L. Manouvrier — Pithecanthropus erectus. 231 



superior member with reference to locomotion that the func- 

 tions of prehension and of manipulation of the hand have 

 been able to acquire adaptations the most varied. The per- 

 fecting of the tactile sense must have been an immediate 

 result of this emancipation. This result must have involved 

 the acquisition of a multitude of new notions suggesting new 

 movements, new actions. From that, the multiplication of the 

 movements of the lingers and of their combinations, the in- 

 crease in manual skill and all the psychologic consequences, 

 reacting the one upon the other, which must have been pro- 

 duced necessarily, by increase, in variety and complexity, of 

 newly acquired motive and sensorial representations. On this 

 subject, I could not do better than to refer the reader to the 

 beautiful pages devoted by Herbert Spencer to the parallelism 

 of the sensorial and motor improvement in the animal series 

 together with the intellectual improvement.* 



It is impossible to say, even approximately, to what augmen- 

 tation of cerebral weight the transformation in question may 

 correspond, but there are grounds for believing that this aug- 

 mentation must have been considerable, all the more so since 

 the intellectual growth in question must have influenced simul- 

 taneously the sensorial and motive manifestations, and the 

 order of sensations the psychologic importance of which is 

 extreme, and the order of movements (the movements of the 

 fingers) very numerous and which we know to be of great 

 help in the function of expression. This function is perhaps 

 the most important to be considered here, because its progress 

 reacts in a capital manner upon intellectual and social develop- 

 ment. It may have been noticed, among divers savage peoples, 

 how much the language by gesture makes up for the imperfec- 

 tions of the spoken language ; it is then allowable to suppose 

 that the movements of the hands and of the fingers figured 

 largely among the primitive means of expression of Pliocene 

 man. 



I do not believe it is possible to cite any ulterior cause of 

 psychologic progress and of increase in brain weight compara- 

 ble to the emancipation of the superior members with which . 

 we have just been occupied. The perfecting of articulate 

 language must have been consequently the principal factor 

 supervening in the psychologic and cerebral progress, to which 

 would be due the superiority of the lowest existing races over 

 the Pithecanthropus. 



The quantitative cerebral progression has been accompanied 

 by an improvement in the general form of the brain. This 

 improvement is already perceptible in the Pithecanthropus 

 according to the general form of the skull ; it seems, however, 



* H. Spencer, Principles of Psychology, vol. i. 



