220 ANIMAL AUTOMATISM. 



lecules, which gives rise to the idea of the thing remem- 

 bered, is no less certain. Every boy who learns his 

 lesson by repeating it exemplifies the fact. Descartes, 

 as we have seen, supposes that the pores of a given part 

 of the brain are stretched by the animal spirits, on the 

 occurrence of a sensation, and that the part of the brain 

 thus stretched, being imperfectly elastic, does not return 

 to exactly its previous condition, but remains more dis- 

 tensible than it was before. Hartley supposes that the 

 vibrations, excited by a sensory, or other, impression, 

 do not die away, but are represented by smaller vibra- 

 tions or " vibratiuncules," the permanency and intensity 

 of which are in relation with the frequency of repetition 

 of the primary vibrations. Ilaller has substantially the 

 same idea, but contents himself with the general term 

 " mutationes," to express the cerebral change which is 

 the cause of a state of consciousness. These "muta- 

 tiones" persist for a long time after the cause which 

 gives rise to them has ceased to operate, and are arranged 

 in the brain according to the order of coexistence and 

 succession of their causes. And he gives these persistent 

 " mutationes " the picturesque name of vestigia rerum, 

 " quse non in mente sed in ipso corpore et in medulla 

 quidem cerebri ineffabili modo incredibiliter minutis 

 notis et copia infinita, inscriptse sunt." * I do not know 

 that any modern theory of the physical conditions of 

 memory differs essentially from these, which are all chil- 

 dren mutatis mutandis of the Cartesian doctrine. 

 * Haller, " Primes Lines," ed. iii. " Sensus Interni," dlviii. 



