ioo 4 THE MUSCULAR SENSE. 



when the movements are brought about by direct faradisation of the nerve 

 trunks and muscles. 1 The liminal difference is, however, then much greater 

 than under volition. It is less under faradisation of the nerve than under 

 galvanisation of the nerve, and less under galvanisation of the nerve than of 

 the muscle ; but even with nerve faradisation it is 2 '5 times greater than with 

 volition. Waller l considers this amount of discrimination no greater than can 

 be accounted for by touch alone. 



Wundt, when upholding the " sensation of innervation," appealed to the 

 " heaviness " of a paretic limb. But it can be replied that a paretic limb feels 

 heavy because its movements are hampered as when weighted. Yulpian and 

 also Terrier 2 have pointed out that when a hemiplegic patient tries to close 

 his paralysed hand, he in his endeavour, without willing to do so, performs 

 the action with the sound one. The muscles of the glottis and the respiratory 

 muscles invariably become active under effort ; as the effort increases, its motor 

 discharge becomes more and more diffuse. 



A phenomenon cited by Helmholtz is the following : " When the right 

 external rectus is paralysed, the right eye can no longer rotate to the right. 

 So long as it turns only to the nasal side it makes regular movements, and the 

 correct position of objects is perceived. When it should be rotated outwardly, 

 however, it stays still in the primary position, and the objects appear flying to 

 the right, although the position of eye and retinal image are unaltered." The 

 left sound eye is covered. "In such a case," Helmholtz 3 goes on to say, "the 

 exertion of the will is followed neither by actual movement of the eye, nor by 

 contraction of the muscle in question, nor even by increased tension in it. The 

 act of will produced absolutely no effect beyond the nervous system, and yet 

 we judge of the direction of the line of vision, as if the will had exercised its 

 normal effects. We believe it to have moved to the right, and, since the 

 retinal image is unchanged, we attribute to the object the same movement we 

 have erroneously ascribed to the eye. . . . These phenomena leave no room 

 for doubt that we only judge the direction of the line of sight by the effort of 

 will with which we strive to change the position of our eyes. . . . We feel, 

 then, what impulse of the will, and how strong a one, we apply to turn the 

 eye into a given position." But the interpretation neglects (G. E. Miiller, W. 

 James) the movement of the covered eyeball as a source of peripheral 

 sensation. 



I^ot only is evidence of sensation of innervation unconvincing, but facts it 

 fails to explain are explicable by the counter view of peripheral sense organs. 

 Of a patient in which the entire arms and trunk down to the navel were 

 insensible, superficially and deeply, but the arms not paralysed, it was noted as 

 follows : "We 4 take three bottles, two empty weighing 250 grms. each, the 

 third full of Hg and weighing 1850 grms. The patient declares he finds 

 them all weigh alike. An experiment was performed, in which he could be 

 informed neither by sight nor by hearing. He even declared, holding in his 

 hand the bottle full of mercury, that he found it have no weight. We place 

 successively in his hand (his eyes bandaged), a piece of modelling wax, a stick 

 of wood, a thick rubber tube, and newspaper folded lengthwise. These he 

 squeezes. He feels no difference of resistance ; he does not even perceive that 

 anything is in his hand." 



1 Bernhardt, Arch. f. Psychiat., Berlin, 1872, Bd. iii. S. 618 ; Ferrier (and Brunton), 

 "The Functions of the Brain," 1876, and 2nd edition, 1886; Waller, Brain, London, 

 1891, vol. xiv. ; and " Proc. Phys. Soc.," Journ. Physiol., Cambridge and London, 1892, 

 vol. xiii. 



2 "Functions of the Brain," 1876, p. 227. 



3 I quote from W. James' translation in "Principles of Psychology," vol. ii. p. 507, 

 which is from the 1st edition of the "Physiol. Optik." The passage remains unaltered in 

 the 2nd edition, p. 744 (1896), which is a part of the volume lying beyond that revised by 

 Helmholtz before his last illness. 



4 Gley et Maxilier, trans, by W. James, Rev. phil., Paris, tome xxiii. p. 442. 



