CHAP, x.] OF THOUGHT. 439 



labour upon the general constitution, the difficulty there is in 

 being at once a man of action and a man of thought. 



It is evident that the psychometrical process which we have 

 just described is one of the most fortunate applications of physio- 

 logy to the study of the cerebral functions. This process will 

 surely be perfected and largely utilised, and we may predict 

 that it will bear yet more fruit. 



As we have already remarked, sensorial excitation at the 

 terminations of the sensitive nerves only provokes a rupture of 

 equilibrium, setting at liberty forces which counterbalance each 

 other. It is the spark which kindles the powder. Doubtless, 

 it is very hazardous to assert, with M. Wundt, that the sensation 

 grows like the logarithm of the excitation which produced it. 1 

 The facts of biology, with their diversity, their infinite variability, 

 are very ill adapted to the inflexibility of mathematical formulas. 

 But leaving logarithms aside, it is unquestionable that sensation 

 is not contained in the peripheric excitation, and that its 

 intensity increases more rapidly than that of the external cause 

 which has provoked it. 



Sensibility is, then, a property inherent in the nervous cell, and 

 the sensations, or to speak more generally, the facts of conscious- 

 ness, are phenomena which interpose between the afferent and 

 efferent currents of the reflex action, and which, once produced, 

 persist, have a kind of separate existence, can revivify, combine, 

 aggregate themselves to fresh impressions and sensations, are 

 awakened according to the impulsion of the desires, forming 

 finally a mental amalgam which constitutes the psychical indi- 

 viduality. But definitively, in spite of the extreme complication 

 of the mental microcosm, the muscular movements which follow 

 our volitions are only the last point of a reflex series, of which 

 the direct or indirect origin is always an excitation bearing upon 

 the extremities of the sensitive nerves. 



Surely this is one of the most important services rendered by 



1 Wundt, Menschen und ThierseeU (analysed by Th. Ribot, in the Revu* 

 Sdentifique, 1875, No. 31). 



