CHAP, vi.] SOME OTHEK SENSATIONS. 1063 



So long as his eyes are open he may be able to stand and walk, 

 but if his eyes are shut he often falls, and when he moves, 

 moves with a staggering uncertain gait ; he fears, in the dark, 

 to go up or down stairs even though 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 symp- 

 toms, 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. 



662. There remain on the one hand the muscles, with 

 which we may in the first instance include the belonging ten- 

 dons, and on the other hand the joints with their belonging liga- 

 ments ; the afferent impulses under discussion must come from 

 one or other or both of these. We cannot by an appeal to our 

 own consciousness localize the muscular sense so as to lodge 

 it exclusively either in the one or the other of these parts and 

 must trust to indirect indications. On the one hand there seems 

 to be a close connection between the muscular sense and the 

 4 sense of fatigue ; ' and the latter appears to be determined 

 by the condition of the muscles. Again, in many of our move- 

 ments we employ a part only of a muscle, and it is difficult 

 to suppose that the afferent impulses which guide us in using 

 that part only, depend alone on the effect which the partial 

 use of the muscle produces on the joints or other parts. On 

 the other hand, when we have a muscular sense of the move- 

 ments of the fingers, we can hardly suppose that the sense is 

 afforded by impulses coming exclusively from the muscles 

 moving the fingers, distant as these often are from the joints 

 which they move. And, again, the movements of which-we are 

 most distinctly sensible, are especially the movements affecting 

 joints ; indeed we have some difficulty in appreciating the 

 amount and character of a movement not necessarily involv- 

 ing a joint such as one caused by contractions of the orbicu- 

 lar muscle of the mouth or of the eye, even though in these 

 cases we are assisted by cutaneous sensations. 



We have evidence both that the joints and that the mus- 

 cles can supply the necessary afferent impulses. The joints are 

 well supplied with afferent nerve fibres, and undoubtedly give 



