104 MENTAL OPERATIONS IN EELATION TO TIME. 



vaguely, a line dividing the more mechanical functions 

 of the mind from that higher individuality, which is 

 conscious of itself in itself. But here again we are met 

 and entangled by the new doctrine of unconscious cere- 

 bration a perplexing phrase, yet not more perplexing 

 than the function it professes to describe. We admit, 

 and are arguing upon, that succession of mental states 

 which in their series form the individuality of our 

 being ; partly governed by the will, partly automatic 

 from habit or the influence of the external senses. But 

 this hypothesis, yet unproved, of ' unconscious cere- 

 bration ' supposes intellectual operations in which con- 

 sciousness has no part, but which nevertheless evolve 

 true logical results. It is difficult enough to interpret 

 the phenomena of sleep and dreaming. But here we 

 are called on to recognise an exclusion of mind from 

 the highest function of mind a stretch of metaphy- 

 sical paradox hard to admit, even while confessing our 

 ignorance as to those other relations of the simply 

 material and spiritual in our nature which no analysis 

 can reach. 



Eeverting now to our especial enquiry, we find 

 much to illustrate the value of the mode of research I 

 have sought to indicate. Take, for instance, the un- 

 doubted fact that the operations of some men's minds 

 are more rapid in logical sequences than those of 

 others. Such inequality has been shown to exist in the 

 time required for transmission to the sensorium of 

 actions on the organs of sense, and of volitions con- 

 veyed to the motor organs. The experiments of 

 Helmholtz and Du Bois Eaymond on the rate of tranx- 



