Hence the index of the palm should be the proportion between the length of the palm itself and the length of the middle finger. This proportion is of importance because it has certain human characteristics; as a matter of fact, in the anthropoid apes the metacarpus is much longer than the fingers and the palm has a far lower index than that of man. In degenerates (thieves) the hand is frequently narrow and long.

The Proportions of the Fingers.—If the first and second articulations of the fingers are flexed, leaving the third extended, we find that the extremity of the middle finger reaches to the point where the thenar and hypothenar eminences (fleshy prominences at base of palm) are nearest to each other.

This basic point is only approximate and serves to tell us whether the middle finger is normal. The middle finger serves as a measure for the others, as follows:

It often happens that the development of the ulnar side of the hand—the little finger, or both little and ring finger together—is defective. Sometimes the little finger is not only extremely small, but a special malformation renders it shorter still when the hand is open; the second phalanx remains flexed, and cannot be extended. Combined with the shortness of such fingers there is also an extreme slenderness—cubital oligodactylia. It is a far rarer thing to find similar anomalies in the case of the index-finger. The thumb, on the contrary, is sometimes extremely short, in consequence of which it has slight opposability.

Functional Characteristics.—What characterises the functional action of the human hand is the opposability of the thumb. There ought to be a perfect movement of opposability of the thumb in respect to all the other fingers; but many imbecile children accomplish this movement imperfectly. The mobility of the thumb is associated with a group of muscles situated at its base which forms the great tenar eminence of the palm, opposite which, in corresponding relation to the little finger is the small hypothenar eminence. An insufficient development of these palmar eminences represents a serious malformation, which entails functional disturbances. The hand of the monkey is flat.

The Nails.—We have already seen that in the high type of hand the nails should be convex and long, and that in the low type, on the contrary, they are short and flat.

The normal nail should extend to an even level with the fingertip. Manual labour should normally serve the purpose of keeping the nails worn down; but we, who are not hand-labourers, must use the scissors, in order to maintain the normal state.

For, if they were not worn down, the nails would attain an enormous length, like the nails of certain kings of savage tribes, who as a badge of authority have such long nails that their hands are necessarily kept motionless; these kings must in consequence be waited on, even for the smallest need, and actually become the slaves of their own nails, which might be shattered by any sudden movement on the part of their royal possessor. Long nails, therefore, are a sign of idleness, while at the same time they demand a great deal of attention. Accordingly, let us repudiate the fashion of long nails.

As a form of anomaly, we sometimes meet with nails of such exaggerated length that they have the aspect of claws—onychogryposis; or, again, an almost total absence of nails, which are reduced to a narrow transverse strip—this characteristic is often found in idiots, and is aggravated by the fact that from childhood such persons have had the habit of "biting their nails."