Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them]

Chapter 34 On the Nails

[On the Usefulness of Fingernails]

In these two figures we represent the nail [unguis] as it is usually seen when it is pulled from a hand or foot that has been cooked for the preparation of a skeleton. The right 1 figure, marked with letters, shows the inner region of the nail, or its hollow; the other illustrates the convex [dorsal] side of the nail. 2 A shows the part 3 of the nail that appears before dissection. B marks the part 4 that is soft, is nowhere exposed, and should be considered as it were the root of the nail.

Why the digits have nails 5
The supreme Maker of things adorned the digits of the hands and feet with nails so as to have them attached as a support. The digits grasp only soft bodies with the fleshy parts that they have at their end. But objects that are hard and therefore resist the nature of flesh and forceably push it away, cannot be grasped without the aid of nails. For their flesh, which we shall later explain is a rather hard, fatty tissue spread beneath the skin, is then bent back and turned under, and for that reason needs reinforcement. Indeed, man gains numerous advantages from nails, if they are neither beyond the tips of the fingers nor below them, 6 as for example if it is necessary to scrape, scratch, pinch, peel, or pluck something.

The nature of nails is rightful 7
The supreme Maker of things fashioned the hardness of the nails 8 (which are also considered barriers against hurt and fracture) most justly. If they were harder than they now are, they would have been created like a bone and would in that case have been more suitable for prehension as being unable to be bent or turned back; but they would have been very easily broken, like other things of a hard and brittle composition. And so the Maker of things provided for safety as well as strength in making them moderately hard so as not to impair any function for which they were created, nor be damaged on any trivial occasion when with their softness

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they easily break the impact of things striking them from outside, like cartilages. For this same reason they have a convex surface because with this shape they are better disposed for resisting injuries.

Attachment of the nails
To keep them from hanging loose, 9 they are attached at their upper end by a ligament to the root of the last bone of the digits. Because it was worthwhile that they be attached to flesh and skin, skin surrounds the entire root externally, and internally flesh is attached throughout. 10 Galen attests that not only an artery and a vein but also a nerve extend into the very root, 11 and he writes that the nails take sense, life, and nourishment from these in the same way as other parts. 12 I know, indeed, that not only are two small nerves [Nn. medianus et ulnaris, Nn. digitales palmares proprii] (hand in fig. 2, ch. 11, Bk. 4) brought to the root of the nails, but also that they run with the veins [Vv. digitales palmares propriae] (figure of the hand, ch. 6, Bk. 3) beneath the nails, also to the end of the digit. I also believe that the nails lack all sensation. Therefore I agree in no small way with the view of those who think that the nails grow from a coalescence of bone, nerve, and skin (some add flesh as well). 13 But that veins, arteries, and nerves are not dispensed in the nails like garden channels is known from the fact that nails start out from a root and grow like hairs. It sufficed that these too are always being renewed like hairs, and since they are worn down daily they always admit growth, 14 which they acquire in length rather than width and depth. 15

Book One -- The things that sustain and support the entire body, and what braces and attaches them all. [the bones and the ligaments that interconnect them]