64 BULLETIN OF THE 



laws in this domain is conceded, I suppose, by the extremest of the 

 vitalists of the present day. 



We see, therefore, that, with regard to a large part of the 

 phenomena of living beings, there are grounds for affirming either 

 that they have already been satisfactorily explained by a reference 

 to established chemical and physical laws, or at least that they 

 are of such a character that it is reasonable to hope they may be 

 thus explained at some future time. Is it possible, then, to return, 

 as some have done of late years, to the old speculation of Des Cartes, 

 and look upon living beings as mere machines ? To do so, it will 

 not suffice to image to yourselves ordinary machines in which fuel 

 yields force. To satisfy the chemico-physical hypothesis of life you 

 must suppose machines that build themselves, repair themselves, 

 and direct, from time to time, new applications of their energy in 

 accordance with changes in the environment ; nay, more — machines 

 that accouple themselves together, breeding little machines of the 

 same kind that grow by and by to resemble their parents, and 

 all this self-directed, without any engineer. But even Des Cartes 

 required an engineer — the soul — to run his man-machine, and the 

 logic which compelled him to this view applies just as forcibly to 

 all the modern machine conceptions of living beings* 



I have already asserted that there are whole groups of phenomena 

 characteristic of living beings, and peculiar to them, which cannot 

 be intelligently explained as the mere resultants of the operation of 

 the chemical and physical forces of the universe. These phenomena 

 I refer — I avow it without hesitation — to the operations of a vital 

 principle, in the existence of which I believe as firmly as I believe 

 in the existence of force, although I do not know its nature any 

 more than I know the nature of force. If, for convenience, at any 

 time, I compare the living body to a machine, I must compare the 

 vital principle to the engineer — it is the director, the manager if 

 you will, but it does not supply the force that does any part of the 

 work. Let us consider, then, in the remainder of this discourse, 

 the phenomena which indicate the guidance of the vital principle. 



The first group of phenomena belonging to this second class are 

 those forced upon our attention whenever we attempt to study the 

 question of the origin of life. It has seemed to some of our contempo- 

 raries that, in accordance with the doctrine of evolution, as deduced 

 by Mr. Herbert Spencer from the great truth of the persistence of 

 force, life ought always to arise spontaneously out of inorganic 



