246 Proceedings of 



more or less folded externally in different 

 animals, entirely covered with greyish 

 matter, and reflected upwards to cover 

 Ihem again, by forming what are called the 

 hemisplieies ; and which, after bending 

 down between them, nnites itself to that 

 of the opposite side by one or more com- 

 missures or fascioli of transverse fibres, 

 the most considerable of which, existing 

 only in the Mammiferje, is called corpus 

 eallosum. It is also well known that upon 

 the o'ura cerebri, behind t!ie optic tkalami, 

 are one or two pftir of lesser enlargements, 

 known, when there are two pair, as in the 

 Mammiferw, nnder the name of tuhercula 

 ijuudrigemina, from the fiist of which the 

 optic nerves appear to take their origin ; 

 that the olfactory nerve is the only one 

 ■which docs not sensibly arise from the 

 spinal marrow, or from its branches; and 

 that the cerebellum, an irregular mass ex- 

 ternally white, and internally cineritious, 

 like the hemispheres, but often mncii more 

 divided by exterior folds, is situated cross- 

 wise behind the tubercula quadrigcmina, 

 and upon the medulla oblongala, with which 

 it is connected by transverse fasciculi, 

 which are called crura cerebelli, and which 

 join it on either side of the pons Varolii. 

 In these masses, so different and so com- 

 plicated, it was necessary to seek the 

 j)oint from which irritation proceeded, and 

 that at which sensation terminated ; ii was 

 necessary to ascertain their respective co- 

 operation in the acts of the will ; and this 

 is what M. Flourcns has especially la- 

 boured to accomplish 



He has examined, first, how high we 

 must ascend to produce eiHcacious irrita- 

 tions on the muscular system; and he has 

 discovered a point at wliirh these irritations 

 were powerless; then proceeding to the 

 opposite side of the encephalus, he has 

 irritated it more and more profoundly, so 

 long as it did not act upon the muscles ; 

 and, when it bfgau to act, he found himself 

 again at the same place where its action 

 had stopt in ascending. This is also the 

 place at which the sensation of excitations 

 directed against the nervous system stops ; 

 above it, punctures and wounds may be in- 

 liicted without causing pain. Thus M. 

 Flourens punctured the hemi''plieret, with- 

 out producing either contraction in the 

 muscles, or appearance of pain in the ani- 

 mal ; he removed them in successive 

 laminae; he performed tiie same operation 

 on the cerebellum ; he took away, at the 

 same time, the hemispheres and the 

 cerebellum. The animal remained impas- 

 sive. The corpora striata and the optic 

 tlialami were attacked and removed, witli- 

 out producing any other effects. I'he iris 

 was rot even contracted in consequence, 

 nor was it subsequ<'ntly paralysed. But, 

 when he pimctnrcd the tuhercula <iuadri- 

 ((eminn, trembling and convulsions imme- 

 diately took place, and increay^i! in pro- 



Public Societies. [April If 



portion as he penetrateil more deeply into 

 xXxemeduUa oblongata. The pricking of these 

 tubercula, or of the optic nerve, produced 

 acute and prolonged contractions of tlic 

 iris. 



M. Flourens concludes, (to use his pecu- 

 liar language), that the medulla oblongata 

 and the tuhercula are irritable; which in 

 ours signifies that tliey are, like the spinal 

 marrow and the nerves, cniluctors of irrita- 

 tion ; but that neither the cerebrum nor the 

 cerebellum has that property. The author 

 concludes, also, that the«e tubercles form 

 the continuation and the superior termina- 

 tion of the spinal marrow and the medulla 

 oblongata; and this conclusion is in perfect 

 conformity with their relations and anato- 

 mical connexions. 



Wounds of tlie cerebrum and cerebellum 

 produce neither pain nor convulsions ; and, 

 m ordinary language, we should thence 

 pronounce that the cerebrum and cerebellum 

 are insensible. But M. Flourens says, on 

 the contrary, that these are the sensible 

 parts of the nervous system ; which only 

 means, that they are the j>arts at which the 

 impression received by the sensible organs 

 must arrive, before the animal can experi- 

 ence a sensation. 



M. Flourens appears to us to have com- 

 pletely proved this proposition, as far as 

 regards the senses of sight and hearing. 

 When the cerebral lobe of an animal is 

 removed on the one side, it no longer sees 

 with the eye of the opposite .side, although 

 the iris of that eye preserves its mobility : 

 when both lobes arc removed, it becomes 

 blind and deaf. 



The animal thus mutilated assumes a 

 torpid air; he neither himself originates 

 any act of volition, nor perforins any spon- 

 taneous movement ; but when he is stricken 

 or wounded, he exhibits all the appearance 

 of mi animal exercising its usual functions. 

 In whatever position he is placed, he re- 

 sumes his equilibrium : it' he be laid on his 

 back, he turns himself round again : if 

 pushed, he moves onward : if the animal be 

 a frog, it leaps on being touched ; if a bird, 

 it flies on being thrown up into the air ; it 

 struggles when put to pain or inconveni- 

 ence ; and, if water is dropped into its 

 beak, it swallows it. 



The animal removes himself from the 

 cause of irritation, without any further in- 

 tention; he has no memory, and will re- 

 peatedly strike or stumble against the same 

 obstacle: but this proves at most, to use 

 the expression of M. Flourens, that the 

 animal is in a state of sleep. Indeed he 

 moves and acts precisely like a sleeping 

 man ; but we are far from believing that a 

 man, while asleep, who moves himself into 

 the most convenient positions and attitudes, 

 is absolutely without sensations ; nor does it 

 by any means follow, because his percep- 

 tion of them M'as indistinct, and because 

 he has retained no recollection of them, 



that 



