104 PHYSIOLOGY CHAP. 



seems to admit these logical conclusions. For, in the 5th edition 

 of his Analysis of Sensations, he inclines if not directly joining 

 with those who admit the sense of innervation at least to leave 

 the question open. 



We must now turn to the fundamental arguments of the 

 opponents of a sense of innervation, including the psychologists 

 William James and Miinsterberg, and the majority of living 

 physiologists. They may be reduced to three main propositions, 

 which we will consider in turn : 



(a) The first objection to the theory of a sense of innervation 

 is derived from the clinical case recorded by Striimpell, quoted 

 above (p. 90). In this case the motor paths are intact, because 

 with the aid of vision the patient is perfectly able to carry out 

 any movement at command. The paths from the hand and fore- 

 arm, of both superficial and deep sensation, are, on the contrary, 

 completely interrupted. The conditions for the so-called innerva- 

 tion sense are therefore intact, while those for the muscular sense 

 are interrupted. Seeing that with his eyes shut the patient is 

 unaware of the flexed or extended position of his fingers, is unable 

 to maintain the position of the hand assumed when his eyes were 

 open, or to carry out correctly the movements he is told to 

 perform, there is here sufficient reason for denying the existence 

 of a special central sense of innervation. 



The force of this objection is undeniable. It does not, how- 

 ever, seem to us to cancel the weight of the above arguments in 

 favour of a sense of innervation. We have seen that there are 

 exceptions to the fact that amputated persons are " aware " of the 

 lost limb, and that still more frequently they are unable to move 

 the joints imagined in it. Strumpell's case, which deals not with 

 an arm amputated in toto, but merely with interruption of the 

 sensory paths, may count as one of these exceptions. In any case 

 it shows that integrity of the motor paths is not enough to secure 

 perfect execution of voluntary movements, and that we do not 

 yet know all the internal conditions necessary to the normal 

 functioning of the sense of innervation. 



(&) The second objection is founded on certain experiments of 

 Bernhardt (1872), subsequently confirmed by Goldscheider. In 

 order to decide whether in judging of the weight of a body we 

 employ the peripheral muscular sensations only, or a central sense 

 of innervation as well, Bernhardt made comparative experiments 

 and used alternately, in lifting weights, a voluntary contraction 

 and a contraction produced by a direct electrical stimulus. In a 

 first series of researches made on the muscles of the leg he saw 

 that the difference between two weights is less well distinguished 

 when the muscular contraction is produced electrically. But in a 

 second series of experiments on the flexor muscles of the fingers 

 he no longer found the same difference, and the judgments of the 



