This arrangement of cells into scarf skin has much to do with the healing of wounds. In cases of old sores that refuse to heal, or where the skin has been extensively destroyed, the doctors have found that good, healthy skin may be grafted upon the sores in such a manner as to invigorate and perfect the process of healing. Small particles of fresh skin taken from a healthy subject or from some other part of the patient’s body are placed upon the sore, the portions used being about the size of a small pinhead, and new life seems transplanted in the deadened part. The skin of a black man grafted upon that of a white man shows afterwards no trace of its origin, but becomes the same shade as that which it adjoins. Several animals change their tints to correspond with their surroundings. This subject has been exaggerated by observers of an imaginative turn of mind, but the fact remains that there is a decided change in the coloring of certain crabs and shrimps as well, as in soles, chameleons, tree-frogs, and two kinds of horned toads wherever they are found against any well-defined shade or color, Some have maintained that man takes on a tint somewhat resembling the soil of the territory where he abides in an uncivilized condition, but Beddard considers Schweinfurth’s statement that the Bongos have a reddish-brown skin similar to the soil of their country, and the Dinhas, their neighbors, are as black as their alluvial ground, merely as an account of what is purely accidental in the instances given. The coloring of most fish so that they cannot readily be seen by looking down into the water because of the blackness of their backs, is highly protective. And the fact is more apparent when we note that an enemy looking at the same fish from below is hindered in discovery because the white under parts of the fish are hard to distinguish against the light of the sky above. Nearly all the protective color markings of animals are modifications of the scarf skin. The true skin is of great interest both because it is the seat of what is called the sense of touch and because it is used so extensively in the arts in the form of leather.

Nerves of sensation expand over the whole surface of the body, and their minute branchings in the skin make contact with other substances highly discernible. But the sense of touch is peculiarly developed in few of the lower animals, and we may almost regard it as an attribute of man alone. Our ability to turn our fingers about things and move our hands over their surface gives us a power that is rare in nature. We can tell whether things are hot or cold, rough or smooth, sharp or blunt, wet or dry, and gather many other items of interest which the other senses are incapable of compassing. A monkey can wind his tail about a nut and tell by the sense of touch whether it is worth his while to crack it. The elephant moves the tips of his trunk carefully over the surface of what he wishes to examine and gets knowledge, he can depend upon. But it is the hand of man that shows the highest order of development of touch. By it blind men know their friends and read their books, bank clerks detect the qualities of the notes they handle, and a thousand deft acts in the arts are accomplished. The true skin is covered with minute projections called papillae. They may be traced in the palm by the ridges of the scarf skin. They are arranged there in rows so that while the naked eye does not discern the projections individually the rows of them may be noticed on the surface of the scarf skin. Some of these papillae contain blood vessels and others corpuscles of touch. Some papillae are small and simple, others compound. In one square inch of the palm have been counted 8,100 compound and 20,000 smaller papillae arranged in regular rows. There seem to be different end organs for different sensations. There are different spots which may be touched with a fine pointed pencil of copper which is quite hot and no feeling will result. Perhaps the same identical spots touched by the same point, after having been immersed in ice water, will give sensations of cold. Hot spots and cold spots maybe found and marked upon the skin. There are more hot spots than cold ones. Either of these when disturbed electrically will give sensations of heat or cold when neither heat nor cold is applied.