CHEMICAL CHARACTERS OF CELL 83 



though all its constituents may have been Alter et 

 changed. Just as our bodies remain our bodies, ( 

 though the constituents of which they are com- 

 posed are constantly altering. One is reminded 

 of the knife which was the same knife though 

 it had had a new handle and a new blade or 

 of the more poetical simile of Wordsworth : 



For, backward, Duddon ! as I cast my eyes, 

 I see what was, and is, and will abide; 

 Still glides the Stream and shall for ever glide; 

 The Form remains, the Function never dies. 



Chemistry then does not raise the veil which 

 hides the secret of life, and physics is equally 

 incompetent to do so, indeed Lord Kelvin * 

 says that " the only contribution of dynamics 

 to theoretical biology is absolute negation of 

 automatic commencement or automatic main- 

 tenance of life." 



Movement, which we have seen to be one of Movement 

 the characteristics of living things, is not, 

 except in the form of the so-called Brownian 

 movementjt exhibited by not-living matter. 

 A stone on the moor will not shift its position 



* Properties of Matter, p. 415. 



t Robert Brown, the botanist, first rescribed these move- 

 ments in 1827, though he of course did not know that this 

 curious and continual dance of fine particles (for example, 

 of gamboge) was due to the perpetual motion of the mole- 

 cules. It is not possible in this book to deal with the 

 very abstruse problems of intra-atomic and molecular move- 

 ment (see footnote on p. 66). The movements dealt with 

 in the text are movements of transport; self-initiated and 

 carried out. 



