25. This envelope appears to have upon the mucous surfaces the same texture as on the skin, excepting in the delicacy of the laminæ from which it is produced. It is to this delicacy, which gives more exposure to the nerves, that we must doubtless refer the facility with which we excite various remarkable modifications in the sensibility, when by the Galvanic process we apply zinc to the mucous surface of the conjunctiva, the pituitary membrane, the internal membrane of the rectum, or of the gums, &c., and bring these several metal plates into mediate or immediate contact. The epidermis when removed is quickly reproduced; being destitute of all kinds of sensibility, it in this respect serves the same purpose as the skin, by guarding the very sensible corps papillaire which is subjacent to it. To its presence over the mucous membranes we must attribute the ability they have of being exposed to the air, and even to the contact of foreign bodies, without excoriating or inflaming, as is seen in cases of artificial anus, prolapsus ani, &c., whilst serous and fibrous membranes never suffer such exposure with impunity. Hence there is no danger, in this respect, from opening the bladder: hence, on the contrary, that precept so justly recommended, not to open the cavity of the peritoneum, and to make the least possible incision into the synovial capsules. I would observe, that the existence of the epidermis upon mucous membranes is an important consideration, as respects the opinion of those who, like Séguin, believing them to be without it, have said, that contagion is always received by the lungs, and not by the skin, which is, according to them, defended by this envelope. 26. In the organization of the skin, immediately under the epidermis is placed the corpus mucosum, particularly described by Malpighi, and generally considered as the seat of colour in the different varieties of the human species. It is described as a coat, pierced with holes by the passage of the nervous papillæ: M. Sabattier points out the manner of demonstrating it. Sömmering has, it is said, seen it separated from the epidermis and chorion on the scrotum of an Ethiopian. I confess that I have not yet been able to perceive it: M. Portal does not appear to have been more fortunate.