28 THE PHENOMENA OF COAGULATION. [BOOK I. 



the walls of the vessel have become gelatinized, occurs on an average 

 in the blood of men in 5 minutes 52 seconds, and in that of women 

 in 5 minutes 12 seconds; the third stage, in which the blood has been 

 converted throughout into a soft jelly, is usually developed in the 

 blood of men in 9 minutes 5 seconds, and in that of women in 

 7 minutes 40 seconds; the fourth stage, of complete solidification 

 with obvious commencement of transudation of serum from the clot, 

 occurs in the blood of men in about 11 minutes 45 seconds, and in 

 that of women in 9 minutes 5 seconds 1 . 



This process of coagulation is due to the separation from the 

 plasma of a body called Fibrin, which entangles in its meshes the 

 corpuscles of the blood, the mechanical interlocking of the corpuscles 

 by the threads of fibrin giving rise to the crassamentum or blood clot. 



The blood of certain animals coagulates more rapidly than that 

 of others : we might with fair accuracy arrange the blood of various 

 common domestic animals in the following order, according to the 

 rapidity of coagulation, the first-named coagulating most rapidly 

 rabbit, sheep, dog, ox, horse ; in the latter animal coagulation com- 

 mences usually between five and ten minutes after the blood is shed. 

 If human blood were included in the above list it would immediately 

 precede that of the ox. 



When the commencement of coagulation is delayed for several 

 minutes as it normally is in horse's blood, and as it usually is in 

 the blood of men and other animals when suffering from inflammatory 

 diseases the blood corpuscles, being specifically heavier than the 

 plasma, have time to subside partially before coagulation commences, 

 so that the uppermost layers of such blood if undisturbed are 

 nearly free from coloured corpuscles ; subsequently when the blood 

 coagulates, the clot exhibits the phenomenon of the huffy-coat, 

 'inflammatory crust/ or crusta phlogistica, i.e. the upper part of the 

 clot is of a yellowish colour ; in the lower strata of the buffy-coat are 

 found large numbers of colourless corpuscles, which being specifically 

 lighter than the red have not time to sink as far as the latter before 

 coagulation occurs. The formation of the buffy-coat, though in part 

 due to slow coagulation, is dependent greatly upon the blood cor- 

 puscles aggregating so as to form little clumps, which more readily 

 overcome the resistance offered by the fluid and therefore sink more 

 readily than individual corpuscles. 



If instead of allowing blood to coagulate undisturbed, it be 

 stirred or whipped with twigs immediately after it is shed, the process 

 of coagulation is modified. The fibrin generators unite to form fibrin, 

 but this does not entangle the blood corpuscles ; it separates as a 

 stringy mass, which adheres to the instruments which have been 

 used to stir the blood, whilst the blood corpuscles remain suspended 

 in the serum, the mixture being designated defibrinated blood. 

 Defibrinated blood differs from the living blood which has yielded it, 



- Nasse, Article Blut, Wagner's Handtvorterluch d. Physiologic, Vol. i. pp. 102, 103. 



