200 Ckemkal Properties of Animal Fluids; [Skpt. 



and the soluble animal substances belonging to that portion of 

 the serum which still adheres to the coagulum, and cannot be 

 entirely separated from it. The coagulum 1 have found, by one 

 analysis, to consist (exclusive of the saline and uncoagulable 

 ingredients) of 64 parts of colouring matter, and 36 parts of an 

 insoluble mixture of fibrin and albumen. 



Of' the Serum, Albumen, and Salts of the Bluod. 



When serum is heated in a glass vessel, over a water-bath, it 

 solidifies and forms a pearl-coloured jelly, transparent at the 

 edges. If it is stirred the coagulation is more uniform. It has 

 been said to blacken any silver instrument employed to stir it; 

 but this only happens when the scrum has begun to putrefy, or 

 when the bottom of the coagulum has been burnt. As this 

 blackening of silver is owing to sulphur, this substance has also 

 been reckoned among the constituent parts of blood. But it 

 would be equally proper to consider carbon and hydrogen as 

 constituent parts, since these enter into the composition of al- 

 bumen, in the same way as sulphur does. 



Muriatic acid coagulates serum. When heated, a small- 

 quantity of azotic gas is evolved. This coagulum has exactly the 

 same properties as the compound of fibrin and muriatic acid. 



The sulphuric and nitric acids also produce with the albu- 

 men of serum precisely the same compounds as with fibrin. 



Phosphoric acid does not coagulate serum. 



The acetic acid does not coagulate serum, and when this acid 

 is in sufficient quantity, it prevents the coagulation on heating. 



In short, the albumen of serum produces exactly the same 

 compounds with acids and alkalies as the fibrin does, and there- 

 fore to avoid repetition, I shall refer the reader back to my obser- 

 vations on this latter substance. The action of alcohol also is 

 perfectly similar in both cases. 



There appears therefore to be very little difference between 

 fibrin and albumen ; and the latter seems to be intermediate 

 between fibrin and the colouring matter. The only character 

 of distinction between fibrin and albumen is, that albumen does 

 not coagulate spontaneously, but requires a higher temperature 

 for that purpose. Coagulated albumen does indeed dissolve 

 more slowly than fibrin or colouring matter in acetic acid and 

 in ammonia, but probably this is owing to the influence of the 

 heat employed for its coagulation. 



Exper. I. — 1000 parts of serum evaporated to pei"fect dry- 

 ness, (that is to say, so as easily to be reduced to powder,) left 

 95 parts of a yellowish, semi-transparent mass, resembling am- 

 ber, that split to pieces in drying, which, in curling up, carried 

 with them thick scales of the porcelain glazing of the evaporat- 

 ing vessel. ^ 



