THE BUFFY COAT. 203 



an excess of colourless blood-cells and vesicles of fat in the crust, 

 than upon the slight contractility of the fibrin. 



Although this mode of explaining the formation of a fibrinous 

 or buffy coat scarcely needs any additional grounds for its 

 establishment, Miiller, H. Nasse, and Henle have confirmed it by 

 special experiments ; for they formed an artificial buffy coat from 

 blood that was not buffed, by employing means either for accele- 

 rating the sinking of the blood-cells, or for retarding the coagula- 

 tion of the fibrin. Nasse found, moreover, on comparing the 

 blood of different animals, and by closely examining diseased buffy 

 blood, that the time in which the blood-corpuscles sink bears an 

 inverse relation to that in which the fibrin coagulates. Nasse and 

 others have, however, also frequently seen cases in which rapidly 

 coagulating blood formed a buffy coat; these instances do not, 

 however, present any exception to the rule, since they only show 

 that the sinking of the corpuscles has proceeded more rapidly 

 than the coagulation of the fibrin. 



We must not omit all mention of certain relations which, 

 although they do not constitute the sole conditions necessary for 

 the formation of a buffy coat, may contribute simultaneously with 

 other causes towards its production. Among these we must first 

 instance the form of the vessel in which the blood is suffered to 

 coagulate. In a high narrow vessel, the blood- corpuscles are 

 sooner removed from the level of the fluid than in a wide and 

 shallow one, and thus leave a part of the fibrin to coagulate 

 without them ; on this account, strongly inflamed blood is often 

 found to yield no buffy coat in a flat vessel, whilst, on the 

 contrary, blood which is considered to be of a non-inflam- 

 matory character exhibits a buffy coat if received in a narrow 

 cylinder. 



The number of the corpuscles is another cause which contri- 

 butes to the formation of this coat. When the number of 

 corpuscles is small and their sinking capacity is considerable, a 

 buffy coat will more readily be formed than where the blood- 

 corpuscles are present in large numbers. On this account a buffy 

 coat is more frequently formed after a second or third, than after 

 the first venesection The same cause explains its more frequent 

 occurrence in the blood of anaemic and pregnant females, than in 

 that of healthy and non-pregnant women. 



It was formerly regarded as a well-established view, that the 

 formation of this coat was owing to an excess of fibrin ; and as the 

 increase of the fibrin was in general proportional to the progress 



