62 NERVOUS SYSTEM. 



are by no means the seat of the soul, as held by certain au- 

 thorities; these are only bridges of white substance that 

 harmonize the functions of the two hemispheres which they 

 connect ; but here, moreover, we must not attach a meaning 

 to words nor pretend to a decision not supported by the facts ; 

 as, for instance, is done by Treviranus, who asserts that the 

 corpus callosum furnishes the brain with the faculty of com- 

 parisons, as if comparison were made between the thoughts 

 which come from the left and right, and not between impres- 

 sions, or successive thoughts (Duges). 



The cerebral hemispheres, and especially their gray cortical 

 substance, are the most essential portion of the brain. Here 

 are accomplished the elaborations of the sensations in the 

 form of thoughts. The experiments of Flourens, from which 

 Longet especially has drawn legitimate conclusions, prove 

 that animals from which the hemispheres hare been removed, 

 as^we have before remarked in connection with the protuber- 

 ance and tubercula quadrigemina, continue to feel, hear, see, 

 and receive the impressions of taste ; but that these impressions 

 do not remain nor awake any' response, nor seem to produce 

 any associations of ideas ; they do not look nor hear, nor 

 smell, nor taste; in short, the cerebral lobes " are the recep- 

 tacle where all sensations take a distinct form, and produce 

 a continued remembrance." There may be a perfect sensa- 

 tion without the cerebral lobes ; but this sensation bears a 

 resemblance to that effect which is noticed in a person wrapt 

 in profound meditation, and receiving an external irritation 

 (as, for instance, when a fly lights upon the hand), but whose 

 meditation is not in any way interrupted, and who does not 

 appear to notice the irritation (Vulpian, Taine). 



On the other hand, the cerebral lobes preside over spon- 

 taneous movements. An attentive analysis of the movements 

 of a frog or of a fish deprived of the cerebral lobes proves 

 that these creatures swim only under the influence of reflex 

 actions perfectly co-ordinated, which the impression of the 

 water in contact with their integument may provoke ; they 

 progress as if impelled by a pre-established mechanism, as ii 

 subjected to a reaction which makes their progress an imperi- 

 ous necessity, until a new impression, as for instance coming 

 in contact with the borders of the vessel or basin, causes the 

 frog to assume a state of immobility and normal posture, a 

 necessity no less imperious than the first. There are not 

 Been in the behavior of the animal any of those capricious 

 changes, or spontaneous movements from repose to activity 



