MUSCLES 203 



opportunities in the long history of mammalian evolution for 

 primitive forms to take a new course of life, and they have done so 

 on an extensive scale. The impulses that have led them may have 

 been started by some " needs " such as Lamarck taught, some 

 change in their surroundings involving new stimuli, or " insults," 

 as Haeckel called them, but the first of the structural stages must 

 have been in the cerebral cortex. 



Cross-Roads in Evolution. 



The most instructive levels of animal evolution are those where 

 two or more great stocks have diverged from a primitive one. There 

 may have been several factors leading to the division of the early 

 Ungulates into the odd-toed and even-toed groups, of the Carnivora 

 into cats, dogs and bears, the Felidse into the highly-specialised 

 genera of that intense famih', the early parting of gibbons from the 

 common anthropoid stem, and then the division of this line into 

 the three great genera with which we are familiar. Whatever may 

 have been the unknown factors in the environment such as changes 

 of climate and level, geographical isolation, increase of foes, pro- 

 fusion or lack of food, to which these diverging stocks became 

 adapted in their organs and form, in fact whatever we do not know, 

 we know this — that in their measure they acquired more convoluted 

 and often larger brains, and the stimuli passing through their 

 receptors into their consciousness increased with an evernowing 

 tide, in volume, intensity and complexity. Many an archaic habit 

 of their race they must unlearn, and it is doubtful if germinal 

 selection would avail in this valuable process of ecomomy as it is 

 held to do in the case of the human little toe. 



It may be taken as granted that increasing complexity of 

 brain in their own lines of life did accompany these adventurers 

 of small or large groups . It follows that muscular changes from the 

 original stock would follow neural changes, for movement and 

 activity is inseparable from the animal, and the integrating action 

 of the nervous system would constantly initiate, maintain and 

 establish fresh habits and these be expressed in new muscular 

 structure. Whatever higher uses, as we believe them to be, man 

 makes of his brain, as reflection, reasoning, imagination and associa- 

 tion, such were not the new properties acquired by these adventurers. 

 They were very much concerned with hunger and love, and for them 

 " philosophy " did not sustain the structure of their world. But 

 more varied movements of head, trunk and limbs, and greater 

 agility and strength brought them such prizes as were within their 

 reach. This may be only another way of expressing Sir E. Ray 



