We must consider all the forces engaged in this struggle for mastery on the neck and chest of man, and remember on one hand the power of the normal slope of hair, the greater difficulty of altering the direction of the thick long hairs of monkeys and apes, and their relatively long resting hours; and on the other the shorter and finer hairs of man and the increasing efficiency of his platysma muscle in varied actions. Professor Keith mentions four functions of the platysma: that of _depressing the angle of the mouth and lower jaw, helping to flex the head upon the chest_, and to _empty the laryngeal air-sac_, and _protecting the deep parts of the neck when it is tense_--adding the significant comment that “it is usually active in temper”--I presume this to mean bad temper! Leaving out of account the emptying of the laryngeal air-sac, is it not evident that the remaining three actions of the platysma are very much more exerted in the case of man with all the numerous occupations and movements of his head and neck, in obedience to his higher brain, than in the apes, monkeys and lemurs, endowed with a fitful activity, with fewer and less variable movements of their head, and long, long hours spent in their particular form of meditation? So, when the muscular sheet, which, as I have said, is _closely attached to the skin of the chest and more loosely to that of the neck_, contracts and becomes shortened between its origin on the chest to its insertion in the face and jaw, it gives a most obvious pull on the skin over it and wrinkles it vertically in a manner which will strike any thin person who contracts it voluntarily before a looking-glass. The connection shown between the action of the platysma muscle and the change of hair is so close that it can hardly be questioned that one is the cause of the other. If it be not proved to demonstration it is “tremendously probable” and the connection falls into line with the previous demonstrated cases. I must add here a remark suggested by the views of man’s descent put forward since this was written. The claim that man has changed the direction of his hair on his back and chest by use and habit owing to altered modes of life is not dependent on the simian theory of his descent. The change to his present patterns on those two regions from those of any “active arboreal pioneer” among insectivores is just as striking and is open to the same line of explanation. It would serve no useful purpose here to travel further over the varied streams of hair on the body of man. CHAPTER XIV. MISCELLANEOUS EXAMPLES. In this chapter a few of the rarer examples of hair-clad mammals which present remarkable changes at critical areas of their hairy coats may be considered with advantage. I have chosen six, of which three appeared in my former book. The Giraffe.