420 Chemical Analysis of some- [Junz, 
in a state of solution, they exhibit quite different properties, and 
are easily distinguished; but when they become insoluble, they do 
not appear to undergo merely a coagulation or condensation, but to 
assume quite different chemical properties. Several facts lead to 
the conclusion that fibrin contains the greatest proportion of azote ; 
that albumen follows next in this respect, while mucus contains the 
least. But as these differences are but small, it is difficult to render 
them sensible by analysis. This character seems likewise to be 
much influenced by the solvent; for hair, which, according to 
Vauquelin’s analysis, consists almost entirely of mucus, contains, 
however, not less azote than albumen does. ‘The phenomena 
which these bodies exhibit when they undergo spontaneous decom- 
position, their relation to different acids, and to water, the effects 
of a high temperature, of a dry distillation, &c. may afford marks 
of distinction to practised chemists; and these are the characters 
which I employ in my experiments. 
It is very much to be desired that chemists would prosecute this 
subject till accurate characters be ascertained by means of which 
these three substances may be distinguished from each other ; for 
the advantages resulting from such a discovery would not be con- 
fined to chemistry, but would extend likewise to physiology, as 
consequences might be drawn from it respecting the source of the 
formation of these matters. But I must not prosecute this subject 
any further, that I may not appear to deviate from the object which 
T have in view. 
I. Epidermis of the Foot. 
(a) When boiled in water, about five or six per cent. were dis- 
solved. When the concentrated solution was left in the tempera- _ 
ture of 77°, it dried to a yellowish, transparent, tough mass, in 
which a number of small crystals were visible, though they could 
not be separated. 
The concentrated solution acted as an aeid on litmus paper. On 
cooling, it gelatinized very imperfectly. It was precipitated by 
solutions of mercury, silver, lead, and oxalic acid. ‘Tincture of 
nutgalls occasioned scarcely any precipitate ; and barytes, ammonia, 
and alcohol, none at all. Lime caused a smell of ammonia to 
exhale. Hence it contains neither a sulphate nor phosphate of 
lime. An acid, a trace of gelatin, and mucus, were its principal 
ingredients. 
From the dried mass of the decoction alcohol dissolved, besides 
an uncombined acid, some salts, which separated in crystals. This 
acid possessed all the properties of the acid discovered by Scheele 
in milk, and afterwards by Berzelius in different animal substances, 
and known by the name of Jactic acid. 
(l) The portion of epidermis which is insoluble in water ap- 
peared, after the boiling, snow-white, and prodigiously swelled. 
It dissolved completely in nitric acid, and produced much oxalic 
acid. When heated, it dried to a very hard skin, which. possessed 
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