CHAPTER IX. 



ON THE NATUEE OF LIFE. 



WE must now turn again to Fletcher, to see the proto- 

 plasmic theory of life in its purest form, for Beale, un- 

 fortunately, has obscured the question by the revival 

 of the vital principle as the efficient cause of the pe- 

 culiar attributes of the protoplasm. I think, however, 

 it can be shown that only a very narrow line divides 

 the opinion of the two authors, and that in fact, prac- 

 tically, the theories of both are identical, as the sup- 

 posed vital principle explains nothing, and is therefore 

 superfluous. At the same time, I think it is hardly 

 worth while taking into account the views of other 

 persons than these two authors on this question, be- 

 cause unless the generic unity of the protoplasm be 

 admitted the whole theory is untenable, and as yet 

 none but those two have adopted it in its full extent. 

 Fletcher, we remember, holds vitality to be synonymous 

 with irritability, or the faculty of undergoing upon 

 the application of a stimulus, any change not strictly 

 chemical or mechanical. This property resides in a 

 substance called by him "irritable," or "living" 

 matter, which undergoes corresponding changes with 

 every manifestation of "life" or '''irritation," for "the 



