334 THE POPULAR SCIENCE MONTHLY. 



logical psychology is the theory of the muscular sense. Destutt 

 de Tracy maintained that without motion we could not have 

 knowledge of the existence of bodies ; for it is arrested movement 

 that gives the sensation of resistance. The essential point in the 

 theory is to distinguish the sense of effort from purely passive 

 muscular sensations. If consciousness is a good judge in these 

 matters, says Alexander Bain, we may say that in voluntary effort 

 we have the feeling of a faculty experienced from within out- 

 ward and not that of a sensible surface stimulated by an external 

 agent and transmitting an impression from without to within the 

 nervous centers. The sense of effort would then seem to be the 

 feeling of the production of motion rather than of motion pro- 

 duced. It is anterior' and not posterior to the motion. Without 

 going into detail, we can, according to Bain, refer all muscular 

 sensations to two great classes : the sensation of tension, and that 

 of motion. Tension is an act of effort in so far as it meets an 

 invincible resistance, for example when it endeavors to raise a 

 weight that is beyond its strength, or to stop a galloping horse. 

 "We can distinguish three distinct sensations in that of tension : 

 pressure, traction, and weight. The first occurs when we wish to 

 crush an object, as a nut, with the hands ; the second, when we 

 wish to lead an object, as a horse, or a man who is resisting us ; 

 and the third, when we lift a weight. The first is an effort of 

 ourselves on the exterior object ; the second, of the exterior object 

 on us ; and the third, an upward effort. The feeling of tension is 

 the same, whether the extensor or flexor muscles are involved. It 

 is in a certain manner the feeling of force in equilibrium with 

 the exterior force, but at its limit, and unable to go farther. 



It is surprising that Bain, in discussing what he called the 

 sensation of motion, did not first ask if such a sensation exists. 

 Without doubt, since we effect motion, there must be something 

 in the consciousness that corresponds to it ; but does that some- 

 thing resemble what we call a motion — that is, a displacement in 

 space ? We see that the question of the sensation of motion is 

 closely bound with the idea of the perception of space, or with 

 the most obscure and complex question of metaphysics. Without 

 this notion of space, the muscular sensation could not even take 

 the name of tension or of contraction, for these terms imply mo- 

 tion, and motion implies space. The only peculiar characteristic 

 of muscular sensation appears to be fatigue. Effort is an internal 

 fatigue distinct from the external fatigue which is imposed by 

 causes foreign to us. It consists in giving one's self a fatigue by 

 the production of a desired act. We thus see how apparently the 

 most elementary questions are complicated with those of the high- 

 est order. What, for example, is a desired act ? The study of the 

 simplest sensation, therefore,, involves a theory of the will. 



