288 VESTIGES OF GANGLIONIC IMPRESSIONS. 



As respects subjective or registered impressions, a few remarks may 

 be here made. There can not be a doubt that the registry 



Illustrations of / 



the vestiges of of impressions involves an actual structural change in the 

 impressions. g an glion, which is of a permanent character. These changes 

 may be rudely and imperfectly illustrated by experiments, such as I pub- 

 lished years ago, of which the following may be taken as examples : If, 

 on a cold, polished piece of metal, any object, as a wafer, is laid, and the 

 metal then be breathed upon, and, when the moisture has had time to 

 disappear, the wafer be thrown ofT, though now upon the polished surface 

 the most critical inspection can discover no trace of any form, if we 

 breathe upon it a spectral figure of the wafer comes into view, and this 

 may be done again and again. Nay, even more ; if the polished metal be 

 carefully put aside where nothing can deteriorate its surface, and be so 

 kept for many months (I have witnessed it even after a year), on breath- 

 ing again upon it, the shadowy form emerges ; or, if a sheet of paper on 

 which a key or other object is laid be carried for a few moments into the 

 sunshine, and then instantaneously viewed in the dark, the key being 

 simultaneously removed, a fading spectre of the key on the paper will be 

 seen ; and if the paper be put away where nothing can disturb it, and 

 so kept for many months, at the end thereof, if it be carried into a dark 

 place and laid on a piece of hot metal, the spectre of the key will come 

 forth. In the case of bodies more highly phosphorescent than paper, the 

 spectres of many different objects which may have been in succession 

 laid originally thereupon will, on warming, emerge in their proper order. 

 I introduce these illustrations for the purpose of showing how trivial 

 are the impressions which may be thus registered and preserved. In- 

 deed, I believe that a shadow never falls upon a wall without leaving 

 thereupon its permanent trace a trace which might be made visible by 

 resorting to proper processes. All kinds of photographic drawing are in 

 their degree examples of the kind. Of the moral consequences of such 

 facts it is not my object here to speak. The world would be none the 

 worse if every secret action might thus be made plain. But if on such 

 inorganic surfaces impressions may in this way be preserved, how much 

 more likely is it that the same thing occurs in the purposely-constituted 

 ganglion ! Not that there is any necessary coincidence between an ex- 

 ternal form and its ganglionic impression any more than there is be- 

 tween the letters of a message delivered in a telegraphic office and the sig- 

 interpretation na ^ s wn i cn tne telegraph gives to the distant station, yet these 

 ofsuchves- signals are easily retranslated into the original words no 

 more than there is between the letters of a printed page and 

 the acts or scenes they may chance to describe, but those letters call up 

 with clearness in the mind of the reader the events and scenes. Indeed, 

 the quickness with which the mind interprets such traces or impressions 



