140 ANNUAL OP SCIENTIFIC DISCOVERY. 



become longer from the influence of the sight upon the muscular or- 

 gan ; and this, too, without our having the consciousness of it. This 

 is the second fact. 



" The tendency to motion, determined in us by the sight of a body 

 in motion, is found in several cases. For example: 



" 1. When the attention is wholly fixed upon a bird flying, a stone 

 thrown, running water, the body of the spectator is directed more or 

 less towards the line of motion. 



4i 2. When a billiard player follows with his eye the ball he has 

 just put in motion, he places his body in the position he would see the 

 ball follow, as if it was still possible for him to direct it towards the 

 mark whither he sought to direct it. 



" When we walk upon a slippery place, everybody knows with 

 what promptness we throw ourselves on the side opposite to that 

 whither our body is carried in consequence of losing its equilibrium ; 

 but a circumstance less generally known is, that a tendency to the 

 motion appears even when it is impossible for us to move in the sense 

 of this tendency. For example, in a carriage the fear of being upset 

 makes us lean in a direction opposite to that which menaces us, and 

 from it result efforts which are so much the greater as the fright and 

 irritability are greater. I believe that, in ordinary falls, the falling is 

 less painful than the effort made to prevent the fall. It is in this 

 sense that I understand the justness of the proverb : II y a un Dieu 

 pour les enfans et pour les ivrognes ! 



" The tendency to motion in a determined sense, resulting from the 

 attention given to a certain object, seems to me the prime cause of 

 several phenomena generally ascribed to imitation. Thus when we 

 have seen or have heard a person gape, the muscular motion of gap- 

 ing generally takes place in us in consequence. I may make the 

 same remark about the communication of laughter, and, besides, this 

 example presents more than any other analogous one, a circumstance 

 which seems to me to support the explanation I have given of these 

 phenomena. For laughter, feeble at first, may, if kept up, become 

 accelerated (pardon the word) as we saw the oscillations of the pen- 

 dulum held in the hand augment in amplitude, influenced by the 

 sight ; and laughter, in being accelerated, may go to convulsions. 



" I do not doubt but that the sight of certain actions proper, so act 

 forcibly upon our frail machine, that the relation of these same ac- 

 tions animates with the voice or gesture ; or, further, the knowledge 

 communicated of them by merely reading about them does not induce 

 some individuals to do these very same actions, in consequence of a 

 tendency to motion, which thus mechanically determines them to an 

 act of which they never would have thought, had not some circum- 

 stance, extraneous to their will, presented it, and to which they would 

 never have been led, but by that which we call instinct in animals. 



" In here terminating the exposition of facts which seem connected 

 with my observations, I think I should make a remark which is cer- 

 tainly contained in the foregoing paragraphs, but which may escape 

 some reader : it is, that this tendency to motion, to which I attribute 



