294 Journal of Comparative Neurology. 



equivalents, etc.). If we admit that practically every sensory- 

 motor reaction, even the most complicated one, can be uncon- 

 scious-automatic, under certain conditions mentioned, we con- 

 clude that a further mechanism of differentiation and associa- 

 tion must enter into activity to allow the quality ' psychical ' 

 to come in as an additional biological phenomenon. These 

 may be arranged all over the cortex, after the type of the 

 ground-bundles for the real segments of the neural tube, or 

 more definitely, in part at least, as Flechsig suggests by his 

 association-centers. This point can certainly not be called 

 settled now. Flechsig's data do not with necessity point in the 

 direction of his interpretation. It is to be hoped though, that, 

 by exclusions, we shall learn with sufficient accuracy which 

 cells belong to the ' psychical ' mechanism before the above 

 positive experiment can be looked for). 



In an analysis of the anatomical and physiological data we 

 must avail ourselves of the biology of the cell, but not forget 

 in doing so the whole organism. We do well to bear this in 

 mind when we speak of neural mechanisms. We do not use 

 the word mechanism in the sense of mechanics, but work with 

 biological factors. 



A biological entity, animal or plant, would roughly speak- 

 ing show us two sides of life, vegetative and reactive. The 

 two cannot be separated absolutely ; but we can speak of these 

 two sides or aspects, both of the organisms as a whole and of 

 the individual cells at each moment. This is best illustrated by 

 the following criticism of the reflex-arc. In most text-books 

 the reflex-arc is represented by the following elements : (i) The 

 afferent neurone, and (2) the efferent neurone in connection with 

 a muscle. It seems more true to biology and to our actual 

 knowledge of the nervous system, though, to think of the fol- 

 lowing points in a reflex, illustrated in the description of the seg- 

 ments: Suppose that it is possible to irritate one isolated sensory 

 nerve-element, although the interlacing of the terminations in 

 the skin would almost preclude even this. Assuming then, that 

 we can stimulate one afferent neurone independently by a prick 

 of the sole, we find that this cell sends many collaterals to sev- 



