LIFE AND ORGANISATION. 59 



We may dwell somewhat further still on this argument of 

 the relation of the great physical forces to vital phenomena, 

 inasmuch as the question is really supreme among those which 

 relate to the theory of life. It is obvious as a principle in 

 conducting it, that we must proceed upwards from the lowest 

 and simplest forms which occur in the scale of being. If 

 in these the properties of life and reproduction depend 

 on physical agents alone, without any new and unknown 

 principle of power being added, we must needs carry the 

 conclusion onwards to higher grades of organisation. No 

 line of limitation exists, obvious either to the senses or to 

 reason. Some might conjecture it to lie in the distinction 

 between animal and vegetable life. But, even acquiescing in 

 all that is expressed in this distinction, can we fairly claim 

 for the Medusae or the Oyster a peculiar cause or principle of 

 life, which we deny to the Sensitive plant, the Dionaea Mus- 

 cipula ; or to the common Nettle, Berberry, and various other 

 plants, each endowed with some peculiar sensibility or motive 

 power ? That the same natural forces have influence on all 

 these organisms is certain. Are we to suppose some mys- 

 terious agent, yet unrecognised, as needed in addition to 

 explain the appropriate functions of animal life, even in their 

 simplest form of organisation ? 



This particular question is obviously subordinate to the 

 larger one we are now discussing. The grounds of argu- 

 ment are the same, the difficulties exactly alike. Thus far 

 we have dwelt more especially on chemical action, as giving 

 us closest access to the laws of vitality. But Electricity, that 

 wonderful agent on our own globe, and probably throughout 

 all space which, scarcely known a century ago, is now the 

 most powerful instrument in the hands of man bids fair 

 to become an equal exponent of the vital functions, and 

 especially of those important functions which belong to the 

 ervous system. We shall have occasion to recur to this 



