We have already seen that there is no correspondence between the functions of the various parts of the brain, so far as we yet know them and the overlying parts of the head to which phrenologists have assigned definite functions (p. 32). It is possible, however, that certain features of the head may be associated with definite mental tendencies. Every one of us has a difficulty in believing that intellectual ability can be associated with a receding forehead, yet the experience of daily life convinces most of us that the forehead is a most unreliable sign. Strongly marked eyebrow ridges are usually significant of energy and strength, and one can understand such an associationship, for beetling brows are usually a sign of muscular development. The chin is another feature which also seems significant of character; a man with a pronounced chin is usually also one of determination. The chin is sometimes defined as a character of man; rightly it should be regarded as a character of modern man. It has already been pointed out that the mandible is made up of two parts—a part for carrying the roots of the teeth—the alveolar part—and a part which forms the frame-work of the floor of the mouth. Now in primitive races the teeth are large and so is the alveolar part of the mandible; it actually projects beyond the chin, which is then said to be receding. If we supposed that the teeth were to become reduced in size and perhaps in number, and there are good grounds for supposing civilization has produced this effect, the alveolar part of the jaw will recede and leave the chin prominent. Hence the chin is never well marked in primitive races with large teeth and mouths—such as the natives of Australia, of Africa and of New Guinea. There is probably also a positive growth of the chin forwards in connexion with the muscles of the tongue and of the floor of the mouth. We thus see that a prominent chin marks as it were a step in evolution, and may indicate a special mental trait—such as determination.
We come now to deal with the hand, which has been exploited by one class of men as a guide to human character and extolled by another class as the most remarkable of man's characters. The hand is beyond doubt a very wonderful mechanism, but it is not necessary to remind the reader that the hand is only the passive instrument of that much more marvellous mechanism—the human brain. Professor Klaatsch is perfectly right when he maintains that the human hand is modelled on a most primitive and antique type. It retains the five digits of the earliest of mammals; even in some of the lowest of these the first digit is modified to a thumb. The anatomical differences between the hand of man and of the gorilla are really not great ones. As regards function, that is a different matter; the hand of the gorilla is heavy and clumsy because its chief function is to support the weight of the body during progression. In the chimpanzee and orang the palm and fingers are very long and narrow; they are capable of grasping and supporting the animal from the thickest branches. In man the hands have been set free from the purposes of locomotion and have become specialized as manipulative instruments. In swinging from branch to branch the anthropoids use their fingers as hooks ; their thumbs serve only for the minor purposes of grasping and lifting small objects. Hence in all the great anthropoids the thumbs are small; in the orang they are so reduced that one may say that they are vestigial. The nail is often absent from the thumb of the orang so small is the last phalanx or joint. The great size of the human thumb will be apparent when it is contrasted with the middle digit. In man it usually measures 68 to 70 per cent, of the length of the middle digit; in the gorilla, which has the most human-like hand, it is equal to 43 per cent, of the length of the middle digit. The thumb of man is characterized by its highly developed musculature. The special flexor or bender of the thumb is a large and distinct muscle; in anthropoids it is so reduced as to be almost a vestige; in the gibbon it is also large but it is conjoined with the flexor of the index finger. In man the great flexor of the thumb is undergoing a progressive change; in the great anthropoids a retrogressive one.
There is also a new extensor muscle on the human thumb. There are three segments for the thumb, each of which has an extensor muscle in man. In all apes the middle segment has no extensor, with one important exception. In a small proportion of gorillas we find the rudiment of such a muscle; it is being evolved as a slip which is separating off from the extensor muscle of the segment or joint at the base of the thumb. The human hand then has in a recent state of evolution undergone certain changes, especially as regards the size and strength of the thumb, but in its essential design and in the number of its parts it is really a very old structure. A vestige of a former bone is seen in the wrist of man. Between the upper and lower rows of carpal bones of the wrists there is seen a central bone in the wrists of monkeys. The central bone is also present in the orang and it appears during the development of the human hand but it soon disappears. Traces of it can be frequently seen. A similar fate has overtaken this bone in gorillas and chimpanzees.
The long and narrow hand is often regarded as showing breeding when it occurs in mankind ; we have seen that the orang and chimpanzee have hands of this nature. When, too, we come to study the lines of the palm—the lines to which astrological names have been applied since ancient days—we find that man is not peculiar. When the thumb is flexed on the palm a fold appears between the ball of the thumb and the rest of the palm ; the crease which marks the site of the fold is known as the " line of life." If the thumb and little finger are brought in contact, another fold appears on the centre of the palm running from the wrist towards the base of the middle finger ; it is the " line of Fate." When the fingers are flexed two folds appear across the palm ; the one nearest the base of the ringers is the " line of the Heart; " the further transverse line is that of the " Head ; " both it will be observed are foldings of the skin of the palm in front of the knuckle joints. These creases or lines in the skin are exactly of the same nature as the folds which appear in front of the elbows and behind the knees in the sleeves and trousers of the sedentary student. They indicate the manner in which the thumb and fingers are flexed on the palm. Palmistry is really a childish game of make-believe. It must not be forgotten that monkeys which we count quite low in the primate scale have the " girdle of Venus " —and well marked " marriage lines " ; the lines of our hands are old-time hieroglyphics. Those on the soles of our feet are also interesting. They are arranged in a similar manner to those of the palm, but only vestiges of them are left on the human feet at birth owing to the great modification which man's foot has passed through, to make it suitable as an instrument of plantigrade progression.
We have already seen that the lines of the palm of the hand are formed exactly where the skin and tissues are folded when the fingers are flexed and when an object such as a cricket ball is grasped. The lines appear on the palm of the hand of the foetus, exactly right in position and direction, before hand movements have actually occurred. That is a very remarkable fact. It could be explained if we suppose that such folds were first produced by use and in course of time such adaptations have become inherited. What are the means by which such functional characters become inherited ? The foetus in which we see those lines on the palm has already the ova or spermatozoa set aside for another generation; we cannot conceive a means by which the movements of the hand can influence the ova which are to give rise to the next generation The manner in which acquired characters become hereditary is a great and unexplained puzzle. We must believe, however, that under certain circumstances " acquired " characters are inherited, otherwise how shall we explain the appearance of the flexion lines on the palm before the hand is actually in use ?
If we cannot use the lines of the palm as guides to the future we can certainly establish the identity of an individual from the patterns made by the papilla; on the finger-tips. The papillae of the palm and flexor surfaces of the fingers are prominent and arranged in lines with the furrows between the lines. As Professor Hepburn has shown, the papillae and furrows are designed to give security of grasp. On the summit of each papilla opens the duct of a sweat gland to keep the skin moist and so prevent objects from slipping from the grasp. On the fleshy bulbous end of each digit it will be seen that the rows of papillae form definite patterns. There are three common forms (1) a loop, (2) an arch, (3) a spiral or whorl. Forms are also seen in which these three types are more or less combined. If the reader will glance at his fingers, examining the digits from thumb to little finger, first of the right hand, then of the left, examples of all three forms will probably be observed, but he will not find anywhere in the world another individual who shows these forms occurring in exactly the same sequence. The patterns can be used as letters of an alphabet, and any one who has left his finger prints has left an unmistakable signature behind him. I look on my own fingers and see that the patterns come in the following order:—
Fore- Middle- Ring- Little-Thumb, finger. finger, finger, finger. Right Hand loop. arch. loop. loop. loop. Left Hand loop. arch, loop. loop, loop.
On the fingers of anthropoids the whorl is the predominant type, while in monkeys the patterns are of an oval and more primitive form.
On the palm of the human hand remnants of certain primitive patterns may be seen. One of these is situated on the hypo-thenar eminence—the elevation on the palm opposite the ball of the thumb. Traces of three patterns may be found on the palm at the roots of the fingers. These patterns on the palm are traces of certain elevations or pads which are well seen in the palm of the monkey's hand.