114 INITIATIVE IN EVOLUTION 



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. 



