THE NATURE OF MUSCULAR SENSE. 1005 



But there are differences in the effect of anaesthesia on motor power. In some 

 cas es the anaesthetic patients cannot move their limbs at all ; in some they 

 cannot move them when their eyes are shut. 1 In some, accurate movement is 

 only possible by help of visual perceptions ; with closed eyes ataxy becomes 

 extreme. But there is a class of cases in which, although a limb has lost all 

 sensitivity even for passive movement, voluntary movements can be accurately 

 executed even when the eyes are closed. The patients can, for example, write 

 accurately at will although their eyes are closed, and though they have no 

 feeling of the writing taking place, and do not know when it begins or stops. 2 

 This class is formed of hysterical and hypnotic cases. At first sight these 

 examples furnish the strongest evidence in favour of the " feeling of innerva- 

 tion " view. No other guiding impressions resident or remote appear to exist. 

 Appeal to the speaking intelligence of the patient does not give evidence of 

 any. But those who have especially studied these cases urge that the 

 condition is not one of true or physiological anaesthesia. They regard these 

 patients as victims of divided consciousness ;, a part of their consciousness 

 containing, for instance, the kinaesthesia of a limb or lateral part of the body, 

 becomes split off from the remaining consciousness. In the split-off part the. 

 kinaesthetic impressions and sensations may nevertheless remain to produce 

 their usual effects, including co-ordination of movement. 



The thumb and the three outer fingers are kept fully extended by pressing 

 their tips down on a table edge, and the index is flexed fully except at its end 

 joint, at which, under the circumstances, flexion is mechanically impossible. 

 If, then, the effort to flex the end be made without looking at the finger, most 

 persons believe the movement intended is carried out. The peripheral sensa- 

 tions of the existing position are overcome by those of the flexed position 

 revived for the initiation of willed movement. 3 Similarly, Exner's illusion, — 

 biting on an unyielding plate giving sense of penetration, although no move- 

 ment is really effected. Loeb's i interesting observations on willed movements 

 seem to me to illustrate rather that two simultaneous movements are not, 

 when asymmetrically placed, appreciable very delicately in regard to extent 

 and direction, and that judgment of them is easily biassed by the precurrent 

 kinaesthetic idea revived in the willing of the movement. They seem to me 

 to show a somewhat surprising deficiency in muscular sense working under 

 certain conditions, but not to prove that that sense is based on " feeling of 

 innervation," still less to disprove that it is based on centripetal impressions 

 excited in the acting peripheral organs during the movement. 



Our conclusion is therefore that " sensation of innervation " — pro- 

 vided that memory revivals of muscular sensations of peripheral origin 

 be not included under that term — remains unproven. Many psycholo- 

 gists argue for it ; many, however, do not accept it. 5 



A second view held regarding " muscular sense " considers it to 

 result from sensations derived from the sense organs of the other " five 

 senses," and to have, strictly speaking, no apparatus of its own. 

 Changes in tension of the skin (Schiff) at flexures, etc., are reported by 

 the cutaneous afferent nerves, and yield perceptions of the movements 

 they accompany, of postures, etc. The delicacy of the " five senses " 

 is such that in unsuspected ways they make us aware of the effects 

 of even minute movements (Hensen). A grave objection to this view 



1 Bastian, Brain, London, 1887, vol. x. p. 1 ; Binet, Rev. phU., Paris, tome xxv. p. 478. 



2 Charcot, " (Euvres completes," Paris, tome iii. p. 467. 



3 It is right to state that this is not the interpretation of the experiment submitted by 

 Dr. Sternberg, who devised it ; he regards it as evidence of "sensation of innervation." 



4 Arch./, d. ges. Physiol., Bonn, 1890, Bd. xli. ; also 1892, Bd. xlvi. 



b Bastian, Brit. Med. Journ., London, 1809, vol. i. p. 461 ; James, op. cit.; Miinster- 

 berg, op. cit. 



6 "Gegen den sechsten Sinn," Berlin, 1893. 



