50 INTRODUCTION. 



selves. Dreams, visions, and many casual sensa- 

 tions exemplify the truth of this observation. 



By central masses we mean, a certain portion 

 only of the nervous system, which is always more 

 circumscribed in proportion to the greater perfec- 

 tion of the animal. In man it is exclusively a re- 

 stricted portion of the brain, but the entire brain, 

 and the medullary composition of each part sepa- 

 rately considered form the sensorium of reptiles, 

 consequently the absence of the brain in them does 

 not destroy the faculty of sensation. The sensitive 

 power is still more diffusely extended among the 

 inferior classes of animals. 



* The perception acquirer 3 by the mind produces 



* This passage in the original is equally obscure with the sub- 

 ject, and as we do not profess to have a clear satisfactory notion 

 of either, a translation as literal as possible has been adopted. For 

 the satisfaction of the reader, however, we shall subjoin the passage 

 in French, and crave his indulgence for hazarding a few remarks 

 of our own. 



" La perception acquise par le moi produit l'image de la sensa- 

 tion eprouvtie. Nous reportons hors de nous la cause de la sen- 

 sation, et nous nous donnons ainsi 1'idee de l'objet qui l'a pro- 

 duce. Par une loi necessaire de notre intelligence, toutes les 

 idees d'objets materiels sont dans le temps et dansl'espace." 



There is nothing in all the economy of nature more mysterious 

 than the manner in which the mind acquires its notions of external 

 objects, and its belief in their existence. Volumes have been 

 written, and the most ingenious philosophers have laboured in 

 vain to explain the modus operandi of perception, but the wisest 

 have agreed to consider it as a mystery, placed beyond the limits 

 of human comprehension. In the brief passage above quoted 

 our author makes an abortive attempt to elucidate the mys- 

 tery, and presents us with a sort of theory of perception, which 

 appears, to us at least, quite destitute of proof. His meaning, if 



