Chemical Composition of Human Blood. 119 



does not gelatinize after concentration and is precipitated 

 by nitrate of mercury and acetate and nitrate of lead*. 



This matter is supposed to give the specific flavour to 

 the flesh of different animals, and especially to the part 

 which forms the brown crust on roast meat. Thenard has 

 given it the name of osmazome. 



What remains from the fibrin loses all the characters of 

 this substance ; it no longer forms a jelly with acids or 

 alkalies and is insoluble in acetic acid. 



Dr. Rainy also found that when fibrin is dissolved in a 

 solution of common salt, the greater part coagulates by 

 heat, but there remains a minute portion of animal matter 

 in solution very similar to that which has just been noticed.f 



The manner in which acids and alkalies act upon fibrin, 

 would lead to the opinion that it performs the part of an 

 acid as well as a base. 



1. Strong sulphuric acid acts upon pure and dry fibrin, 

 which swells up into a yellow mass, absorbing the acid, but 

 not dissolving. During the action considerable heat is 

 evolved, which, when very great, according to Berzelius 

 assists in the mutual decomposition of the two bodies. 

 When this yellow substance is washed it becomes less 

 bulky, and is a neutral compound of fibrin and sulphuric 

 acid, as was noticed by Berzelius. 



2. Nitric acid changes the colour of the fibrin to yellow. 

 If the acid is strong the fibrin becomes of a lemon colour, 

 which does not dissolve in water but changes to an orange. 

 W^hen allowed to remain in the water for some time, with 

 a little heat, an oily looking substance appears on the sur- 

 face, which agrees with Dr. Thomson's observation that 

 fibrin is sometimes converted into fat by the action of 

 nitric acid. 



The yellow coloured mass Berzelius regards as a com- 

 pound of fibrin slightly altered and malic and nitric acids. 



3. Muriatic acid dissolves the fibrin and forms a fine 

 deep blue coloured solution, in which water produces a 

 white precipitate. This matter is a neutral compound of 

 muriatic acid and fibrin. 



4. The action of caustic soda upon the fibrin was per- 

 fectly similar to that of potash as observed by Berzelius. 



5. Besides the salts enumerated by Dr. Rainy, I found 



* Berzelius. t Records, vol. ii. p, 365. 



