156 THE BLOOD. 



Fibrin is inodorous and tasteless, whitish, insoluble in alcohol 

 and acids, slightly soluble in boiling water long applied; coagu- 

 lates, as already said, when separated from the body ; dries hard, 

 brittle, and semitransparent. 



Albumen is inodorous, tasteless, colourless, soluble in water, 

 and coagulates by a temperature of 150, by pure potass, the 

 mineral acids, tannin, and many metallic salts, especially by bi- 

 chloride of mercury, and by prussiate of potass if a little dilute 

 acid is previously mixed with it. Acetic and some other acids 

 dissolve it, and even render it to a certain point soluble in alco- 

 hol and boiling water, according to M.Raspail; who also, under 

 the microscope, discovers albumen to consist of two substances, 

 the one an insoluble and organised tissue, the other a fluid con- 

 tained in the cells of this, y The insoluble portion, however, 

 forms gradually only, and in fresh eggs can scarcely be distin- 

 guished from the soluble; just as is the case with the woody 

 fibres of vegetables, that gradually form from a gum. Dr. Wol- 

 laston stated, that the soda of albumen prevents it from all coagu- 

 lating by heat, and the addition of an acid, by neutralizing the 

 alcali, renders it completely coagulable. 2 Raspail says*, " alcaline 

 solutions, even alcaline carbonates," prevent heat from coagulat- 

 ing albumen. Mr. Brande thinks it liquid only through alcali. b 



Chemists all allow that fibrin, albumen, and colouring matter 

 afford, on decomposition, the same saline and gaseous products. 

 Berzelius views them all three as modifications of the same sub- 

 stance. Albumen contains a greater proportion of oxygen than 

 fibrin, and has sulphur for a constituent part, which, however, 

 cannot be detected while the albumen is entire, any more than 

 the iron while the cruor is entire. The chief differences between 

 the colouring matter and fibrin are, colour ; the spontaneous co- 

 agulation of fibrin at all temperatures, while the colouring matter 

 may be dried without losing its solubility in water and becomes 

 insoluble only at a certain temperature ; and the peculiarity in 

 the latter of not diminishing in volume like fibrin during exsic- 

 cation. According to most chemists, albumen is intermediate 

 between the two ; and its only character of distinction from fibrin 

 is, that it does not coagulate spontaneously, but requires a high 

 temperature or some chemical agent. M. Raspail maintains that 

 albumen and fibrin are identical; and that the slight differences 



y Hewson, 1. c. p. 191. sqq. z Ph. Tr. 1811. 



*^Hewson, 1. c. p. 198. b P/i. Tr. 1809. 



