COMPOUNDS OF ORGANIZATION. 63 
3. Fibrin.—This substance is usually procured for exa- 
mination, from blood or muscle. From the former it is 
obtained, by repeatedly washing the coagulated part which 
appears after blood drawn from an animal has been allowed 
to rest, until the water ceases to extract any thing soluble ; 
that which remains is the fibrin. Muscle yields this sub- 
stance after repeated macerations in water, the mass being 
frequently subjected to pressure, in order to expel the 
blood and other fluids from the pores. 
Fibrin is of a white colour, and soft and elastic, previous 
to its being dried. It powerfully resists putrefaction, and 
may be kept under water for a great length of time, with- 
out undergoing any change. It is insoluble in cold water. 
In boiling water, it curls up, and, after the ebullifion has 
ceased some hours, the water acquires a milky hue. A 
portion of the fibrin has been dissolved, which produces, 
by the addition of tannin, a precipitate of white flocculi. 
Strong alcohol and ether partially decompose it, converting 
it into an adipocirous matter. 
Acids dissolve fibrin directly, or alter its nature so as to 
render it soluble in boiling water. Acetic acid dissolves 
it entirely, and the solution has the appearance of jelly. 
With the alkalies, fibrin readily combines, and, according 
to Berzeius *, the compound bears no resemblance to 
soap. From the alkaline solution, the fibrin is thrown 
down in a more or less altered state by the addition of 
acids. 
When exposed to the destructive distillation, it curls up, 
then melts, gives out water, carbonate of ammonia, acetic 
and carbonic acids, a fetid oil, and carburetted hydrogen 
gas, indicating the presence of nearly the same ingredients 
as enter into the composition of albumen. The charcoal 

Annals of Phil. ii. p. 23. 
