The hair of man covers especially the cranium, some parts of the face, the front of the trunk, the genital organs, the extremities, &c. The quantity varies remarkably, as well as the form, length, &c. In order to form an accurate idea of it, we shall now consider it separately in the different organs, we shall then treat of its general organization, properties and development. ARTICLE FIRST. EXAMINATION OF THE PILOUS SYSTEM IN THE DIFFERENT REGIONS. This system must be considered on the head, the trunk and the extremities. I. _Pilous System of the Head._ The head is the part of the body in which this system predominates; it covers the whole cranium and defends it against the impression of external bodies, as the hairy coat of quadrupeds defends them. Thus this part is the least capable of exercising the sense of touch, either from the obscurity of the animal sensibility arising from this hairy covering, or because its convex form allows it to be in contact with external bodies only by a small surface. The face is less generally covered with hairs, though many are found upon it, especially in men. This part, in which in a very small space are collected the greatest number of our means of communication with external objects, viz. the organs of taste, smell, sight and even hearing, has but very little to do with the sense of touch, on account of its villous arrangement. Its form is also badly adapted to this sense. The mouth which is flattened cannot be applied to external bodies. Thus whilst the snout which is elongated in most quadrupeds, performs the double function of first feeling all bodies, turning them in various directions in order to ascertain their tangible qualities, and then of seizing them for nourishment, the mouth of man serves only for this last use; it is the hands which are destined for the first. Thus observe that all animals, even the most of those with clavicles, almost uniformly direct their snout towards the earth, whilst the mouth of man is naturally destined to an opposite position. _Of the Hairs of the Head._ They occupy upon the cranium all the space which corresponds with the occipital, parietal, the squamous portion of the temporal and a small portion of the frontal bones. Their limits do not vary on the sides; they always correspond above the ear. Behind, they sometimes go down upon the superior part of the neck; at others, they do not extend beyond the head. In applying blisters on the ligamentum nuchæ, we observe in this respect, almost as many varieties as there are subjects. We know how variable these limits are in front. Sometimes extended lower down, sometimes carried higher up, sometimes describing a curved line, and at others forming a real triangle the anterior point of which corresponds with the median line, they have really nothing constant.