PROFESSOR WHEWELL, ON CAUSE AND EFFECT. 327 



if it were not to take food ; and that food is the cause of a change, 

 namely, of growth ? This is manifestly false ; for if the animal were 

 not to take food, it would soon perish. But the analogy of the former 

 case, of the clock, will enable us to avoid this perplexity. As we assumed 

 a steady rate of going in the clock to be the measure of time when 

 we considered the effect of mechanism, so we assume a steady rate of 

 action in the animal functions to be the measure of the progress of 

 time when we consider the causes which act upon the development 

 and health of animals. Digestion, and of course nutrition, are a part 

 of this normal condition ; they are involved in the steady going of the 

 animal mechanism, and we must suppose these functions to go regularly 

 on, in order that the animal may preserve its character of animal. Food 

 and digestion may be considered as causes of the continued existence of 

 the animal, in the same way in which the form of the parts of a clock 

 is the cause of the steady going of a clock. And when we come to 

 consider causes of change, this kind of causation, which produces a normal 

 condition of things, merely measuring the flow of time, is left out of our 

 account. We can conceive an uniform condition of animal existence, the 

 animal neither growing nor wasting. This being taken as the normal condi- 

 tion, any deviation from this condition indicates a cause, and is taken as the 

 evidence and measure of the cause of change. And thus, in a growing animal, 

 the food partly keeps the animal in continued animal existence, and partly, 

 and in addition to this, causes its growth. Food, in the former view, is 

 always circulating in the system, and is supposed to be uniformly adminis- 

 tered ; the cycles of nutrition being merged in the notion of uniform 

 existence, as the oscillations of the pendulum in a clock are merged in 

 the notion of uniform going ; and the elementary steps of nutrition which 

 are, in this view, supposed to take place at each instant, produce their in- 

 stantaneous effect, for they are requisite in the cycle of animal processes 

 which goes on from instant to instant. But on the other hand, in con- 

 sidering growth, we compare the state of an animal with a preceding 

 state, and consider the nutriment taken in the intervening time as the 

 cause of the change : hence this nutriment, as an aggregate, is considered 

 as the cause of growth of the animal; and in this view the effect is 

 subsequent to the cause. But yet here, as in the case of mechanism, 



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