1064 ON CUTANEOUS AND [BOOK in. 



rise to afferent impulses. On the other hand afferent impulses 

 may proceed from muscles. When, for instance, a nerve twig 

 going to a muscle is stimulated, centripetally, after division, 

 reflex movements result ; if the stimulus is weak the move- 

 ment is confined to the muscle itself (we are supposing that 

 other nerve twigs going to the muscle are left intact) ; if 

 the stimulus is strong, the movement spreads to neighbouring 

 muscles. Again, the phenomena often spoken of as 'muscle 

 reflexes' such as the ' kn^e-jerk ' and the like ( 515) are all 

 so many proofs of afferent impulses passing up from the mus- 

 cles. In speaking of the knee-jerk, we called attention to the 

 influence exerted upon the movement of the muscle employed, 

 by afferent impulses proceeding from the antagonistic muscles ; 

 and instances might be multiplied of the action and ' tone ' 

 of one muscle being modified by afferent impulses pass- 

 ing up from its antagonist to the nervous centre. And 

 undoubtedly muscles are well supplied with afferent fibres. 

 When the anterior roots, fibres from which supply a given 

 muscle, are cut, a very large number of the nerve fibres present 

 in the muscle remain undegenerated ; these, which end partly in 

 the tendon by a plexiform arrangement of fibrils terminating in 

 minute end-bulbs known as the organ of Golgi, but partly and 

 indeed largely in a somewhat similar manner, in connection with 

 the muscular fibres themselves, seem to be undoubtedly afferent 

 fibres. Hence we have anatomical support for the view that 

 the afferent impulses of the muscular sense may come from the 

 muscles and their tendons no less than from the joints. In at- 

 tempting further to distinguish between the actual muscular 

 fibres themselves and the tendons as the source of these im- 

 pulses while admitting that the tendon form part of the 

 source, we may conclude that the above-mentioned termina- 

 tions of afferent fibres among the muscular fibres themselves 

 indicate that these also form another part; and this view is 

 supported by the connection, also mentioned above, of fatigue 

 with the muscular sense. 



Against the view that the afferent impulses of the muscular 

 sense come from the muscular fibres themselves has been urged 

 the fact that these, tested experimentally, possess in a normal 

 condition a very feeble general sensibility; when a muscle is 

 cut or pinched comparatively little or, according to some 

 observers, no pain is felt; it is only under abnormal circum- 

 stances, as when a muscle \s inflamed, that direct stimulation 

 of this kind causes pain ; and the pain which we feel in 

 cramp is similarly the product of an abnormal condition, for 

 even an extremely violent muscular effort does not cause 

 us actual pain. This argument however -is not valid, for 

 not only may it equally well be applied to the other set of 

 tissues, tendons, ligaments and the like, which in a normal con- 



