This thickness takes from the epidermis the transparency it has in the other parts; it is whitish and opake even on the hand and the foot. Thus the epidermis which, in negroes not being coloured, allows the blackness of the subjacent reticular texture to be seen, conceals in part this blackness in these places. I have observed however, by means of maceration, that the less deep colour of the soles of the feet and the palms of the hands depends also in this race upon this, that the reticular texture is really less coloured. We might say that every thing relates to animal sensibility in this region, the capillary net-work of which appears to be less, and in which all the phenomena that are derived from organic sensibility are much less active. In examining in this relation the hand and foot of a negro, I have been led to make upon the colour of the reticular body some other experiments, which form a short digression. 1st. By plunging into boiling water a piece of the dermis taken from any part it becomes twice as black, almost immediately; which is probably owing to this, that the fibres in approximating by the horny hardening, bring together the colouring particles, whence arises a deeper black. This phenomenon is very striking, when the piece plunged into the water is compared with one that has not been. 2d. Maceration for a month or two, sometimes removes the epidermis without the reticular body, the seat of colour, and sometimes detaches the whole together. 3d. Being immersed for some days in cold water produces no sensible effect. 4th. Long continued stewing hardly changes at all this colour, after the deep tinge that has been suddenly given to it. Only by scraping with a scalpel the external surface of the skin which is then reduced to a kind of gelatinous pulp, we easily detach the coloured reticular body from it, which however always remains adherent to a small portion of the chorion. 5th. Sulphuric acid, which reduces the skin like all the other organs to a kind of pulpy state, also enables us to remove this coloured portion easily, which is detached in separate pieces, but the shade of which is hardly altered at all. 6th. Nitric acid, though very much weakened, does not facilitate so much the removal of this coloured portion. It yellows the internal surface of the skin and the epidermis; but it has appeared to me to produce but very little effect upon the blackness of the reticular body. 7th. A portion of the skin of a negro, immersed for twenty-four hours in a solution of caustic potash, has not appeared to me to have undergone any alteration in its colour. I have made the same observation when I used a weaker solution. 8th. Putrefaction detaches the coloured portion of the skin, sometimes with the epidermis, sometimes alone, but it does not alter its colour. I have not employed other agents to ascertain the nature of this colour of the skin of negroes. Let us return to the epidermis, which we have for a moment lost sight of.