Inquiry into the Nature and Properties of the Blood. 375 



surface ; consequently, its specific gravity differs very much in 

 different cases. The chemical properties of fibrin appear 

 exactly to resemble those of the muscular fibre ; being acted 

 upon in the same manner by nitric acid and the other re-agents, 

 so as fully to be entitled to the appellation of liquid flesh, as be- 

 stowed upon it by the older physiologists ; and the great re- 

 semblance between the muscular fibre and the sanguineous, 

 has led many to imagine that they are in fact identical. Al- 

 cohol ofsp.gr. "810 converts the muscular fibre into a kind 

 of adipocirous matter — into a substance partaking of the pro- 

 perties both of fat and of wax ; whilst this is more com- 

 pletely and perfectly effected by ether, yielding it in greater 

 abundance, and distinguished by a much more disagi'eeable 

 odour. It is converted by means of heated acetic acid into 

 a tremulous jelly, becoming immediately soft and transparent, 

 which jelly is dissolved by warm water, with the evolution of 

 a small quantity of azotic gas. Strong muriatic acid boiled on 

 fibrin, decomposes it, and produces a red or a violet-coloured 

 solution : digesting it with weak muriatic acid, it becomes 

 hard and shrivelled : this by repeated washing in water 

 changes at length into a gelatinous mass that is perfectly so- 

 luble in tepid watei". This solution reddens litmus paper, and 

 yields a precipitate with acids as well as with alkalies. Strong 

 sulphuric acid decomposes and carbonizes fibrin; diluted with 

 six times its weight of water and digested with fibrin, it ac- 

 quires a red colour, but dissolves scarcely any thing. The 

 undissolved portion is a compound of fibrin with an excess of 

 sulphuric acid ; and when this excess is removed by water, a 

 neutral combiiiation is obtained, which is soluble in water, and 

 has the same characters as the neutral compound of fibrin and 

 muriatic acid. 



Strong nitric acid at first disengages nitrogen or azotic gas 

 from fibrin, pure and unmixed with nitrous gas. By continu- 

 ing the digestion twenty-four hours, the fibrin is converted 

 into a pulverulent mass, of a pale citron colour, which when 

 placed on a filter and washed with a large quantity of water, 

 becomes of a deep orange colour. 



This yellow substance was discovered by Fourcroy and 

 Vauquelin, who gave it the name of yellow acid. Berzelius has 

 ascertained that it is a combination of the nitric and malic acids 

 with fibriu, which is in some degree altered by the process. 

 Fibrin precipitated from its solution in caustic alkali has 

 undergone some change by the solution; for it is now insoluble 

 in acetic acid. The changes that are wrought on the blood 

 by means of various other chemical substances, it would be 

 both prolix and useless to mention : what we have adduced 



