68 PSYCHOLOGY. 



only one other published report of a similar experience.* It 

 would seem that in such a case the neural jDrocess corre- 

 sponding to the imagination must be the entire tract con- 

 cerned in the actual sensation, even down as far as the 

 retina. This leads to a new question to which we may 

 now turn — of what is 



THE NEURAL PROCESS "WHICH UNDERLIES IMAGINATION ? 



The commonly-received idea is that it is only a milder 

 degree of the same process which took place when the 

 thing now imagined was sensibly perceived. Professor 

 Bain writes: 



" Since a sensation in the first instance diffuses nerve-currents 

 through the interior of the brain outwards to the organs of expression 

 and movement, — the persistence of that sensation, after the outward 

 exciting cause is withdrawn, can be but a continuance of the same dif- 

 fusive currents, perhaps less intense, but not otherwise different. The 

 shock remaining in the ear and brain, after the sound of thunder, must 

 pass through the same circles, and operate in the same way as during 

 the actual sound. We can have no reason for believing that, in this 

 self-sustaining condition, the impression changes its seat, or passes into 

 some new circles that have the special property of retaining it. Every 

 part actuated after the shock must have been actuated by the shock, 

 only more powerfully. With this single difference of intensity, the mode 

 of existence of a sensation existing after the fact is essentially the same 

 as its mode of existence during the fact. , . . Now if this be the case 

 with irmpresslons persisting when the cause has ceased, what view are 

 we to adopt concerning impressions reproduced by mental causes alone, 

 or without the aid of the original, as in ordinary recollection ? What 

 is the manner of occupation of the brain with a resuscitated feeling of 

 resistance, a smell or a sound ? There is only one answer that seems 

 admissable. TJw renewed feeling occupies the very same parts, and in 

 the same manner, as the original feeling^ and no other parts, nor in 

 any other assignable manner. I imagine that if our present knowledge 

 of the brain had been present to the earliest speculators, this is the only 



* That of Dr. Ch. Fere in the Revue Philosophique, xx. 364. Johannes 

 MilUer's account of hypnagogic hallucinations floating before the eyes for 

 a few moments after these had been opened, seems to belong more to the 

 category of spontaneous hallucinations (see his Physiology, London, 1843, 

 p. 1394). It is impossible to tell whether the words in Wundt's Vorle- 

 Bungen, i. 387, refer to a personal experience of his own or not ; probably 

 not. II va sans dire that an inferior visualizer like myself can get no such 

 after-images. Nor have I as yet succeeded in getting report of any from 

 my students. 



