838 THE SPINAL CORD. 



activity of another part had, from its psychological aspect, long been 

 expressed ; for instance, in the " duobus doloribus simul abortis non in 

 eodem loco vehementior obscurat alterum " of Hippocrates. 1 As a 

 working physiological thesis it only became accepted doctrine after 

 Setschenow 2 in 1863. He found that stimulation of the mid-brain and 

 bulb, especially of the corpora quadrigemina, prolongs the reflex time. 

 A frog, its cerebral hemispheres having been removed, withdraws its 

 foot from a bath of acidulated water, if the above-mentioned parts are 

 at the same time excited, much later than it does otherwise. The 

 postulation of an inhibitory centre in the mesencephalon (and myelen- 

 cephalon) was the first interpretation put upon Setschenow's observa- 

 tions. Then it was shown that similar inhibitions of spinal reactions 

 could be obtained from foci in various other parts of the brain, 3 and of 

 the cord itself. 4 The inhibitions are obtained either mediately from 

 sensorial surfaces, or by immediate excitation of the foci themselves. 

 Goltz 5 introduced the view that a reflex centre, engaged in a particular 

 reflex function, suffers impairment of activity for that particular reflex 

 when it receives incitation from any other afferent channel. Schiff and 

 Herzen teach that each spinal segment exerts an inhibitory influence 

 on all segments lying further backward. Certain it is, a nerve cell 

 thrown into activity may throw others not only into action but also out 

 of action. 



Where, as in the higher mammals, the cord possesses an immediate 

 path from a region of the cerebral cortex, it is considerably influenced 

 in its reflex functions by the activity of that cortex. Eeflexes purely 

 spinal are facilitated by the removal of this cortex or by the rupture 

 of its descending path. The scratching reflex, which is easy to evoke 

 from puppies and from the adult dog after high spinal transection, 

 can, after ablation of the cortex cerebri, be abnormally easily and 

 even uncontrollably elicited on the side of the body contralateral to the 

 cerebral lesion. 6 A monkey, in which a brachioplegia has been caused 

 by ablation of the cortical arm area, when one month subsequent to 

 the cerebral ablation the mesencephalon is transected, shows in the 

 decerebrate condition an extraordinary degree of reflex responsiveness 

 in the monoplegic limb to stimuli of the fellow fore-limb, and of the 

 hind-limbs, ears, and other reflexigenous zones. 



Various explanations have been offered for the facilitation of spinal reflexes 

 which ensues on removal of the cortex. It has been argued (1) that the 

 energy reflexly set free in the central nervous system is separable into that 

 which is liberated in the brain and that liberated in the reflex spinal machinery, 

 and that when the former liberation is no longer possible, the latter absorbs 

 vicariously the excess. 7 The view has nothing in its favour. It has been 

 further argued (2) that the Wallerian degeneration of the pyramidal tract acts 



"Aphorisms," Bk. ii. p. 46. 



2 " Physiol. Studien ueber d. Hemnmngsmechauismen f. d. Refl.," Berlin ; and with 

 Paschutin, " Neue Versuche," Berlin, 1865 ; also Bull. Acad. imp. d. sc. de St. 

 Petersboiirg, tome xx. p. 537 ; and "Ueber d. elekt. u. chem. Reizung d. sensiblen Nerven 

 u. Riickenmarks d. Frosches," Graz, 1868. 



3 L. N. Simonoff, Arch. f. Physiol. , Leipzig, 1866, S. 545; J. Ott, Journ. Physiol., 

 Cambridge and London, 1881, vol. iii. p. 163. 



4 A. Herzen, " Experiences sur les centres mode"rateurs de Faction re'flexe," Turin, 1864 ; 

 Lewisson, Arch. f. Physiol., Leipzig, 1869 ; Nothnagel, Virchows Archiv, 1873, Bd. xlix. ; 

 Tarchanoff, Journ. dlya normal, i patol. gistologii, St. Petersburg, 1872, vol. v. p. 285. 



5 " Beitrage z. Lehre v. d. Functionen d. Nervencent. d. Frosches," Berlin, 1869. 



6 Gergens, Arch. f. d. ges. Physiol., Bonn, Bd. xiv. S. 340. 



7 Brown-Sequard, "Sur la physiologic de la moelle epiniere," 1855. 



