266 THE GROWTH OF THE BRAIN. 



legs in climbing. In man this control is not exercised, 

 and therefore there is no corresponding development, 

 yet it is by no means easy to say what the increase in 

 the latent areas may signify. From what is known of 

 the human brain it is justifiable to consider this pecu- 

 liarity as a mark of superiority. It appears, therefore, 

 that the development of the human cortex is not, as 

 might perhaps have been anticipated from the study of 

 the lower mammals, dependent on an increasing localisa- 

 tion, whereby larger and larger portions of the cortex 

 were given over to the efferent control of the different 

 groups of muscles, but to a limitation of the areas from 

 which the efferent impulse can be aroused. Possibly 

 the failure to obtain a response from so much of the 

 human cortex is related to the larger development of 

 the central elements having an associative function, 

 about the several groups of efferent elements, the 

 artificial stimulus being therefore applied to but a 

 fraction of the central elements usually concerned 

 in the discharge of the efferent group. This view 

 has been recently expressed by Flechsig. 1 More- 

 over, a distinction can fairly be made between mus- 

 cular reactions like those of facial expression, which are 

 in themselves highly variable, and the habitual move- 

 ments of the leg which, though not so variable in itself, 

 may yet occur in almost any combination with other 

 movements. It is hardly to be expected that the 

 cortical arrangement would in these two cases be similar. 

 Thus far attention has been directed to the efferent 

 cortical discharge which would occur in consequence of 

 incoming impulses directly arriving in the immediate 

 neighbourhood of the efferent cells. At the same time, 

 it is recognised that impressions received through the 

 ear can influence, let us say, the movements of the 

 1 Flechsig, Nenrolog. Centralblatt, No. 19, 1894. 



