1st. On the sole of the foot and the palm of the hand, we observe an infinite number of white fibres, shining like aponeurotic fibres, which are detached from this internal surface, form upon it a kind of new layer, cross each other in all directions, leave between them, especially towards the heel many spaces of different sizes, that are filled with fat, separate more and more, and are finally lost in the sub-cutaneous texture, nearly as the fibres of the brachial aponeurosis insensibly disappear in the neighbouring cellular texture. Hence why when we dissect the palmar and plantar integuments, we experience the greatest difficulty in separating them entirely from the cellular texture which is interlaced with these fibres; hence why also these surfaces have not, on the parts which they cover, the mobility which many others exhibit. The density of the cellular texture contributes also something to this arrangement which is essential to the functions of the foot and the hand, which are designed to seize and grasp external bodies. 2d. The dermis of the superior and inferior extremities of the back, of the neck, of the thorax, of the abdomen, of the face even and consequently of almost all the body, is distinguished from the preceding, because the fibres are much less distinct, and are not lost in the cellular texture by being as it were confounded with it, whence arises a remarkable laxity of the skin of these parts, and the very great facility with which it is dissected; in a word because the spaces between these fibres are much more narrow. These spaces appear like an infinite number of holes irregularly placed at the side of each other, containing most of them small fatty parcels of the neighbouring texture, and exhibiting, when these small parcels have been carefully removed, very evident vacuities. The fibres which form them, are sufficiently near each other, to make you believe at first view, that it is a surface pierced with an infinite number of holes, that has been applied under the skin. On the contrary, on the hand and the foot, towards the heel especially, it is a true net-work the spaces of which are larger than the fibres that form them; this is the reverse here. Be that as it may, these spaces in the internal surface of the chorion are very favourable to the action of tannin which penetrates the texture infinitely better from this side than from the opposite, because it insinuates itself into these numerous openings. I have had occasion to observe it in the human chorion which I have had tanned for the purpose. Chaptal has observed that the epidermis is a real obstacle to the action of tannin, and that on this account scraping is a preliminary operation essential to tanning, since it allows the skin to be penetrated on both sides; but even when thus scraped, it receives the tannin much more easily on the side of the flesh than on the opposite one.