COAGULATION OF THE BLOOD. 249 



tion, the corpuscles are displaced and escape into the serum, 

 which is thus stained and cannot be seen in its clear, transparent 

 state. 



If brisk agitation with a glass rod or, better, a bundle of 

 twigs be commenced the moment the blood is drawn, the fibrin 

 is formed more rapidly, but the corpuscles are not entangled in 

 its meshes, for as quickly as the elastic threads are formed they 

 adhere firmly to the rod or twigs. Thus the fibrin is formed very 

 rapidly, and the ordinary blood clot, consisting of fibrin and the 

 corpuscles, does not appear, for the fibrin is separated from the 

 latter during the coagulation. We then have what is commonly 

 spoken of as " defibrinated blood," which does not give a clot. 

 Not that the clotting has been prevented, but the material essen- 

 tial for the formation of a clot has been removed as quickly as 

 formed, and instead of catching the corpuscles in the meshes of its 

 delicate fibrils to form the clot in the ordinary way, the stringy 

 shreds of fibrin cling around the beating-rod as a jagged mass. 

 The following tables show the relation of the different constitu- 

 ents of coagulated and defibrinated blood respectively : 



C Serum (appearing as clear 



f Plasma ) fluid). 



Living Blood = < ~ . \ = -I _., . ' 



\ Corpuscles J 1 Fibrin 1 _. , . x 

 ~ . > Blood clot. 



V Corpuscles ) 



Fibrin (removed on the 

 rod). 



^ = Defibri- 

 Serum , 



~ , > nated 



Corpuscles 



T T>I j f Plasma ) 



.Living Blood = < ~ , > = 



( Corpuscles J 



Many circumstances influence the rapidity with which a 

 blood clot is formed. Speaking generally, the removal of the 

 blood from its normal supply of nutrition and from the oppor- 

 tunity of preserving the necessary equilibrium of chemical inter- 

 change between the corpuscles, the plasma, and the tissues in 

 short, circumstances which tend to injure the corpuscles or the 

 plasma, and promote the changes resulting in their death must 

 hasten coagulation ; while, on the other hand, the conditions 



