36 MENTAL EVOLUTION IN ANIMALS. 



between the repetitions of its activity, as every one must 

 know who is in the habit of playing on a musical instrument, 

 or performing any other actions entailing the acquirement of 

 dexterity. It may also be observed that when such is the 

 case the particular activity forgotten by the ganglion may be 

 more easily re- acquired than originally it was acquired, which 

 is just what we find to be the case with mental attainments. 



As particular illustrations of these facts I may state two 

 or three cases, which will also serve to show of how little 

 importance (on the objective side) is the occurrence of con- 

 sciousness to the memory of a ganglion. 



Eobert Houdin early in life practised the art of juggling 

 with balls in the air, and after a month's practice was able to 

 keep four balls in the air at once. His neuro-muscular 

 machinery was now so well trained, or remembered so well 

 how to perform the series of actions required, that he could 

 afford to withdraw his attention from the performance to the 

 extent of reading a book without hesitation while keeping 

 up the four balls. Thirty years afterwards, on trying the 

 same experiment, having scarcely once handled the balls 

 between times, he found that he could still read with ease 

 while keeping up three balls ; the ganglia concerned had 

 partly forgotten their work, but on the whole remembered it 

 w^onclerfully well. Again, Lewxs gives the case of a waiter 

 asleep at a coffee-house, with much noise of talking around 

 him, who was instantly aroused by a low cry of " Waiter ;" 

 and Dr. Abercrombie gives the case of a man who had long 

 been in the habit of taking down a repeater watch from the 

 head of his bed to make it strike the last hour, and who 

 was observed to do this when otherwise apparently uncon- 

 scious from a fit of apoplexy. But perhaps the most remark- 

 able of all the cases that can be adduced are the most familiar 

 ones of walking and speaking. When we remember the 

 immense amount of neuro-muscular co-ordination that is 

 required for either of these actions, and the laborious steps 

 by which each of them is first acquired in early childhood, it 

 is indeed astonishing that in after life they come to be per- 

 formed without thought of their performance ; the ganglia 

 concerned have fully learned their work. 



So much for memory. But memory would be a useless 

 faculty of mind if it did not lay the basis for another, and 

 really the most important principle of subjectivity; I mean 



