158 ARBOREAL MAN 



special tactile sense organs are lodged in the skin of this 

 region, and special tactile sensory hairs — the whiskers, 

 etc. — are connected with them. When a Shrew, nosing 

 its way about its habitat, comes across a novel object 

 it learns much of it by its smell; but by the multiple 

 stimuli imparted to the tactile sense organs, through the 

 whiskers of its elongated and mobile muzzle, it consider- 

 ably reinforces this knowledge, by adding an idea of 

 size, form, etc., of the object, the smell of which has been 

 tested. Snout-tactile, or fifth cranial nerve, impressions, 

 therefore, soon find their way to the pallium, and the 

 long muzzle becomes typical and emblematic of this 

 association in all primitive Mammals, Prototherian, 

 Metatherian, or Eutherian. 



In dealing with the story of the fore-limb, we have 

 seen what is the fate of this elongated snout in the evolu- 

 tion of the arboreal animals. With the emancipation of 

 the fore-limb, and the development of the power of hand- 

 grasp, there is seen harmonious recession of the snout 

 region, the grasping hand taking on the functions of the 

 grasping jaws. 



But there is something more important and far- 

 reaching than this in the process, for the grasping hand 

 becomes also the testing and touching hand. Not only 

 does the hand come to take over the crude grasping 

 functions of the teeth and jaws, but in gradual stages it 

 slowly but surely usurps the delicate tactile duties of 

 the muzzle. The recession of the snout is therefore a 

 vastly important thing, for not only are the characters 

 of the jaws and teeth and the general build of the face 

 profoundly altered, but the principal tactile organ of the 

 animal body is transferred, as a whole, from one part to 

 another. The liberated hand takes on the duties of the 

 snout, and the exchange is effected very completely and 

 harmoniously, so that all those functions formerly dis- 

 charged by the snout are now carried on, and with far 

 greater efficienc}-, by the hand. 



