

OF THE CEREBRO-SPINAL SYSTEM. 69 



lability^ he applies to the property of exciting sensation and motion, without evincing 

 or experiencing them. This application of the word is by no means judicious; it must 

 however, be allowed, that it i3 not easy to find a term which can convey the meaning 

 wished to be attached to it. 



The questions proposed by Mr Flourens, and which he lias endeavoured to ascertain 

 by experiment are : 1st, from what points of the nervous system artificial irritation may 

 jet oft' to arrive at a muscle ; 2cl, to what points of this system an impression must be 

 propagated to produce sensation ; 3d, from what points voluntary irritation descends, 

 and what parts of this system most be influenced to produce it regularly. 



M. Flourens commenced with the nerves, and fully confirmed the views usually enter- 

 tained respecting their functions. He has shown, in a satisfactory manner, ' that, hi 

 order to effect contraction, a free and continued communication is requisite between the 

 nerve and i. I that to produce sensation, a similar communication with the 



brain is equally necessary. '5-nce 1;?. concludes, that neither contraction nor sensation 

 belong to the nerve ; that these two effect ,'U they may take place in- 



dependently of each other ; and that these propositions hold good, at whatever pia't, 

 and in whatever branch of a nerve the communication is interrupted. 



** Employing the sante method with regard to the spinal marrow, he arrived at similar 

 conclusions. When it is irritated in any given point, contractions are excited in all the 

 muscles which derive their nerves from below this point, if the communication remains 

 free but not if the communication be interrupted. Exactly the reverse obtains with 

 regard to sensation ; and, as in the nerves, the government of the will requires th 

 same freedom of communication as sensation, the muscles beneath the intercepted part 

 no longer obey the animal, and he has no feeling in them : in fine, if the spinal mar- 

 row be intercepted at two points, the muscles which receive their nerves from this in- 

 terval experience contractions alone ; but the animal does not command them, nor receive 

 from them any sensation." M. F. farther inferred, from his experiment respecting the 

 functions of the spinal marrow, that sensation and contraction belong no more to it 

 than to the nerves. 



He next directed his researches to the brain, in order to ascertain the point whence 

 irritation departed, and point where the sensation arrives, and to determine their 

 respective co-operation in acts of volition. Advancing from the medulla oblongata 

 towards the hemispheres, Mr. Flourens first examined how far it was possible to go, and 

 still produce sufficient irritation on the muscular system, when he arrived at a point 

 where these irritations disappeared : " then taking the brain at the opposite part, he 

 irritated it at points deeper and deeper, as long as he did not act upon the muscles ; and 

 when he did begin to act upon them, he found himself at the same point where the ac- 

 tion had ceased in ascending. This part is -also that where the sensation of irritation ap- 

 plied to the nervous system likewise ceases : above this, punctures and wounds do not 

 excite pain. Thus M. Flourens pricked the hemispheres without producing contraction 

 of the muscles, nor the appearance of pain in the animal ; he removed them in successive 

 slices ; he did the same with regard to the cerebellum ; he removed at once the hemis- 

 pheres and cerebellum. The animal remained passive. The corpora striata and the 

 optic thalanil were attacked, and removed without any other effect : the iris was not con- 

 tracted, nor even paralysed. But when he pricked the t-ubercula quadrigemina, trem- 

 bling and convulsions began, and these increased in proportion as he penetrated into 

 the medulla oblongata. Pricking the tubercles, as well as the optic nerve, produced 

 quick and continued contraction of the iris. These experiments agree with those of 

 Lorry, published in third volumeof the ' Mgmoires des Savans etnmgers.' < Neither the 

 irritation of the brain, nor of the corpus callosum itself produce convulsions : it may even 

 be removed with impunity. The only part among those contained in the brain which 

 has appeared uniformly and universally capable of exciting convulsions, is the medulla 

 oblongata: it is this part which produces them to the exclusion of every other.' They 

 contradict the experiments of Haller and Zinn with regard to the cerebellum ; but, 

 from what M. Flourens has sc>en and pointed out, it appears that these physiologists had 

 touched the medulla without being aware of it. He concludes that the medulla oblon- 

 gata and the tubercles are (in his language) irritable ; which means that they are con- 

 ductors of irritation, like the spinal marrow and nerves, but that neither the cerebrum nor 

 cerebellum possess this property. The author hence concludes, likewise, that these 

 tubercles form the continuation and superior termination of the spinal cord and medulla 

 oblongata; and this opinion is in conformity with their situation and anatomical con- 

 nexions. 



Wounds of the brain and cerebellum do not excite pain any more than convulsions. 

 Hence M. Flourens infers that to them, the impression received by sensible organs 

 must be conveyed, in order that the animal may experience a sensation. He appears 



