20 OKGANIBED FLUIDS. 



labouring all the while under severe inflammation. An 

 ignorance of this fact has been the source of many great and 

 perhaps fatal errors, on the part of those physicians who have 

 been used to regard the presence of the buffy coat as an un- 

 doubted evidence of the existence of inflammation, and its 

 absence as indicating immunity therefrom. It has been 

 remarked that, in the first bleedings of pneumonic patients, 

 the blood often wants the buffy coat : this is attributed to 

 its greater density, and which is found to diminish with each 

 succeeding abstraction of blood ; so that if inflammation be 

 present, the characteristic coat is usually apparent also after 

 the second bleeding. 



The conditions, then, favourable to the formation of the 

 buffy coat, are a mean density of the blood, slow coagulation ; 

 excess of fibrin, and increased disposition to adherence on the 

 part of the red corpuscles. 



Other circumstances doubtless exist, which in a minor 

 degree affect the formation of the crust : such as the density 

 of the globules, and the qualities of the fibrin itself. Into 

 these it is unnecessary to enter, as they do not vitiate the 

 accuracy of the general statements. 



The Cupping of the Clot. 



At the same time that the crassamentum exhibits the 

 buffy coat, the upper surface of the clot is very generally 

 also cupped. This cupping of the clot arises from the con- 

 traction of that portion of the fibrin which constitutes the 

 buffy stratum, and which contraction operates with greater 

 force on account of the absence in it of the red corpuscles of 

 the blood. The degree to which the clot is cupped, therefore, 

 probably is in direct relation with the thickness of the crust. 

 Its presence was also regarded as an indication of the existence 

 of inflammation, the amount of cupping denoting the extent 

 of inflammation. This sign is not, however, any more than 

 that afforded by the buffy coat, to be considered as an in- 

 variable criterion of the existence of inflammation.* 



* Professor Nasse has pointed out a mottled appearance which is 



