MEMORY AND ASSOCIATION OF IDEAS. 113 



curious fact to hold in the case of muscular tissues of various 

 animals, from the Medusa? upwards.* 



Again, I concur with M. Eibot in his opinion that the iy 

 physical basis of memory consists partly in a more or less "^ 

 permanent molecular change or " impress " produced upon 

 the nervous element affected by the stimulus which is re- 

 membered, and partly upon " the establishment of stable ■^■ 

 connections between different groups of nervous elements." 

 I do not think that the view can be too strongly reprobated 

 which crudely supposes that the first of these physical con- 

 ditions is alone sufficient to explain all the facts of memory, 

 and therefore that a given remembrance is, as it were, stored 

 up in a particular cell, as a particular *' impression " upon 

 the substance of that cell. On the contrary, as M. Eibot 

 shows, " Each of these supposed unities (memories) is com- 

 posed of numberless and heterogeneous elements ; it is an 

 association, a group, a fusion, a complexus, a multiplicity; 



. . . . Memory supposes not only a modification of , 

 nervous elements, hut the formation among them of determi- 

 nate associatio7is for each particular act. We must not, how- 

 ever, forget that this is pure hypothesis — the best available 

 one, no doubt, but still not to be taken as implying that we 

 really know anything definitely concerning the physical sub- 

 stratum of memory." 



Erofound, however, as our ignorance unquestionably is 

 concerning the physical substratum of memory, I think w^e 

 are at least justified in regarding this substratum as the same 

 both in ganglionic or organic, and in conscious or psycholo- 

 gical memory — seeing that the analogies between the two are 

 so numerous and precise. Consciousness is but an adjunct 

 which arises when the physical processes — owing to infre- 

 quency of repetition, complexity of operation, or other causes — 

 involve what I have before called gans^lionic friction. And 

 this view is confirmed by the large and general fact noted in 



* See " Coneludiug Obserrations on tlie Locomotor System of Medusa?," 

 Fhil. Trans., Pt. I, 1880; and on "Modification of "^Excitability," &e., 

 Froc. Foy. Soc, Nos. 171 and 211. Also, Journal of Anatomy and Physio- 

 logy, Tol. X. Another equally good instance of what may be termed proto- 

 plasmic memory is to be found in the facts of the so-called " summation of 

 stimuli," which occur more or less in all excitable tissues, i.e., -nherever 

 living protoplasm is concerned. These facts are that if a succession of 

 stimuli are applied to the excitable tissue, the latter becomes progressively 

 more and more quick, as well as more and more energetic, in its response ; 

 each stimulus leaves behind it an organic memorj of its occurrence. 



H 



