CHAP. vi. J SOME OTHER SENSATIONS. 299 



he knows them well. When a direct appeal is made to his 

 consciousness he appears to possess little or no muscular sense ; he 

 is unaware, so long as his eyes are shut, of the position of the 

 limbs affected by the disease, and if the arms are affected is unable 

 properly to judge weights. 



These cases of " tabes " are very varied in their symptoms, 

 which indeed alter as the disease advances. Concerning them 

 and similar phenomena presented by other allied nervous diseases 

 there has been much discussion; but the evidence afforded by 

 them, supported as it is to a certain extent by experimental 

 results, is strongly in favour of the view that the afferent impulses 

 which determine coordination and which go to make up what we 

 are now calling the muscular sense are other than those started in 

 the skin. 



We may therefore dismiss cutaneous sensations as not being- 

 essential factors of the sense. 



894. There remain on the one hand the muscles, on the 

 other the joints with their belonging ligaments and tendons ; the 

 afferent impulses under discussion must come from one or other 

 or both of these. 



Against the view that the afferent impulses of the muscular 

 sense come from the muscles themselves has been urged the fact 

 that, tested experimentally, muscular fibres in a normal condition 

 possess 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 circumstances, as when a 

 muscle is 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 condition possess a similarly feeble 

 general sensibility, but it supposes that the muscular sense is 

 merely a development of general sensibility not a special sense, 

 like that of touch. We have no positive reasons for this suppo- 

 sition, and arguments based on the analogy of the skin oppose it. 

 We have seen reason to regard the cutaneous sensations of 

 pressure and temperature as wholly distinct from those of general 

 sensibility, that is to say of pain and we may conclude that the 

 muscular sense is similarly a special sense, similarly distinct from 

 affections of common sensibility in either muscular fibres or their 

 connective tissue appendages. 



On the other hand afferent impulses may proceed from 

 muscles, for when a nerve twig going to a muscle is stimulated 

 centripetally, after division, reflex movements result; if the 

 stimulus is weak the movement is confined to the muscle itself 

 (we are supposing that other nerve twigs going to the muscle are 



