THE NATURAL HISTORY OF REST 327 



the power of taking rests. This is part of their essential 

 secret. Conversely, the man who loses the power of taking 

 rest becomes a machine. 



We must not, of course, think of the need for taking 

 rests as in any way a new need, which has arisen in a 

 restless age. The need for rest is primitive, and the resting 

 habit has its roots in the remotest past, and its reason in 

 the nature of things. 



The argument is obvious and trite. Since all activity, 

 mental as well as bodily, emotional as well as intellectual, 

 involves expenditure of energy, the rate of work must 

 periodically diminish, there must be relative rest, there 

 must be time for the most primitive form of rest which 

 consists in re-stoking the living engine. There are some 

 minute unicellular animals which are said to continue to 

 move about as long as the store of a certain substance 

 within their cell holds out. When that store is exhausted 

 their motor activity is at an end for the time being. Before 

 it begins again, they must accumulate more fuel for the 

 living fire. Here the conditions of rest are seen in their 

 simplest expression. There must be at least a rest for 

 eating but we do not need to go far to see how much 

 even this is grudged by " the Minister and Interpreter of 

 Nature." 



Other needs for rest have gradually arisen. There 

 must be time for the fuel to warm up, for the food to become 

 thoroughly available. But there is much more than this. 

 The activities of daily life, including the stoking itself, 

 involve wear and tear of the vital machinery. There must 

 be rest for repair. In the simplest animals this wear and 

 tear is reduced to a minimum, or the repair is approximately 

 perfect, so that little rest is required. They do not seem 

 even to need to die. In more complex animals, however, 

 the wear and tear is greater as life becomes fuller, the 



