NEW CONCEPTIONS IN SCIENCE 



follow more or less definitely the path of every 

 exterior sensation, whether it be one of sight or 

 sound or touch. They can trace even the course 

 of the twinge of pain that comes, say, when an un- 

 protected ringer meets with a careless thorn, and 

 they can follow more or less the resulting stimulus 

 that makes you cry out Oh! or something else. 

 And the experimental psychologist of the day will 

 time this and every other mental process to the 

 fraction of a second. 



Nevertheless, we are as yet only just beginning 

 to see the whole of the picture ; it may take another 

 quarter or half century before we shall "see it 

 clearly and see it whole," as the late Matthew 

 Arnold was wont to say. Meanwhile it is curious 

 to note that the daring guess of Moleschott, of a 

 half-century ago, might still serve fairly well to 

 describe what we know of the chemistry of the 

 brain : 



"Ohne Phosphor, kein Gedanke." 



This is not the way a physiologist of to-day 

 would phrase it exactly. The patient investigator is 

 shy of a pat phrase, that, after all, tells little. Still, 

 it is a matter of some interest to know that there 

 is a substance, as chemically definable, let us say, 

 as cheese or anthracite coal, which does our think- 

 ing. The physical basis of thought and sensation 

 is the brain and the nerves. And the vital part 



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