LETTERS TO BROTHER JOHN. 115 



when distended with water than when dry ; since, 

 when dry, its cells are filled with air; but when 

 saturated with water, they are filled with water, 

 which is a far more compact material than air. If 

 you draw a thread through a sponge saturated with 

 water, the sides of that thread will be everywhere 

 compressed and supported by either the solid parts 

 of the sponge or by the water : whereas, if you 

 draw a thread through a dry sponge, whenever that 

 thread passes through an empty cell its sides will 

 be entirely unsupported and uncompressed. So of 

 the body; a nerve passing through the body (which 

 body consists of a congeries of vessels) will have its 

 sides everywhere compressed and supported, so long 

 as those vessels are well filled and fully distended. 

 But if these vessels be half empty if their sides be 

 allowed, as it were, to collapse and fall away from 

 the nerves which they everywhere surround it is 

 manifest that those nerves will not be so firmly 

 compressed and well supported as they were while 

 all the vessels surrounding them were fully dis- 

 tended. It is this half-filled state of the vessels 

 which constitutes that lax and soft state of the body 

 called flabby. This loose, flabby, and uncompact 

 state of the body, therefore, is highly favourable to 

 SENSIBILITY ; since SENSIBILITY is always increased 



