APPENDIX. 699 



ataxy ' the amount of symptoms indicative of a diminution in the 

 so-called ' muscular sense ' was generally proportionate to the im- 

 pairment of the different modes of common sensibility in the limb. 

 Yet some more exceptional cases of this disease recorded by 

 Bazire, Trousseau and others, as well as some remarkable cases 

 referred to by Landry, in which, without the existence of ancesthesia, 

 the patients were reduced to a condition very similar, as regards 

 motility and the sensations resulting from movement, to that of 

 Demeaux's patient, seemed to show pretty conclusively "that the 

 brain is assisted in the execution of voluntary movements by guid- 

 ing impressions of some kind, which, whilst they differ in mode of 

 origin from the impressions derivable by means of the ordinary 

 cutaneous and deep sensibility, may differ still further from these, 

 owing to the fact of their not being revealed in consciousness* . . . . 

 There is clearly a loss of something in these cases, of a something 

 which serves as a guide in the execution of voluntary movements, 

 but whose absence can be compensated by the supervision of the 

 visual sense; and this is in great part the function which some 



physiologists attach to the 'muscular sense' my position 



is that these impressions of the muscular sense, whose existence 

 we are thus obliged to postulate, are unconscious impressions, 

 and that the conscious impressions that have usually been stated 

 to fall within its province are really derivable through modes of 

 ordinary cutaneous and deep sensibility." 



The conclusions thus deduced in 1869, are fully borne out by 

 what we now know concerning Hemi- anaesthesia of cerebral origin. 

 The instance recorded by Demeaux is altogether exceptional, since 

 in many of such cases complete superficial, and in some even deep 



* The route of these afferent impressions at the commencement and towards 

 the end of their course -was then wholly unknown. And in face of difficulties 

 presented by evidence adduced by Arnold, the writer hazarded the following 

 conjecture: "Thus I assume it to b9 possible that when molecular changes are 

 excited in certain spinal motor cells as a result of a volitional impulse, proportional 

 recurrent impressions may be carried along certain fibres taking origin from tLe 

 niutor cells, and ascending in the posterior columns of the cord." In this way 

 the brain might derive impressions referrible to the degree of activity of the 

 various muscles, or sets of muscles, of a limb. But our present increased knowledge 

 concerning the existence of 'sensory' nerves in muscle, no longer renders necessary 

 any such hypothesis, especially as the writer is now inclined to agree with Ferrier 

 in his interpretation ('Functions of the Brain,' p. 220) of Arnold's experiments. He 

 thus no longer feels any difficulty in believing that some of the sensory fibres of 

 muscles which enter the spinal cord by the posterior roots of the spinal nerves, may 

 transmit to the brain those almost ever-present ' unconscious ' impressions which 

 BO materially guii 3 us in the execution of all our movements. 



