SCIENCE AND PHILOSOPHY 151 



physics and chemistry tell us? It can tell us how 

 the energy for the journey is obtained from 

 chemical explosions of reserve material in the 

 muscles of the eel's tail. It can tell us some of 

 the steps in the making of these reserve materials 

 out of the eel's food. It can tell us that the 

 muscles are kept rhythmically contracting by 

 nervous stimuli, and so on for a whole volume, 

 and yet it does not help us to understand the 

 migration to the spawning-grounds. To take 

 items in the process and reduce them (as far as 

 possible) to physical and chemical common denom- 

 inators, does not make any clearer the inter-con- 

 nection of all these items into the single act of 

 migration. Apply physico-chemical methods by 

 all means, the results are always of interest, but 

 the results are not useful in making the biological 

 fact of migration more intelligible. 



Let us linger over the illustration, for it is 

 very instructive. As Russell says: "The migra- 

 tion is, so to speak, a fact of a higher order than 

 any physical or chemical fact, although it is made 

 up of an indefinitely large number of physical and 

 chemical facts. To explain the fact one must 

 accept it as a whole, not seek to conquer it by 

 dividing it, for if one analyses it into its com- 

 ponents one inevitably misses the bond of union. 

 . . . To decompose the act of migration into an 

 infinity of physico-chemical processes is to take 



