THE SPECIFIC CHARACTERISTICS OF 



VITALITY 



By Prof. DAVID FRASER HARRIS, M.D., D.Sc, F.R.S.E. 

 Professor of Physiology and Histology in Dalhousie University, Halifax, N.S. 



The attempts to identify life with " mechanism " depend 

 chiefly on certain analogies between living beings and man- 

 made machines or engines of some sort. 



In a certain sense living beings are mechanisms, as when 

 we choose to regard the body as a means of transmuting the 

 chemical energy of food into the kinetic forms of heat and 

 movement : here we may speak of the body as a heat engine. 

 But to insist on describing a warm-blooded animal as a heat- 

 engine is to concentrate our attention on one phase of its 

 activity and totally to overlook a number of aspects in 

 which it does not at all resemble a man-made machine. 



Certain tissues of the living body are so disposed that they 

 perform the functions of valves, levers, pulleys, hinges, all of 

 which contrivances act precisely as metal valves, levers, pulleys, 

 or hinges ; but to admit this is not by any means to see no 

 essential difference, physico-chemically, between protoplasm 

 and machines of purely human construction. To say that 

 there is no essential difference between the growth of a crystal 

 and of an infant is to magnify the resemblances out of all 

 proportion to the differences. But this sort of thing is what 

 Prof. Ostwald does when he writes, 1 " Our observations so far 

 have shown the organisms to be extremely specialised indi- 

 vidual instances of physico-chemical machines." 



He has been comparing a living organism to a flow of water 

 through a pipe ; and, by laying great stress on the truth that 

 each is not a stable but a stationary form of matter, that is, 

 the form although not the matter of the jet and of the body 

 srepectively is conserved from moment to moment, Prof. 

 Ostwald finally loses sight of any fundamental differences 

 between the non-living and the living forms. 



1 Ostwald, Natural Philosophy. London: Williams & Norgate, 191 1. 



546 



