of M . Flourens on the Nervous System. 1 23 



with the rest of the system, it is still further supported by a 

 fact in compai'ative anatomy, that the intelligence of animals 

 is constantly proportioned to the volume of these lobes. 



Having observed the effects of the ablation of what may be 

 strictly called the brain, M. Flourens proceeds to examine 

 those of the extirpation of the tubercula quadrigemina. The 

 excision of one of these tubercles, after a convulsive motion 

 of short duration, produces a durable bhndness of the eye on 

 the opposite side, and an involuntary giddiness ; that of both 

 tubercles, renders the blindness more complete and the giddi- 

 ness more violent and prolonged. The animal, however, re- 

 mains in possession of its other faculties, and the iris retains 

 its contractility. The deep extirpation of the tubercle, or the 

 section of the optic nerve, produces only paralysis of the iris ; 

 whence M. Flourens concludes that the ablation of the tuber- 

 cle has no other effect than would follow the section of the 

 nerve ; that the tubercle, therefore, is only a conductor of vi- 

 sion ; and that the cerebral lobe alone is the term of the sensa- 

 tion of sight, and the place in which it is completed, by being 

 converted into a perception. 



He observes, that when the extirpation of the tubercles is 

 too deeply performed, the medulla oblongata is affected, and 

 gives rise to violent and continued convulsions. 



The most curious and novel part of the experiments of M. 

 Flourens seems to us to be that which concerns the functions 

 of the cerebellum. 



During the ablation of the first laminae, he observed no- 

 thing more than a slight weakness, and a want of connexion 

 in the motions of the animal. When the middle laminae were 

 removed, a nearly general agitation was manifested. The ani- 

 mal, though still seeing and hearing, performed motions only in 

 an uncertain and hasty manner. Its faculty of flying, walking, 

 and retaining the erect posture, was gradually lost. When 

 the cerebellum was removed altogether, the faculty of perform- 

 ing regulated motions entirely ceased. Placed upon its back, 

 the animal no longer turned itself: it nevertheless perceived 

 the blow with which it was menaced ; it heard cries, and 

 endeavoured to avoid danger by a thousand fruitless efforts : 

 in a word, it retained its faculties of sensation and volition, 

 but had lost the power of producing voluntary muscular 

 contractions. It was scarcely able to keep its erect position, 

 by supporting itself with its wings and tail. 



The extirpation of the brain had produced a state of sleep ; 

 the excision of the cerebellum produced one of intoxication. 



" It is astonishing," says M. Flourens, " to observe the pi- 

 geon lobing by degrees, as its cerebellum is removed, the fa- 



Q 'I culty 



