ORGANIC PRINCIPLES. 77 



gives us no indication of the properties by which it is recog- 

 nized, nor of its functions ; and, indeed, has been found to 

 differ little, if at all, from the composition of musculine or 

 albumen, the properties of which are very different. 



Fibrin may be easily extracted from the fluids in which 

 it exists. Perhaps the best mode of procedure is to whip 

 the fluid, freshly drawn, with a bundle of twigs or broom 

 corn. In this way the fibrin may be quickly and completely 

 separated. It is then freed from foreign matters, such as 

 blood-corpuscles, by washing under a stream of water, at the 

 same time kneading with the fingers: 



Fibrin is not, as is supposed by many, a solid substance 

 in solution in the liquids in which it is found. It is naturally 

 liquid and mingled with the watery elements. After coagu- 

 lation it contains a certain proportion of water, capable, it is 

 true, of being driven off by evaporation, but nevertheless 

 water of composition, deprived of which it loses the prop- 

 erties by which we recognize it as fibrin. 



Properties of Fibrin. The striking peculiarity by which 

 fibrin is recognized is its spontaneous coagulability. All the 

 fluids in which it is contained, when drawn from the body or 

 placed under abnormal conditions, become more or less 

 coagulated, and their coagulating principle is called fibrin. 

 It is this substance, therefore, which gives to the blood its 

 peculiar and important property of coagulability. The con- 

 dition under which fibrin coagulates seems to be that of stasis. 

 Whenever it is drawn from the body, or in the vessels, when 

 circulation becomes arrested, it assumes, after a variable time, 

 a semi-solid consistence. The cause of this remarkable phe- 

 nomenon was obscure until the essay of Richardson on the 

 " Cause of the Coagulation .of the Blood" appeared in 1856. 

 By a series of carefully conducted experiments, this observer 

 demonstrated that the blood contains a small quantity of free 

 ammonia, which has the power of maintaining the fibrin in its 

 liquid condition. This ammonia is being continually devel- 



