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stated. 58 Eugene Gley, in a recently published essay, claims to 

 have obtained similar results, and states that at the same time the 

 sphygmographic trace of the carotid artery shows a higher upstroke 

 of the recording lever, aud other indications of dilatation of the 

 vessel. 59 While these observations are not sufficiently numerous, or 

 free from objections, to be accepted without question as proof that 

 an increased supply of blood to the brain invariably accompanies 

 mental effort, they are certainly sufficient to encourage further labor 

 in this interesting field. 



But if the arguments in favor of the purely material nature of 

 our mental operations that have been based upon the imperfect re- 

 sults of the three lines of investigation I have just referred to must 

 be rejected as utterly fallacious, what shall we say of the logic that 

 attempts to draw a similar conclusion from the results of those 

 inquiries into the phenomena of personal equation which aim at 

 determining the time that must be allowed for the mental operation 

 involved? 60 Do we, then, indeed need the beautiful experiments 

 of Hirsch and Donders 61 to prove that thought occupies time? 

 Whence, indeed, do we derive our primitive conceptions of time 

 save from our consciousness of the succession of thought ? And 

 how could even the shortest time be occupied by even an infinite 

 number of thoughts if each thought did not occupy at least some 

 time, however brief? 



I have thus, gentlemen, attempted to show that we are logically 

 compelled to iuvoke the existence of a vital principle in order to 

 account for certain important groups of phenomena occurring in 

 living beings which cannot possibly be explained by the chemical 

 and physical forces of the universe. These phenomena form a 

 series, at one end of which we find the mere irritability or sensi- 

 bility of the humblest mass of living protoplasm ; at the other the 

 reasoning faculty of the human mind. From the one extreme of 

 this series to the other I recognize the manifestations of the vital 

 principle. I willingly confess that I know nothing of the ultimate 

 nature of this principle, except that it must be very different from 

 the chemical and physical forces whose operations I have learned 

 to recognize in the organic as well as in the inorganic world ; never- 

 theless I am compelled by my study of the phenomena to conclude 

 that it exists. I know that Mr. Huxley, only last summer, declared 

 in the International Medical Congress at London, that the doctrine 

 of a vital principle is the "asylum ignorantise of physiologists;" 62 



