240 LETTERS TO BROTHER JOHN. 



should be just sufficient to restore to the blood 

 what the blood has lost in restoring the waste of 

 the body, and that it should always be proportioned 

 to the degree of bodily exertion undergone. 



You might here very properly inquire, how we 

 are to know the exact amount of this daily waste, so 

 as to apportion the quantity of food thereto. Are 

 we to weigh ourselves every morning, in order to 

 ascertain this important fact ? No, my dear John : 

 Nature has not left any part of her master-miracle 

 incomplete ; which it would have been, assuredly, 

 had she not provided us with infallible means of 

 knowing, not only when, but how much, we ought to 

 eat and drink. 



When you are excessively thirsty, and when you 

 are in the act of quenching your thirst with a 

 draught of cold water (which I shrewdly suspect is 

 but seldom), tell me, How do you know when you 

 have drunk enough? One token, by which you 

 know this, is, the cessation of thirst; and this, of 

 itself, should be sufficient; and, in truth, so it is, 

 when you drink water > I dare say. But there is 

 still another ; and one which not only informs you 

 when you have drunk enough, but which also pre- 

 vents you from drinking more. While you are in 

 the act of drinking, and before your thirst has been 



