228 SYMBIOSIS 



It is worth noting here what the author avers with regard to 

 what the arboreal life has done for the respiratory system of the 

 Primate stock : 



it has given them flat chests and flat backs, has brought about a greater 

 degree of dependence upon the diaphragm as a mechanism of inspiration, 

 and at the same time, has added to the mobile fore-limb an increased source 

 of mobility in the muscles of the external respiratory system. 



There is, therefore, ample compensation for the vicarious 

 sacrifice of mobility on the part of the hind-limb. The com- 

 pensatory advantage more than balances the loss, seeing that the 

 evolution of the species generally is favourably determined by the 

 sacrifice. 



The recession of the snout is correlated with the liberation of 

 the hand, and 



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 discharged by the snout, are now carried on, and with far greater 

 efficiency, by the hand. The physical changes are great and obvious, 

 but as possibilities of progress in evolution they are trivial, compared 

 with the new avenues opened up for cerebral development. 



And the author continues thus : 



The enormous difference which the translation of the receptive mechan- 

 ism for touch impressions makes in animal economy is difficult to appre- 

 ciate. Change of conduct, however, makes apparent the more striking 

 lines of progress. The picture of the lowly animal which noses its way 

 through life smelling with its nose, and examining with its snout all novel 

 objects with which it comes in contact, is familiar to everyone, and is one 

 that contrasts strongly with the behaviour of an animal that has become 

 arboreal. Although it is a very long step to take, much may be learned 

 by going straight to a Lemur and watching its treatment of novel objects. 

 Here, handling obviously takes the place of nosing, although the scent 

 test is by no means omitted, especially in all cases where the suitability 

 of the object as an article of food is concerned. If Nycticebus is given 

 some fruit which is new to it, it will hold it to its nose. It will also smell 

 its hands, and if these tests produce no result, some animals will proceed 

 to rub the fruit, or hammer it on the ground, in order to obtain the scent 

 from a bruised or scraped surface. All this is done before any attempt 

 is made to eat any unfamiliar object. Much the same behaviour is shown 

 when the animal tests an object which is merely a novelty, and is not regarded 

 as a possible article of food. The superiority of hand-tactile information 

 is at once seen by watching such an animal, and the possibilities of 

 education of this new touch organ are easily realised. Even before the 

 power of grasp is developed, we may imagine the dawn stages of educa- 

 tional advances initiated by hand touch. 



The picture drawn, in reality reveals the road to mental 



