128 HUMAN PHYSIOLOGY. 



(Liq. Sanguinis, ^ r Water. 



Albumin, 

 or ^consisting of J 



1 Fibrinogen. 

 Plasma, J [ Salts. 



Corpuscles, red and white. 

 After coagulation. 



" assamentum. | c Fibrin. 



Clot or coagulum, / 1 Corpuscles. 



Dead blood. J f Water. 



Serum, containing -s Albumin. 



[ Salts. 



The serum, therefore, differs from the liquor sanguinis in not 

 containing fibrin. 



In from twelve to twenty-four hours the upper surface of the clot 

 presents a grayish appearance, the buffy coat, owing to the rapid 

 sinking of the red corpuscles beneath the surface, permitting the 

 fibrin to coagulate without them ; this substance then assumes a 

 grayish-yellow tint. Inasmuch as the white corpuscles possess a 

 lighter specific gravity than the red, they do not sink so rapidly, 

 and, becoming entangled in the fibrin, assist in forming the buffy 

 coat. Continued contraction gives a cupped appearance to the 

 surface of the clot. 



Inflammatory states of the blood produce a marked increase in the 

 buffed and cupped condition, on account of the aggregation of the 

 corpuscles and their tendency to rapid sinking. 



Nature of Coagulation. Coagulated fibrin does not preexist 

 in the blood, but is formed at the moment blood is withdrawn from 

 the vessels. According to Denis, a liquid substance plasmin 

 exists in the blood, which, when withdrawn from the circulation, 

 decomposes into fibrin and metalbumin. 



According to Schmidt, fibrin results from the union of fibrino- 

 plastin (paraglobulin) and nbrinogen, brought about by the presence 

 of a third substance, the fibrin-ferment. 



According to Hammersten and others, the fibrin obtained from 

 the blood after coagulation comes from the fibrinogen alone, the 

 conversion being brought about by the presence of a ferment sub- 

 stance, paraglobulin in this case having nothing to do with the 

 change. This view is supported by the fact that the quantity of 

 fibrin obtained from the blood is never greater than the quantity 



