LETTERS TO BROTHER JOHN. 267 



a perpetual replacement of them by new by perpe- 

 tual disorganization, and perpetual re-organization. 



The operation by which life is supported may 

 be illustrated by the operation by which motion is 

 supported and communicated by two wheels acting 

 on each other. Keep your eye steadily fixed upon 

 the point at which the cogs of the two are inter- 

 locked. What do you observe ? Why, that, at 

 every instant, the empty space which is presented 

 by one wheel, is instantly filled up by a tooth of 

 the other wheel to be almost instantly emptied 

 again, and again re-filled. Thus it is, that, at 

 every point of the body, and at every instant, the 

 absorbents are making little empty spaces ; which 

 are immediately filled by the nutritive arteries, to 

 be again emptied by the absorbents, and again 

 filled by the arteries. 



Another postulate, necessary to my forthcoming 

 argument, and which is also indisputable, is this, 

 that you cannot increase the size of your natural 

 body, the substance of your natural fibre, by eating. 

 This is certainly true. For if it were otherwise, 

 the magnitude of the body would be equally 

 enlarged at every point. If you increased its 

 transverse diameter, you must also increase its 



longitudinal diameter. You could not make it 



N2 



