ii SENSIBILITY OF THE INTERNAL ORGANS 105 



weights raised were not perceptibly altered when the movement 

 was excited by the electrical stimulus. From these experi- 

 ments it was concluded that the supposed sense of innervation 

 does not exist, because the muscular sense is adequate to subserve 

 the estimation of the differences in weight. 



On closer investigation, however, these experiments, which 

 otherwise gave no constant results, only show that in judging 

 weights the sense of effort, due to the resistance which the 

 muscles encounter in lifting the weight, is more important than 

 that of the central innervation sense, which we are compelled to 

 admit on other irrefutable grounds. 



(c) The third objection to the sense of innervation is drawn 

 from the fact that independently of sensations of peripheral 

 origin we are not able to prove any direct and unmistakable 

 central sensations of innervation. Ferrier more particularly uses 

 this argument in opposing the theories of Bain and Wundt : 



" If the reader will extend his right arm and hold his fore- 

 finger in the position required for pulling the trigger of a pistol, 

 he may without actually moving his finger, but by simply making 

 believe, experience a consciousness of energy put forth. Here, 

 then, is a clear case of consciousness of energy without actual 

 contraction of the muscles either of the one hand or the other, 

 and without any perceptible bodily strain. If the reader will 

 again perform the experiment, and pay careful attention to the 

 condition of his respiration, he will observe that his consciousness 

 of effort coincides with a fixation of the muscles of his chest, and 

 that in proportion to the amount of energy he feels he is putting 

 forth, he is keeping his glottis closed and actively contracting his 

 respiratory muscles. ... In the contraction of the respiratory 

 muscles there are the necessary conditions of centripetal impres- 

 sions, and these are capable of originating the general sense of 

 effort." 1 



This objection is eas}^ to meet. If the feeling of innervation 

 is to coincide with the motor impulse, that is with the centrifugal 

 wave of excitation sent out along the motor paths, it must 

 obviously be absent when we imagine that we send it out, but do 

 not really do so. The whole of Ferrier's reasoning merely shows 

 that the sense of innervation cannot function unless there is 

 a simultaneous muscular contraction, so that it is impossible to 

 separate the sensations of central from those of peripheral origin. 

 But this does not refute the theory of a sense of innervation if 

 other powerful arguments speak in its favour. 



On the other hand, it may legitimately be maintained that the 

 central sensations of innervation, particularly in habitual move- 

 ments, normally lie beneath the threshold of consciousness. The 

 same may be said of the sensations of peripheral origin that 



1 Ferrier, The Functions of the Brain, 1876, p. 2'23. 



