THE PATTERNING OF SKILLED MOVEMENTS 1 68 1 



FIG. I . Left and upper right: Evo- 

 lution of the pattern of localiza- 

 tion in the postcentral tactile area 

 as defined in a series of mammals. 

 The dotted areas show the extent 

 of the areas devoted to hand and 

 foot. The figures are not all to 

 the same scale, but the propor- 

 tions of each are approximately 

 correct. [From Woolsey (136).] 

 Lower right: Motor sequences in 

 the Rolandic cortex of man 

 shown on a coronal section of the 

 hemisphere. The length of each 

 block line in the cortex indicates 

 the comparative extent of the 

 representation of movement of 

 each part aroused by electrical 

 stimulation of the corresponding 

 cortical area. The importance of 

 the hand, as shown in the homun- 

 culus, is to be noted. [From 

 Pcnfield & Rasmussen (96).] 



MARMOSET 



relation to the activities of prehension, the motor 

 centers of the face have kept an importance equal, at 

 least, to that of the hand. This fact is related to the 

 development of a new and unprecedented facial 

 function, the emission of organized sounds which 

 constitute the complex phonetic expression of man. 

 (Specialized motor areas also are associated with 

 the control of ocular movement in relation to the 

 perfecting of binocular vision.) 



One of the more significant outcomes of this evolu- 

 tion is the development of new nervous pathways 

 connecting the cortical centers of command with 

 the peripheral motor organs. The appearance fol- 

 lowed by the development and the perfecting of the 

 pyramidal system in the vertebrates (69) is directly 

 related to the refinement of control of the muscle 

 groups most used in the expression of skilled move- 

 ments. We shall come back later, and more ex- 

 tensively, to this point. 



This picture of phylogenetic evolution is confirmed, 

 on the whole, by the course of human ontogenesis ; 

 the progressive development from motor activities 



consisting of prehension and specifically buccal ex- 

 ploration to the ever more preponderant utilization 

 ol the hand, the potentialities of which are mani- 

 fested in strict relationship to the delayed and pro- 

 gressive maturation of the pyramidal system. 



In this ontogenetic evolution there likewise appears 

 a strict functional synergy uniting the system of pre- 

 hension with the system for securing information 

 (first cutaneous, then essentially visual) and with 

 the mechanism for locomotion with progressive 

 erection of the body's axis and the liberation of the 

 superior members by assumption of the standing 

 position. 



To this progress contributes, to an important 

 degree, the prodigious elaboration of human mental 

 activity. The human privilege of "motility of manu- 

 facture' undoubtedly depends, in part, upon the 

 mechanical advantages of the human hand and 

 upon the refinement of the nervous mechanisms of 

 command which evoke its action; but it is due, above 

 all, to the immense psychical possibilities of which 

 it is the slave and on which, in return, it confers 



