222 LETTERS TO BROTHER JOHN. 



is the blood : but this is by no means the only one. 

 There are many others; such as, light, heat, elec- 

 tricity, and the excitement produced through the 

 medium of our organs of hearing and seeing, &c. : 

 but, besides these, there are also others. And what 

 are these others, my dear John? Why, precisely 

 the very circumstances of our natural existence 

 which are now under discussion : I mean, the very 

 self-same "discomforts" aforesaid. They form 

 a part of the necessary and natural stimuli. As 

 " comfort " (that is, the absence of all " discom- 

 fort ") has the effect of lulling the system to sleep 

 and sloth ; so " discomfort," which is the opposite 

 of " comfort," produces an opposite effect ; viz. that 

 of rousing the system to energy and action. He 

 who sleeps on the hill side, unsheltered, is not likely 

 to sleep too long. 



It was ordained that the human heart should 

 continue to pulsate for a certain number of years. 

 In order to accomplish this, it was necessary to 

 afford to it a perpetual supply of stimulus, to a given 

 amount. If the blood alone were capable of sup- 

 plying this necessary given amount, then, when the 

 being to whom this heart belonged came to be 

 placed in the world which he was destined to in- 

 habit, and within the operation of these other stimuli, 



