350 PROTEIN-COMPOUNDS. 



the beginning, that is to say, the substance originally held in solu- 

 tion in the blood. We must, therefore, still limit ourselves to the 

 assertion that the blood of vertebrate animals holds a substance in 

 solution, which, by its metamorphosis, generates a substance not 

 soluble in the serum of the blood, and which we call fibrin. 



The view that formerly prevailed, namely, that the fibrin was 

 held in solution in the blood by alkalies and alkaline salts, and that 

 its coagulation was owing to the decomposition of the combination 

 of the fibrin and the alkali by the carbonic acid of the air, has been 

 thoroughly refuted by Nasse*; indeed, blood containing much 

 carbonic acid coagulates very slowly, and on the other hand, the 

 carbonated alkalies retard, and may even wholly prevent the coagu- 

 lation of the fibrin. If, therefore, we are determined upon seeking an 

 explanation of this phenomenon, we must rest satisfied with mere 

 fiction based upon analogy. Thus we may conceive that the 

 albumen of the blood, while undergoing a process of metamor- 

 phosis, is disposed to assume a metamorphosed and insoluble form 

 by the agency of the minutest quantity of oxygen, in the same 

 manner as the juice of the grape, according to Gay Lussac's expe- 

 riments, is brought into a condition of vinous fermentation by 

 means of the minutest quantity of oxygen. But when so distin- 

 guished an enquirer as Nasse, while* he declares this process to be 

 a chemical one, regards the substance that undergoes the metamor- 

 phosis, as endowed with vitality, we are bound to reject his expla- 

 nation as mere fiction ; for, independently of the fact that if a pro- 

 cess be chemical it must be capable of chemical explanation, it 

 seems to us wholly at variance with all preconceived ideas of life 

 to attribute life to a simple organic substance. 



Spontaneously coagulated fibrin is a yellowish, opaque, fibrous 

 mass, which becomes hard and brittle on drying ; it is without smell 

 or taste, and is insoluble in water, alcohol, and ether; after being 

 dried it merely swells in water, and becomes again soft and flexible ; 

 it readily decomposes peroxide of hydrogen ; it dissolves more easily 

 in acetic acid and alkalies than many other protein -compounds ; it 

 decomposes rapidly and putrifies in the air, dissolving, if sufficient 

 water be present, and becoming converted into a substance which, 

 like albumen, is coagulable by heat ; during this process it attracts 

 a considerable quantity of oxygen, gradually developes ammonia, 

 carbonic acid, butyric acid, and sulphuretted hydrogen, and leaves 

 a residue consisting principally of leucine and tyrosine (Scherer,f 

 * Handwbrterb. d. Physiol. Bd. 1, S. 109 ff. 

 t Ann. d. Ch. u. Pharm. Bd. 40, S. 35. 



