THE PHYSICAL BASIS OF MIND. 35 



this and that group of muscles into action. Much light is at 

 present being thrown upon this subject by the researches of 

 Hitzig, Eritsch, Ferrier, Goltz, and others ; but we must pass 

 on to consider that function of these great nerve-centres with 

 which we shall henceforth be exclusively concerned, the 

 function, namely, of being associated with the phenomena of 

 Mind. 



As the cerebral hemispheres pretty closely resemble in 

 their intimate structure ganglia in general, there can be no 

 reasonable doubt that the mode of their operation is substan- 

 tially the same ; and as such operation is here attended with 

 the phenomena of subjectivity, there can be equally little 

 doubt that such phenomena must constitute a sort of obverse 

 reflection of ganglionic action. Looking, then, upon this 

 obverse reflection, can we detect any fundamental principles 

 of mental operation which may reasonably be taken to corre- 

 spond with the fundamental principles of ganglionic opera- 

 tion? 



The most fundamental principle of mental operation is 

 that of memory, for this is the conditio sine qud non of all 

 mental life. But memory on its obverse side, or the side of 

 physiology, can only mean that a nervous discharge, having 

 once taken place along a certain route, leaves behind it a 

 molecular change, more or less permanent, such that when 

 another discharge afterwards proceeds along the same route, 

 it finds, as it were, the footprints of its predecessor. And 

 this, as we have seen, is no more than we find to be the case 

 with ganglionic action in general. Even long before move- 

 ments involving muscular co-ordination have been repeated 

 with sufficient frequency to become consolidated into one 



mixed and indissoluble act, they become, in virtue of the 

 principle which I have termed the principle of use, more and 

 more easy to repeat ; in all but in the absence of a mental 

 constituent the nerve-centre concerned remembers the pre- 

 vious occurrence of its own discharges: these discharges have 

 left behind them an impress upon the structure of the 

 ganglion just the same in kind as that which, when it has 

 taken place in the structure of the cerebral hemispheres, we 

 ■ni/e on its obverse side as an impress of memory. The 

 analogy is much too close to he attributed to accident, lor it 

 extends into all details. Tims, a ganglion may forget its 

 previous activity if too long an interval is allowed to elapse 



