CHEMICAL RESEARCHES ON THE ANIMAL FLUIDS. 187 



ments which have demonstrated its existence, and have there- 

 fore detailed minutely such researches as I have been enabled 

 to make upon the subject, hoping at some future period to ren- 

 der them more complete. 



The experiments to prove the nonexistence of gelatine in No gelatine in 

 the serum of blood will, I trust, be deemed sufficiently deci- l^lood. 

 sive : they show, that that abundant proximate principle of 

 animals is not merely separated from the blood, in which it has 

 been supposed to exist ready formed, but that it is an actual pro- It is a product 

 duct of secretion. ^ of secretion. 



The proportion of iron afforded by the incineration of seve- The blood 

 ral varieties of animal coal is much less considei-ab)e than we iht"e^iron "and 

 have been led to expect, and the experiments noticed in the this not pecu- 

 fifth section show, that it is not more abundant in the colouring '^' ^° 

 riiatter of the blood, than in the other substances which were 

 submitted to examination ; and that traces of it rxjay be dis- 

 covered in the chyle, which is white, in the serum, and in the 

 washed crassamentum or pure fibrina. 



The inferences to which I have alluded in the first section of The colouring 

 this paper are strongly sanctioned by these facts, and co- P"n^'!P'e of a 

 incide with the opinion, which has been laid before the Royal ture ; 

 Society by Dr. Wells*, respecting the peculiar nature of the 

 colouring principle of the blood, and support the arguments 

 which are there adduced. 



That the colouring matter of the blood is perfectly inde- independent 

 pendent of iron, is, I conceive, sufficiently evident from its ^^ ^'^°'^ ■ 

 general chemical habitudes, and it appears probable that it and probably 

 may prove more useful in the art of dying, than has hitherto |^^Y^.^^ "^^ " 

 been imagined, since neither the alkalis nor the acids (with 

 the exception of the nitric) have much tendency to alter its 

 hue. The readiness, too, with which its stains are removed 

 from substances to which no mordant has been applied, seem to 

 render it peculiarly fit for the purposes of the calico-printer. 

 I have not extended these experiments, nor have I had them 

 repeated on a sufficient scale to enable me to draw more ge- 

 neral conclusions respecting the possibility of applying them 

 with advantage in the arts : this would have led me into too 



* Phil. Trans. 1797. 



wide 



