METHODS 47 



plants and also in animals, provided that we study the latter 

 not at the very special moment when they are adults, but 

 during the first time of their individual existence precisely 

 during what is called their period of growth. The calf grows 

 and becomes a bull, the kid grows and becomes a goat, the 

 child grows and becomes a man. 



But you will say that the snowball grows by rolling, the 

 alum crystal grows in a solution of alum, and yet we do not 

 consider the alum crystal and the snowball living ! 



The case is not the same, for the alum crystal grows at 

 the expense of a solution of alum, the snowball grows at the 

 expense of a layer of snow, whereas the calf grows by eating 

 hay, clover or lucern. In other words, the animal or plant 

 develops at the expense of substances different from its 

 own, whereas in the cases of growth observed in not-living 

 bodies the increase in size is at the expense of substances 

 identical with that which grows (or, at least, by means 

 of elements which are always the same ; for example, in 

 the case of carbonate of lime which, at the temperature of 

 dissociation, may increase under the influence of increased 

 pressure at the expense of carbonic acid and lime). 



Here, then, is a character which seems common to all 

 living bodies, at least during a portion of their life. 



It must be acknowledged that this character presents 

 itself to us in very crude outlines ; man is a grown-up child, 

 but how different from the child ! The bull is a grown-up 

 calf, but not only his form, his substance even, his flesh, 

 seem to us very different from the form and flesh of the calf. 

 So we perceive how approximate only is this result : the calf 

 from grass and lucern and clover produces the substance of 

 the calf. 



Yet beneath this crude proposition lies concealed the 

 character by which we shall define life. It will be easier 



