RELATION OF AFFERENT TO EFFERENT ROOTS. 80 



o 



Hering 1 made the following observations on such ataxic animals. 

 When all the afferent brachial roots, except the last cervical, which I 

 have shown to supply the skin of the whole hand, are severed, the 

 monkey, in taking a piece of fruit offered him, exhibits zig-zag swaying 

 of the out-thrust arm. If a maize-corn be placed on the ledge of 

 the cage between the bars, the arm swaying, the more obviously the 

 further it is extended, often fails to make its grasp between the 

 right bars, and misses the object altogether. In picking small objects 

 such as rice-corns out of the observer's hand, the normal monkey 

 exhibits perfection of precision. He uses generally but finger and 

 thumb, and rarely touches the hand on which the corn is lying. The 

 monkey with its one afferent brachial root grasps clumsily with the 

 whole hand, and often meets the observer's hand and not its content. 



It has been pointed out that the movements of the proximal joints 

 of the limb suffer less impairment of movement than those of the distal. 

 It must be remembered that the number of nerve roots supplying the 

 musculature of the proximal joints is greater than the number of roots 

 supplying the distal. 2 The posture of the apresthetic hind-limb is an 

 almost continuously maintained strong flexion at hip and knee ; that of 

 the fore-limb, which swings helplessly, flexion at elbow and wrist, with 

 adduction at shoulder. Warrington has shown that severance of the 

 afferent roots causes degeneration in certain of the motor root cells 

 of the corresponding spinal region. 



Charles Bell 3 found that in the ass, after section of the supra- 

 maxillary divisions of both trigemini, the upper lip was no longer lifted 

 in feeding, and the same phenomenon has been observed in the rabbit 

 and cat. 4 Bell questioned in consequence whether the nerve might not 

 be motor. Experiments in Exner's laboratory 5 led to the conclusion 

 that in the horse a "paralysis" of the laryngeal muscles of one side 

 follows section of the corresponding sensory nerve of the larynx. This 

 observation has, it is true, been disputed, but a most striking example of 

 this kind is furnished by the ape. 6 After section of all the afferent roots 

 of the limb, the movement of grasp by hand or foot respectively is 

 permanently lost. If even only one of the sensory roots of the three 

 belonging to the hand and foot respectively is left to the limb, the loss 

 of the grasp does not ensue, although there is marked ataxy. Under 

 the most inducive and favourable circumstances, the wholly apa?sthetic 

 limb is never used for grasping. Yet, if the appropriate region of 

 the cortex is excited, the grasp is elicited with apparently perfectly 

 normal facility, and in the absinthe convulsions the closure of the hand 

 and foot is as equally exhibited as by the fellow normal limb. 6 



Electrical change in the opposite afferent root has been in some 

 cases found to accompany electrical excitation of the sciatic nerve of 

 one side. 7 In experiments on the frog, the electrical effect produced 



1 Neurol. Centralbl., Leipzig, loc. cit. Dr. J. L. Muskens tells me that after a time the 

 ataxy subsides. 



2 Sherrington, Joum. Physiol., Cambridge and London, 1892, vol. xiii. p. 1. 



a " Nervous System," 1820. Denied by Mayo, " Anat. and Physiol. Comment.," 

 London, 1822. 



4 Schoeps, Arch. f. Anat. u. Physiol., Leipzig, 1827, S. 409. 



5 Exner, Centralbl. f. Ph i/siol., Leipzig u. Wien, 1889, Bd. iii. S. 115 ; Pineles, ibid., 

 1890, Bd. iv. S. 741 ; Moller,'"Das Kehlkopi'pfeifen d. Pferdes," Stuttgart, 188S ; Pineles, 

 Arch./, d. ges. Physiol., Bonn, 1891, Bd. xlviii. S. 17. 



fi Mott and Sherrington, loc. cit.; Hering and Sherrington, loc. cit. 

 7 Gotoh and Horsley, Phil. Trans., London, 1891. 



