LETTERS TO BROTHER JOHN. 113 



unhealthy degree of SENSIBILITY to the natural 

 standard. This can be easily done; so easily, that 

 I will undertake, within one month, without fee or 

 reward, or pill or potion of any kind, and on the 

 peril of my head, to enable any lady within the 

 pale of the United Kingdom of Great Britain 

 and Ireland to carry a bushel of potatoes on her 

 head from Pedlar's Acre to Penny-Fields without 

 resting, and that with no more pain and labour to 

 herself than may be sufficient to spare her pocket 

 the expense of sixpenny-worth of rouge. 



Now, then> it is quite clear, that whatever causes, 

 circumstances, regimen, or conduct, have a tendency 

 to heighten SENSIBILITY, must necessarily have a 

 tendency to depress CONTRACTILITY ; since I have 

 proved that a high degree of the former is wholly 

 incompatible with a high degree of the latter, and 

 therefore cannot exist in conjunction with it. 



The reason why a high degree of SENSIBILITY 

 cannot exist in conjunction with a high degree of 

 CONTRACTILITY is this : the nerves (which are the 

 seat of sensibility) are more or less acutely sensible, 

 according to the greater or less degree of firmness 

 with which they are compressed on all sides by the 

 parts immediately surrounding them and in contact 

 with them. Thus the nerves of the bones, ligaments. 



