Edinger, Comparative Psychology. 445 



by imitating its cry with a metal mortar. Clearly, then, these ani- 

 mals hear very well that which concerns them. It has also been 

 shown by Pieper that in fishes, which according to all the accounts 

 hitherto given, appear so deaf, negative variation in the auditory 

 nerve is caused by the sounding of a tuning fork. How much work 

 has been done entirely in vain because we have not as yet fully ap- 

 preciated the fact that, in the absence of a mechanism for associa- 

 tion, nothing but the biologically adequate stimulus can bring about 

 movement! Why should a fish flee, as we have always hitherto 

 expected, at the sound of a bell or of a tuning fork ? Sounds of 

 that kind mean nothing to the animal unless — and I consider this 

 possible — it has been brought into relation with them by training. 



Thus we find ourselves compelled to divide sense stimuli into 

 those which are biologically adequate and those which operate only 

 by association. As one readily sees, here arise new problems for 

 investigation. But now we have reached the limit of the possi- 

 bilities of the palaeencephalon. 



I suspect that thus far in my address you have been under the 

 impression that what I have been presenting is not psychology 

 but physiology. I am entirely in accord with that, if we under- 

 take to draw sharply the line between psychology and physiology 

 upon the ground of our newly acquired anatomical knowledge. 

 No objection can be made if, not for all time, but tentatively, we 

 exclude all the above mentioned activities and also all instincts 

 from purely psychological consideration. As a knowledge of the 

 literature continually reminds me, the instincts hitherto have 

 rendered difficult a consideration of the truly psychological phe- 

 nomena of animals. In the literature — and one need think only 

 of what has been written about birds — they are continually 

 intruding to pervert our general views. This proposition to 

 regard the simple activities and the instincts of animals as sharply 

 separated from the other psychological processes, a proposition 

 to which I have been able to come only through a comparison of 

 the anatomy with the activities, is not a fundamental one but only 

 methodological. It will call forth your objection. But I hope 

 in the second part of this discussion, which will concern itself with 

 the neencephalon, to be able to show you that it is not so entirely 

 impracticable. 



The neencephalon, the bearer of the cortex, develops in the roof 

 of the brain, beginning as a rudiment which is evident even in the 



