BLOOD. 49 



colored liquid, the scrum, which gradually increases in quantity as the clot 

 diminishes in size, by contraction, until the separation is completed, which 

 occupies from 12 to 24 hours. 



The changes in the blood are as follows : 



Before coagulation. 



f Liq. Sanguinis "j f Water. 



or V Consisting, of J Albumin. 



Living blood, -j Plasma. J | Fibrinogen. 



L Salts. 



[ Corpuscles. Red and white. 

 After coagulation. 



f Crassamentum. 1 n . . . f Fibrin. 



I Clot or coagulum. / Containing \ Corpuscles. 



Dead blood, -j f Water. 



| Serum. Containing -] Albumin. 



L I Salts. 



The serum, therefore, differs from the Liquor Sanguinis in not containing 

 fibrin. 



In from 12 to 24 hours the upper surface of the clot presents a grayish 

 appearance, the buffy coat, which is due to the rapid sinking of the red 

 corpuscles beneath the surface, permitting the fibrin to coagulate without 

 them, which 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 cor- 

 puscles, 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 blood, but is formed at the moment blood is withdrawn from the vessels.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, plasmine, exists in the blood, 

 which, when withdrawn from the circulation, decomposes m^o fibrin and 

 met-albumin. 



According to Schmidt, fibrin results from the union of fibrinoplastin 

 (paraglobulin) and fibrinogen, 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 substance, paraglobulin in this 



