LIFE. In seeking a definition of life, it is difficult to find one that does not include more than is necessary, or exclude something that should be taken in. Rieherand's definition of life, that it is "a collection of phenomena which succeed each other during a limited time in an organized body," is equally applicable to the decay which goes on after death. According to De Blainville, "life is the twofold internal movement of composition and decomposition, at once general and continuous." As Mr. Herbert Spencer in his Principles of Biology well observes, this conception is in some respects too narrow, and in other respects too wide. Thus, it excludes those nervous and muscular functions which form the most conspicuous and distinctive classes of vital phenomena, while it equally applies to the processes going on in a living body and iu a galvanic battery. Mr. Spencer (in 1852) proposed to define life as the " co-ordination of actions," but as he observes, "like the others, this definition includes too much, for it may be said of the solar system, with its regularly recurring movements and its self-balancing perturbations, that it also exhibits co-ordination of actions." His present, and amended
conception of life is: - The definite combination of heterogeneous changes, both simul taneous and successive, in correspondence with external co-existences and sequences." One of the latest definitions of life is that which has been suggested by Mr. G. H. Lewes: "Life is a series of definite and successive changes, both of structure and composition, which take place within an individual without destroying its identity." This is, perhaps, as good a definition as has yet been given; but no one of those we have quoted is more than approximately true, and a perfect definition of life seems to be an impossibility.