248 Mr. J. J. Woodward on the Modern 
we continually encounter the preponderating influence of 
purely physical laws. ‘The introduction of air into the lungs 
of breathing animals and its expulsion thence is effected in a 
purely mechanical way, while the exchange of the carbon 
dioxide of the blood with the oxygen of the inspired air occurs 
in strict obedience to the laws of the diffusion of gases. 
The ordinary laws of hydraulics govern the circulation of 
the blood and lymph, and all the complex visible motions of 
the body are executed in accordance with the ordinary laws 
of mechanics ; nor is it at all necessary for me to insist upon 
the purely physical nature of the operations of the organs of 
the special senses, conspicuously the eye and the ear. For 
example, so far as concerns the means by which images of 
external objects are formed sharply upon the retina, the eye 
is as purely a physical instrument as the telescope or the 
microscope. But I need not dwell upon this group of pheno- 
mena, because the importance of the réle of the ordinary 
physical 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 suftice to image to 
yourselves ordinary machines in which fuel yields force. To 
satisfy the chemico-physical hypothesis of lite you must sup- 
pose 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-con- 
ceptions 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. ‘Lhese phenomena I reter—I avow it without 
hesitation—to the operations of a vital principle, in the 
