130 EVOLUTION, OLD AND NEW. 



writes Buffon, "the pleasantness or unpleasantness, 

 because this is the very essence of perception ; the one 

 feature of perception consists in perceiving either pain 

 or pleasure ; and though movements which do not affect 

 us in either one or the other of these two ways may 

 indeed take place within us, yet we are indifferent to 

 them, and do not perceive that we are affected by them. 

 All external movement, and all exercise of the animal 

 powers, spring from perception ; its action is proportion- 

 ate to the extent of its excitation, to the extent of the 

 feeling which is being felt.* And this same part, which 

 we regard as the centre of sensation, will also be that 

 of all the animal powers ; or, if it is preferred to call it so, 

 it will be the common point d'appui from which they 

 all take rise. The diaphragm is to the animal what the 

 ' stock ' is to the plant ; both divide an organism trans- 

 versely, both serve as the point d'appui of opposing 

 forces ; for the forces which push upward those parts of 

 a tree which should form its trunk and branches, bear 

 upon and are supported by the ' stock/ as do those 

 opposing forces, which drive the roots downwards. 

 ****** 

 " Even on a cursory examination we can see that all 

 our innermost affection?, our most lively emotions, our 

 most expansive moments of delight, and, on the other 

 hand, our sudden starts, pains, sicknesses, and swoons 

 in fact, all our strong impressions concerning the plea- 

 sure or pain of any sensation make themselves felt 

 within the body, and about the region of the diaphragm. 

 The brain, on the contrary, shows no sign of being a seat 

 * Tom. vii. p. 12, 1758. 



