EFFECTS OF LOSS OF MUSCULAR SENSE. 1019 



how consciousness comes not to be involved in them, there are several 

 probabilities to oiler. Unhesitating fatality and speed are characters 

 which consciousness might only impede, though, for certain nervous 

 reactions, these very characters would be beneficial to the race. 

 Another suggestion would be, that division of attention appears, from 

 the constitution of mind, to undermine all exquisiteness of performance. 

 Excitation of the afferent nerve fibres in the nerve trunk of a 

 skeletal muscle produces, apart from and more readily than those 

 general reflexes, vasomotor, etc., above-mentioned, special reflexes upon 

 the local musculature. The above-mentioned general reflexes are only 

 positively indicative of that degree of common sensation in which 

 sense-feeling is dominant and painful. The local reflex effects on the 

 musculature obtained from afferent muscle nerves by weaker stimuli, 

 are more special in character, and more significant for the study of 

 muscular sense, especially in its relation to co-ordination. If, when 

 the cranio-spinal axis has been transected just in front of the pons, 

 and " decerebrate rigidity " has set in, the purely muscular nerve trunk 

 of one of the flexor muscles of the knee is cut, and its central end 

 excited by ligation or faradisation, the existing strong tonic contraction 

 of the extensor muscles of the knee is at once relaxed, 1 and the fellow- 

 muscles of the flexor group, previously inactive and flaccid, are at the 

 same time thrown into contraction. The same result may be brought 

 about also by stretching or compressing the muscles themselves, so long 

 as their afferent nerves are intact. The excitation of the sensory nerve 

 fibres from the flexor muscles, besides provoking contraction of the fellow- 

 flexors, inhibits the contraction (and even the tonus) of the antagonist 

 group. In this experiment the sensory impulses arising in one muscle 

 influence the activity of the motor nerve cells governing its fellow- 

 muscles, and of those governing its antagonists, augmenting the former, 

 diminishing and even annulling the latter. Acting thus, the centripetal 

 impulses from the muscle produce an important item of spatial co-ordina- 

 tion, which I have termed " reciprocal inner vation." 2 This effect of the 

 centripetal impulses from the muscle is not accompanied, it would seem, 

 by psychosis. Kinsesthesis, in the psychological sense, seems precluded 

 where the whole cerebrum had been removed. Muscular " sensations " can 

 hardly have been present; indeed, similar observations can be made 

 even when the whole brain has been cut off by transection at the top of 

 the spinal cord itself. The co-ordination of the movements of the 

 spinal frog is suggestive of regulation by afferent nerves, probably 

 muscular. I found the initial posture of the limb in the spinal animal 

 (e.g. frog) distinctly affect the character of the reflex movement elicit- 

 able from the limb even in the absence of cutaneous organs. The co- 

 ordination was therefore evoked by impulses from the peripheral organs 

 and nerves of muscular sense, in the absence of all the nervous machinery 

 from which one is accustomed to consider consciousness indissoluble. 



How little ordinary consciousness is involved by the lower performances of 

 muscular sense, is instanced by the untying of the hands during sleep, even 

 although the knots used for confining them be of a quite complex kind. The 

 two distinct cortical regions related to the movements of the eyeballs accords 

 with the evidence mentioned above in favour of the regulation of those move- 

 ments by intrinsic muscular sensations (frontal cortex), as well as by visual 

 (retinal) sensations (occipital cortex). 



1 Sherrington, Proc. Roy. Soc. London, 1893, vol. lii. 2 Ibid., 1896, vol. lix. 



