a great tendency to sink. Generally speaking, physical considera- 

 tions do not appear to support this view. For if the viscidity of a 

 fluid depends on the amount of r ^traction which its molecules 

 exhibit towards each other, the cohesion of the particles of 

 fluid must overcome the adhesion to the cell-walls ; hence no 

 cohesion of the blood-cells can be directly dependent on the 

 viscidity of the fluid ; but if the viscidity of the fluid consists in 

 the fact that its molecules exhibit a greater attraction to the cell- 

 walls than to one another, every cell must be surrounded by a 

 sphere of fluid by which its closer contact with other cells (and 

 consequently the aggregation of the cells generally) is prevented ; 

 moreover, we find that in emulsions the aggregation of the sus- 

 pended molecules diminishes in proportion to the tenacity and 

 viscidity of the emulsive solution. Hence Nasse was led to seek 

 the cause of this aggregation, not in the fluid, but in the corpus- 

 cles themselves that is to say, in a viscid property of their 

 capsules ; he referred especially to the action of carbonic acid. An 

 abundance of carbonic acid in the blood (whether caused by an 

 imperfect interchange of gases in the lungs, or artificially intro- 

 duced into it,) is certainly usually accompanied by a rapid sinking 

 of the blood- corpuscles. But that the membrane of the blood- 

 corpuscle, or that its contents should actually be rendered more 

 viscid by carbonic acid, would not be inferred from the converse 

 experiment that oxygen and salts communicated to the blood- 

 corpuscles a clearly defined, smooth, although often folded 

 surface ; for a solution of sugar acts on the form of the corpus- 

 cles, as far as the change can be followed by the microscope, in 

 just the same manner as salts, and yet induces a rapid sinking of 

 the red blood -cells. Moreover, it is hardly probable that carbonic 



