82 LETTERS TO BROTHER JOHN. 



As vitality is. not life, then, so neither is it orga- 

 nism, but merely a condition of the latter, neces- 

 sary to the existence of the former. Life, then, 

 being neither organism nor vitality, what is it ? 



" Life," says Richerand, " consists in the aggre- 

 gate of those phenomena which manifest them- 

 selves in succession for a limited time in organized 

 beings." 



" Life," says Dr. Fletcher, in one of the most 

 erudite, elegant, and ingenious works that ever fell 

 from the press " life consists in the sum of the cha- 

 racteristic actions of organized beings, performed 

 in virtue of a specific susceptibility (vitality), acted 

 up on by specific stimuli." These two definitions are 

 perfectly consentaneous with each other ; and to 

 them I have nothing to add. Life, like death, is 

 not an entity : it is merely an aggregation of 

 effects. To say what life is, is only to enumerate 

 all the actions of which a living being is capable ; 

 not only the visible actions, as of the members, but 

 also the molecular actions, as those invisible motions 

 among the proximate molecules of the matter of 

 which he is composed, and by which his nutrition 

 is effected. Life is, to organism, contractility, 

 sensibility, and stimuli, what chemical phenomena 

 are to chemical affinity what astronomical pha?no- 



