20 Cheruual Properties of Animal Fh. [Jri/r, 



of the blood, during which the fibrin enveloping the colouring 

 substance presses out the serum. This method is indeed but 

 very imperfect, as a large portion of the serum still remains 

 attached to the red globules in the coagulum ; but it is the only 

 one that we can employ. 



I shall first consider the crassamentnm, and its two consti- 

 tuent parts, fibrin and colouring matter. 



The Chemical Properties of Fiirin. 



'Fibrin is insoluble in cold water. In boiling water it curls 

 up, and after the ebullition has continued some hours, the water 

 acquires a milky hue, but no gaseous product appears. By this 

 operation fi rin undergoes a species of decomposition ; the water 

 in which it is boiled affords, by the addition of tannin, a preci- 

 pitate of white and distinct flocculi, which cio not cohere I 

 ther by the heat, as those produced by gelatin. The evaporated 

 liquid does not gelatinize to whatever degree it may be concen- 

 trated, and leaves a white, dry, hard, and friable residue, which 

 is soluble in cold water, and has an agreeable taste similar to 

 fresh broth, and totally unlike the salt and acrid flavour of the 

 extract fioni muscles. Fibrin, by long boiling in water, loses its 

 property of softening and dissolving in acetic acid. 



2. In alcohol of specific gravity 0*81 fibrin undergoes a species 

 of decomposition, and forms an adipocirous matter, soluble in 

 alcohol, and precipitated by the addition of water ; having often 

 a very strong and unpleasant odour. The alcoholic solution 

 leaves on evaporation a fat residue, which did not pre-exist in 

 the fibrin, and which, as we shall find, is likewise formed by 

 the action of alcohol on the colouring matter and on the albumen. 

 Fibrin heated in alcohol retains its property of softening and 

 dissolving in acetic acid. 



3. By the action of ether fibrin is converted into an adipo- 

 cirous mass similar to the preceding, but id much greater 

 abundance, and having a much stronger and more disagreeable 

 odour. We are on this account precluded from employing 

 generally either alcohol or ether in analytical experiments on 

 animal substances. 



4. In concentrated a : brin becomes immediately 

 soft, transparent, and with the assistance of heat is converted 

 into a tremulous jelly. By adding water and warming it, this 

 jelly is completely dissolved, with the evolution of a small quan- 

 tity of azotic gas. The solution is colourless, of a mawkish and 

 slightly acid taste. During its evaporation a transparent mem- 

 brane appears on the surface, and after a certain degree of 

 approximation, the gelatinous substance is again re-produced: 

 but this gelatine has no resemblance to that formtd bj paste. 

 "When completely desiccated it is a transparent mass which 



