142 HUXLEY 



Thirteen years earlier he had said the same thing 

 on a Sunday evening in November to an Edinburgh 

 audience. Like his wonderful discourse on " Animal 

 Automatism," delivered before the British Association 

 at Belfast, his Edinburgh " lay sermon " on " The 

 Physical Basis of Life" was spoken without depend- 

 ence on note or reference, and afterwards written out 

 from memory for publication. Following on the 

 demonstration of the identical constitution of proto- 

 plasm as the raw stuff which builds up the cell as the 

 structural foundation of every living thing, Huxley 

 showed that the protoplasm itself is built up of cer- 

 tain compounds, and that "a threefold unity — namely, 

 a unity of power or faculty, a unity of form, and a 

 unity of substantial composition — pervades the whole 

 living world." 



In whatever form protoplasm is manifest, whether, 

 as in the very lowest plant or animal, without a 

 nucleus, or, as in the higher organisms, nucleated, 

 there are found four of the elementary substances, 

 carbon, hydrogen, oxygen, and nitrogen, in very com- 

 plex union. These non-living materials the plant, 

 and the plant alone, by some mysterious alchemy, 

 converts into a living thing, and upon this the animal 

 sustains life. It is not easy to determine where the 

 plant ends and where the animal begins, since some 

 organisms exhibit the characters of both, but, broadly 



