290 PHY.SIOLOiiY OF MCSCLKS AM" NERVES. 



This sluggishness of the consciousness, if we inav so 

 call it, is exhibited in another way in certain experi- 

 ments instituted by Helmholz. The eve sees a figure, 

 \vhieli is immediately followed by a bright li.^'ht : the 

 more powerful the latter i<. the longer must the first 

 have been seen, if it is t> lie recognised at all; more- 

 over, complex figures require m..re time than simpler. 

 If letters are seen lighted up on a bright ground for a 

 very short time, no other light following, a shorter time 

 is necessary for the recognit ion, the larger are t he letters 

 and the brighter the illumination. 



It i> true that it is only very simple brain activities 

 the origin of which can be in any wav made dearer bv 

 such experiments as these; but yet these are the rudi- 

 ments of all mental activity -sensation, conception, re- 

 flect ion, and will; and even the most elaborate deduct ion 

 of a speculative philosopher can only be a chain of such 

 simple processes as those which we have been observ- 

 ing. These measurements, therefore, represent the 

 beginnings of an experimental physiological p>ycholo^\, 

 the de\elopment of which is to be expected in the 

 future. It seems to me that remunerative study of 

 the processes in nerve-cells must start from the very 

 simplest phenomena. Results are, then-lore, to be fir>( 

 looked for in the study of the processes of reflection : 

 possibly these will prepare the ground on which at some 

 future time a mechanism of the nervous pmco-es m; i V 

 be built. 'In truth; say- I ). !'. Strains, in 'The Old 

 and the Ne\v Faith/ ' lie who shall explain the gra-p 

 of the polyp after the prey which it has perceived, or 

 the Contraction of the insect lar\a \\heii pierced, will 

 indeed be yet far from having in this comprehended 

 human thought, but he will be on the way to do so, and 



