352- PROTEIN-COMPOUNDS. 



loses these properties, while that of the arterial blood of the same 

 animal does not dissolve in a solution of nitrate of potash. In man 

 I found that fibrin, whether from venous, arterial, or inflammatory 

 blood, was soluble, excepting in two cases of inflammatory blood ; 

 the arterial and venous fibrin from pigs' blood dissolved equally 

 well, and with great rapidity in water containing nitrate of potash. 



Boiled fibrin possesses almost all the properties common to 

 coagulated albumen, from which it is extremely difficult to dis- 

 tinguish it. C. Schmidt* found the specific weight of dry fibrin 

 extracted with water, alcohol, and ether to be =1*2678 after de- 

 ducting the influence of the ash-constituents. The influence of 

 heat deprives this fibrin of the property of decomposing peroxide 

 of hydrogen, and of being converted into a soluble, albumen- 

 like substance by digestion in solutions of alkaline salts. With 

 acids and alkalies it reacts in the same manner as coagulated 

 albumen ; it dissolves in alkalies, and forms with them compounds 

 having no reaction on vegetable colours ; with acids it also forms 

 combinations which are insoluble in water to which an acid has 

 been added, but dissolve freely in pure water. Concentrated hydro- 

 chloric acid communicates an indigo-blue colour to it. By pro- 

 longed boiling in water, it becomes decomposed into a soluble and an 

 insoluble compound, to the former of which Mulderf has given the 

 name of teroxide, and to the latter, binoxide of protein. When 

 decomposed by chromic acid, or by peroxide of manganese and sul- 

 phuric acid, it yields a larger quantity of butyric acid than any of 

 the other protein- compounds or their derivatives; it yields, however, 

 less acetic and benzoic acid than albumen, although more than 

 gelatin (Guckelberger.J) 



Composition. Before we can consider the chemical constitution 

 of a body, it is always necessary to inquire whether we have to 

 deal with a pure and simple substance, with a chemical compound, 

 or, as is often the case, with a body with which several substances 

 are mixed. The question is more imperative in reference to fibrin 

 than to any other animal substance, for both microscopico-mechan - 

 ical investigations and many chemical experiments seem to indicate 

 that the ordinary, so-called purified fibrin is not a chemically 

 simple substance. Whether fibrin be separated from the blood 

 or from the lymph, it is invariably found to be mixed with hetero- 

 geneous morphological elements, especially with the colourless 



* Ann. d. Ch. u. Pharm. Bd. 61, S. 156-167. 

 t Ibid. Bd. 47, S. 300 328. 

 t Op. cit. 



