It is in the middle of this small cylindrical sac, of which I have just spoken, that the origin of the hair is found. We see at its extremity an enlargement oftentimes almost insensible, at others very evident, though always less than has been said. This enlargement is of the same colour and nature as the hair itself. It adheres to the canal very probably by the vessels and perhaps the nerves it receives from it. The hair which arises from it goes through its canal without adhering, as I have said, to its parietes, passes with it through the oblique pore of the dermis, leaves it at the epidermis, and goes outward. All authors say that the hair does not pierce the epidermis, but only raises it up, and that this forms a sheath which accompanies it to its extremity. This assertion is incorrect; in fact, 1st, the hair is as thick in its canal of origin as it is out of it. 2d. This canal being opened at its extremity opposite to the skin, we can draw out of it, as I have said, the whole hair with great ease, and without the least resistance; which would not be the case however if the covering of the epidermis was to be broken. It appears that from the enlargement of its extremity, the hair has no adhesion either in the sub-cutaneous canal, or in its passage through the skin, or the epidermis. 3d. If the cutaneous epidermis was raised up to cover the hair, this would have a treble thickness, unless this epidermis became wonderfully thin upon it. 4th. We do not see this pretended rising up by drawing out a hair of the head; on the contrary a depression exists at the place where this comes out. The cutaneous epidermis furnishes nothing then to the hairs, though the nature of them may be in part the same as its own, and it is proper to consider them as uniform in their structure from one extremity to the other. Under the skin, through it and out of it, the hair is composed of two distinct parts. One external, forms a canal which extends from the enlargement of the dermoid extremity to the opposite one; the other internal, which composes as it were the medulla of it, is of an unknown nature. II. _External Covering of the Hairs._