18 LIFE IN NATUKE. 



the living body and the machine has not been sooner 

 recognized. The processes of nature are studied by 

 us in au inverse order: we see effects before we 

 discover causes. And such is the deadening effect 

 of familiarity upon our minds, that the seen effect 

 has often ceased to excite our wonder, or stimulate 

 our demand to know a cause, before the discovery of 

 that cause is made. 



But there is yet a third reason for the difficulty 

 that has been found in solving this problem of the 

 nature of the animal functions. It is complicated by 

 the co-existence, with the functional activity, of many 

 other and different processes. The body is at the 

 same time growing and decaying; it is nourished while 

 it is dying. The web of life is complex to an un- 

 paralleled degree. Well is the living frame called a 

 microcosm ; it contains in itself a representation of 

 all the powers of nature. It cannot be paralleled 

 by any single order of forces ; it exhibits the inter- 

 working of them all. And those processes of de- 

 composition which generate functional activity are 

 so mixed up with other vital processes, that no 

 experiment can disentangle them. The relations of 



