RELATION OF AFFERENT TO EFFERENT ROOTS. 80 1 



stimulation of the part of the cortex which produces movement through those 

 cells, they seem slightly more excitable. 1 It was noted above that excitation of 

 the dorsal columns of the cord close to the bulb produces movements in the 

 homonymous limbs. The section of the afferent roots of the limb renders 

 this reaction much more difficult for that limb, 2 though it is still as easy as 

 before to evoke movements of the limb from the pyramidal tract. The signifi- 

 cance of this result may be that the severance of the axon from the cell body 

 and its cellulipetal processes, detaches the collaterals from their synapses with 

 the motor cells. That the change induced is not located in the motor root cell 

 itself, seems evident from the openness of the cortico-spinal synapse. 



Panizza, 3 who was the first after Mageudie to fully confirm the 

 Bell-Magendie law of the roots in warm-blooded animals, drew atten- 

 tion to the fact that though his experiments showed the dorsal 

 (posterior) roots to be wholly afferent, yet the section of a number of 

 the afferent roots brought marked impairment of the local motility. 

 The movements of the apaesthetic limb are clumsy. The hind-limb in 

 walking is lifted too high and set too far. Stilling 4 reaffirmed these 

 observations after experimenting on the afferent roots of the frog. He 

 wrote 



" The posterior roots have the following important functions : (1) 

 They maintain continuously the tonus of the muscles, or that action 

 whereby even in time of rest a ceaseless readiness for movement, a 

 ceaseless tension of the muscle fibres, is maintained. (2) The posterior 

 roots transmit continuously the sensation of the condition of the muscles 

 themselves. Each unsuitable, uncomfortable pose of the muscle is 

 thereby brought to consciousness, and, as a result, corrected by the will 

 or by reflex action." 5 



Claude Bernard 6 and Schiff 7 simultaneously later drew attention to the 

 disturbance of movement produced by the section of the roots. Bernard 

 pointed out that when the frog is held up by the body, the animal uses the 

 apaesthetic hind-limb far less than the sound one to release itself, and that 

 the creature springs with difficulty. He cut the afferent roots to one hind- 

 limb in young puppies, and noted that the animal could no longer support its 

 weight on that limb. 



H. E. Hering 8 has given a clear objectively written description of the 

 postures and movements of the apaesthetic limb in the frog. When the 

 animal is first approached the day after operation the apaesthetic limb is moved 

 up closely to the body, the normal limb moving much less. In the execution 

 of a small spring there is no obvious difference between the limbs ; in execu- 

 tion of a longer spring the animal alights so as to have its head facing some- 

 what towards the side of the apaesthetic hind-limb. If both hind-limbs are 

 apaesthetic, the spring is higher, but carries less far than normal ; the turn with 

 the one apaesthetic limb seems due to enfeebled extensor stroke. As the hind- 

 limbs are drawn up into the sitting posture again, after the spring, the apaes- 

 thetic one is seen to be the later, and to be tilted up in so doing. This latter 

 act constitutes Hering's "tilt-phenomenon," and he has shown by various 



1 Sherrington, Phil. Trans., London, 1892, vol. Ixxxviii. B ; Mott and Sherrington, 

 Proc. Roy. Soc. London, 1895, vol. Ivii. p. 481. 



2 Sherrington, ibid., 1897, vol. Ixi. p. 245. 



3 "Ricerche sperimentali sopra i nervi : Lettera del Professore Bartolomeo Panizza a 

 Professore Maurizio Bufalini," Pa via, 1834. This appeared in German, annotated by G. 

 Schneemann, with a preface by Eisenmann, at Erlangen, 1836. 



4 Arch. f. physioL ffeilk., Stuttgart, 1842, S. 97. 



5 Stilling, loc. cit. 6 "Systeme nerveux," loc. cit., 1858. 



7 " Lehrbucli d. Muskel- u. N erven physiologic," Lahr, 1858. 



8 Arch.f. exper. Path. u. Pharmakol., Leipzig, 1896, Bd. xxxviii. S. 266. 



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