LETTERS TO BROTHER JOHN. 143 



in the manner which I described when speaking 

 of the circulation of the blood. Here the final 

 change is effected; and that which was bread and meat 

 has now entirely lost all its former characteristics. 

 It was first food, then chyme, then chyle. Now it 

 is none of these : it has acquired, by virtue of the 

 agency of the air in the lungs, the colour and all 

 the other qualities and properties of blood : in a 

 word, it has become blood itself. Thus, comparing 

 the animal economy to the economy of vegetable 

 life, one might say, that the stomach and bowels are 

 the soil; the food is the seed which is sown therein ; 

 and blood is the fruit which that seed produces a 

 fruit which is destined to become the food of the 

 animal. For, as was justly said by Hippocrates-, 

 " there is but one food, although there are several 

 forms of food." However various the v iands may 

 be which we put into the stomach, they must all be 

 converted into one and the same fluid, viz. blood, 

 before they can have any effect whatever in 

 nourishing or strengthening the body. Blood, 

 then, is the sole nourishment on which we subsist ; 

 the food which we eat being no more than so much 

 seed sown, with the view of producing a nutritious 

 fruit, by which the body is to be/ec/, and its health 

 and strength sustained ; viz. blood. We are no 



