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XXI. Some observations on the huffy coat of the Blood, &c. By 
John Davy, M. D. F. R . S. 
Read April j8, 1822. 
1. The buffy coat, as it is technically called, which appears 
on blood drawn from persons labouring under inflammatory 
disease, has been referred, by Mr. Hewson, to two circum- 
stances ; to increased tenuity of the blood, and to its slow 
coagulation.* But, in the explanation which is now usually 
given of the phenomenon, it is attributed to the latter circum- 
stance, to the entire neglect of the former. The reverse of 
this, I believe, would be more correct ; for in cases in which 
the inflammatory diathesis is best marked, the separation of 
the red particles from the blood drawn is most rapid, often 
occurring in one or two minutes ; and, in some diseases, par- 
ticularly in erysipelas, the blood taken from a vein coagulates 
as rapidly as healthy blood, and yet exhibits the buffy coat. 
In instances of this kind, when I have watched the coagula- 
tion of the blood, the red particles have subsided in the short 
space of two minutes, leaving a supernatant stratum of coagu- 
lable lymph, transparent and liquid. The buffy coat, in these 
instances, did not appear on the blood collected in the com- 
mon bleeding cups, only when small vessels, as wine-glasses, 
or small gallipots were used, and quickly filled, and instantly 
set aside to rest. May it not, therefore, be inferred generally, 
* “ An Experimental Inquiry into the Properties of the Blood, with Remarks on 
some of its Morbid Appearances.” By William Hewson, F. R. S. London, 1771, 
p. 56 and 59. 
