RED, WHITE AND COLOURLESS BLOOD-CORPUSCLES. 187 



liarity is simply explained by the different specific gravity 

 of the two kinds of blood-corpuscles. The colourless 

 ones are always light, poor in solid matter and very deli- 

 cate in structure, whilst the red ones are as heavy as 

 lead in comparison, owing to their richness in haematine. 

 They therefore reach the bottom 

 with comparatively great rapidity, 

 whilst the colourless ones are still 

 engaged in falling. If two bodies of 

 different specific gravities be allowed 

 to fall from a sufficient height in the 

 open air, the lighter one will, you 

 know, in a similar manner, reach the 

 ground after the other, owing to the 

 resistance of the air. 



In the coagulation which takes 

 place in blood derived from venaesection, this white clot 

 does not usually form a continuous, but an interrupted, 

 layer, composed of little heaps or nodules adhering to the 

 under side of the buffy coat. Hence Piorry, who was 

 the first to observe this appearance, but completely mis- 

 interpreted it, seeing that he referred it to an inflamma- 

 tion of the blood itself (Haemitis) and established the 

 doctrine of Pyaemia, upon it, termed this form of buffy 

 coat crusta granulosa. It really consists of nothing more 

 than large accumulations of colourless corpuscles. 



Under all circumstances this layer resembles pus in 

 appearance, and since, as we have already seen, the 

 colourless blood-cells individually are constituted like 

 pus-corpuscles, you see that we are liable not only in the 

 case of a healthy person to take colourless blood-cells for 



Fig. 60. Diagram of a bleeding-glass with coagulated hyperinotic blood, a. The 

 level of the liquor sanguinis. c. The cup-shaped buffy coat. I. The layer of lymph 

 (Cruor lymphaticus, Crusta granulosa), with the granular and mulberry-like accumu- 

 lations of colourless corpuscles, r. The red clot. 



