The drawings will help you to understand the relation of the nails to the cuticle and the cutis. In the upper of the three (fig. 75) the nail with the cuticle has been detached from the cutis, so that the continuity of the two, at either end, is shown. In the middle one (fig. 76) it is represented lying in its bed in the cutis; its thin hinder edge being received into a furrow made for it in the cutis. The layer of rete mucosum (_b_) extends behind and beneath it, between it (_d_) and the cutis (_c_), and continually adds fresh material to the nail, just as, in other parts, it adds to the substance of the cuticle. The cuticle, or white line (_a_) is continuous with the nail at the sides as well as at either end. The lower figure (77) shows the bed of the cutis in which the nail reposes, the nail as well as the adjacent cuticle and the rete having been cleared away. Thus the addition from the rete--in other words the growth of the nail--takes place at the hinder edge and at the under surface. In consequence of the addition from _behind_ the nail is increased in length and is pushed forward; and as it advances forwards it receives accessions from _beneath_, which increase its thickness and strength. Unless they be cut, or worn down, the nails grow to an indefinite length; and, when they extend beyond the tips of the fingers, their edges are bent in towards each other, and they become curved like claws. This tendency to a convex form is shown also if the nails be not properly supported by the pulps of the fingers. For instance, when persons become emaciated the pulps of the fingers usually participate in the general wasting and the nails become curved. Hence this shape of the nails has been regarded as an indication of consumption. You will understand, however, from what I have said that it is not really a symptom of any one particular disease. It simply indicates that, from some cause or other, the nutrition of the body is not properly maintained. The Dervishes in some parts of Asia allow the thumb-nail to grow long, and then pare it to a point, so as to be able to write with it. Dr Wolff, the Eastern traveller, has told me that he has repeatedly seen this done, and that he has in his possession manuscripts written in this way. [Illustration: Fig. 78. Transverse section of Nail Rete and Cutis.] Beneath the nail the cutis is disposed in a series of parallel ridges (fig. 78) with intervening furrows. These take the same direction as the nail, and, indeed, give rise to the fine lines that you see upon the surface of the nail. The rete mucosum, or deep soft layer of the nail, extends into the furrows between the ridges, just as the soft stratum of the cuticle extends between the papillæ of the cutis. It thus serves to keep the nail steady in its place, while it permits a certain amount of movement, and allows the nail to slide forwards upon the skin under the pressure caused by the growth at its hinder edge.