It is for the same reason, that though these pores may be very evident, as I have said, in a separate portion of epidermis when examined against the light, this portion will support mercury, without giving passage to its particles. 6th. Most of the preceding means, which produce their effect only by an alteration of the vital forces, have no effect in raising the epidermis in the dead body. Putrefaction, maceration and ebullition are those by which it is effected. All act by breaking the elongations which extend from the dermis to the epidermis, though the mechanism of this rupture is not exactly known. II. _Organization, Composition, &c._ Authors have made many conjectures upon the structure of the epidermis, which it would be useless to relate here. I shall only speak of what accurate observation demonstrates. Its thickness is in general very uniform in all the parts. It has not appeared to me to be increased or diminished, according to the varieties of thickness of the skin on the back, the abdomen, the extremities, &c. It is only on the soles of the feet, the palms of the hands and the corresponding face of the fingers, that this thickness becomes greater. It is even so great in these places, that there is no proportion between them and the other parts of the body as it respects this membrane; it is especially towards the heel that it exhibits this character. This excessive thickness appears to be owing to different layers which are applied upon each other, and which seem to be superadded to the layer of the ordinary epidermis; but there is also a real difference, though but little known, in the organization; for example, when the epidermis has been removed from these parts by maceration, we cannot see, as in the others, those small appendices or inequalities regularly scattered over it, and which are the remains of the broken exhalants. In these places these vessels are torn smoother on the internal surface of the epidermis, on which are seen only the traces of the wrinkles of which we have spoken. I attribute to this excessive thickness of the epidermis of the soles of the feet and the palms of the hands, the difficulty and oftentimes impossibility of making blisters act in these places, on which I have often applied them there, because I thought that the sensibility being greater, they would produce more effect in some diseases. The failure of my attempts has compelled me to renounce them.