68 LIFE. 



totally different category. Physical and chemical actions 

 may be investigated in many ways, but as far as we can 

 judge, the last class of actions (vital) seems to be beyond 

 investigation, and has not yet been satisfactorily accounted 

 for. If we regard the life of a man, as the sum of all 

 the actions going on in his body, as some are inclined 

 to do, the sum will be made up of a number of very 

 different and heterogeneous items. To sum up these 

 together and express the result in a common total would be 

 as unmeaning as it would be to add ounces to shillings 

 and inches. By the " life " of a white blood corpuscle or 

 other small mass of living matter we mean the property or 

 power or conditions to which the phenomena, characteristic 

 of this and other kinds of matter in the same state, are 

 referable. 



Here then are three distinct senses in which the term 

 life has been employed, and more might be adduced. It 

 must, therefore, be obvious that by the life of a man some- 

 thing very different is understood from what is meant by 

 the life of each elemental unit of his organism, and the 

 difference is not merely of degree but of kind. 



We cannot prove that life results from, or is invariably 

 associated with such and such chemical and physical changes, 

 or is due to certain external conditions, and it is easy to ad- 

 duce instances in which life is present under opposite and 

 conflicting circumstances. In short the conditions under 

 which life exists are so many and so variable that it is not 

 reasonable to attribute it to any conceivable combinations 

 of external circumstances unless we may assume that the 

 very same phenomena result from the concurrence of very 

 different conditions. 



