1816.] Membranous Bodies of Animals. 421 
its natural semi-transparence, and in a higher temperature it fused. 
It dissolved very speedily in a caustic ley. The boiled epidermis 
being distilled, gave out, like albumen, first a fetid ammoniacal 
liquid, then a yellow oil, much concrete salt, and the usual gaseous" 
products, without a trace of an acid. When allowed to putrefy, it 
exhibited the same appearances as albumen, to which in all its 
other properties it has the closest resemblance. 
(c) By incineration about 1 per cent. of a reddish ash was ob- 
tained, from which water dissolved a little potash, and sulphate, 
muriate, and phosphate, of potash. There remained behind a 
reddish residue, from which nitric acid dissolved a trace of phos- 
phate of lime. What remained consisted of gypsum, with traces 
of iron, and, as it seemed, of manganese. 
Chemists usually suppose, when they find no sulphate of potash 
among the salts obtained by the moist way, though it constitutes an 
ingredient of the ash, that this proves the presence of sulphur in 
the substance under examination, For my part, I am of opinion 
that to establish such a position much more accurate experiments 
would be requisite than have hitherto been made. In the present 
case it is easy to conceive that the presence of sulphate of potash in 
the ash is owing to the decomposition of gypsum. 
(d) On treating the epidermis with alcohol, at a temperature 
between 77° and 100°, only 4 per cent. of a fatty matter was dis- 
solved, which was precipitated by water, and separated by evapo- 
ration. 
A hundred parts of the epidermis of the human foot are, there- 
fore, composed of the following constituents :— 
Indurated albumen.......... ab cis wt g's oe eS tO, 95 
Mucus, with a trace of animal (gelatinous?) matter... 5 
Lactic acid 
Lactate of potash 
Phosphate of potash 
Muriate of potash 1 
Sulphate of lime eeereeeaseeoe @eeeaeetreaeses 
Ammoniacal salt 
Phosphate of lime 
Manganese? and iron 
MOGI SIE cre, nies eye, shefareidwysre.4? ik 
Olservations. 
From this analysis, it follows that Hatchett’s determination, that 
it consists of indurated albumen, is correct. It is very probable 
that the epidermis is formed from the lymph contained in the 
lymphatic vessels that pass through the skin. By strong friction, as 
takes place in several mechanical handicrafts, by much walking, 
&c, these vessels are probably ruptured in great numbers. Hence 
the great thickening of the cuticle which takes place in such cases. 
The fatty matter contained in the epidermis seems intended to 
4 
