FUNCTIONS OF THE BRAIN. 79 



All nervous centres have then in the first instance one 

 essential function, that of 'intelligent' action. Thej feel, 

 prefer one thing to another, and have 'ends.' Like all 

 other organs, however, they evolve from ancestor to descend- 

 ant, and their evolution takes two directions, the lower 

 centres passing downwards into more unhesitating autom- 

 atism, and the higher ones upwards into larger intellectu- 

 ality.* Thus it may happen that those functions which 

 can safely grow uniform and fatal become least accompanied 

 hj mind, and that their organ, the spinal cord, becomes a 

 more and more soulless machine; whilst on the contrary 

 those functions which it benefits the animal to have adapted 

 to delicate en\droning variations pass more and more to the 

 hemispheres, whose anatomical structure and attendant 

 ■consciousness grow more and more elaborate as zoological 

 evolution proceeds. In this way it might come about that 

 in man and the monkeys the basal ganglia should do fewer 

 things by themselves than they can do in dogs, fewer in dogs 

 than in rabbits, fewer in rabbits than in hawks,f fewer in 

 Lawks than in pigeons, fewer in j^igeons than in frogs, fewer 

 in frogs than in fishes, and that the hemispheres should 

 correspondingly do more. This j)assage of functions for- 

 ward to the ever-enlarging hemispheres would be itself one 

 of the evolutive changes, to be explained Hke the develop- 

 ment of the hemispheres themselves, either by fortunate 

 variation or by inherited effects of use. The reflexes, on 

 this view, upon which the education of our human hemi- 

 spheres depends, would not be due to the basal ganglia 



short span of life does not give it time to learn the new tricks asked for. 

 But Rosenthal (Biologisches Ceutralblatt, vol. iv. p. 247) and Mendelssohn 

 (Berlin Akad. Sitzungsberichte, 1885, p. 107) in their investigations on the 

 eimple reflexes of the frog's cord, show that there is some adaptation to new 

 conditions, inasmuch as when usual paths of conduction are interrupted by 

 a cut, new paths are taken. According to Rosenthal, these grow more 

 pervious (i.e. require a smaller stimulus) in proportion as they are more 

 often traversed. 



* Whether this evolution takes place through the inheritance of habits 

 acquired, or through the preservation of lucky variations, is an alternative 

 which we need not discuss here. We shall consider it in the last chapter 

 in the book. For our present purpose the modus operandi of the evolution 

 makes no difference, provided it be admitted to occur. 



f See Schrader's Observations, loc. cit. 



