270 Transactions of the Canadian Institute. [vol. ix 



method was the one that Pettenkofer and Voit employed in their classical 

 experiments and which is at this day perfected in the apparatus of Bene- 

 dict, for which the Carnegie nutrition laboratoriss at Boston have been 

 built. The third, as developed in the apparatus of Zuntz, has been used 

 by him and others for the study of the same phenomena in man under the 

 most diverse conditions, on balloon voyages or climbing expeditions in 

 the Alps, and in the wards of hospitals for the sick. And the outstanding 

 result of all this has been to establish abundantly and completely the 

 fundamental fact which Lavoisier's intuition led him to search after, 

 though he could not formulate it, that the sum total of the material 

 changes in living organisms is in as good accord with the laws of conser- 

 vation of energy and matter as any group of phenomena with which life 

 has nothing to do. A living organism takes in food as a furnace takes in 

 fuel; the energy of chemical structure contained in this food is trans- 

 formed into heat and work within the organism and can be shown quan- 

 titatively to be the source of all the activities which the organism exhibits, 

 no less than the fuel is the source of the heat that generates power in 

 the boilers for the working of an engine. The balance sheet of the living 

 organism can be made out in the same terms as that of the engine, and 

 the chemical changes underlying the transformation of energy are in their 

 broad outlines the same: oxidation in both gives rise to the same end 

 products — water, carbonic acid and sulphuric acid. 



The physiology that has followed this trail on which Lavoisier was 

 the first great pioneer, and that is still actively engaged upon it, has 

 established this great principle which lies at the root of all the chemical 

 interpretations of vital phenomena. But this principle established, 

 it has seemed to many that the further working out of details is not likely 

 to answer the questions that urge themselves upon the notice of all 

 questioning men. The elaboration of balance sheets based on the ana- 

 lysis of all that enters and of all that is given off from a living organism 

 becomes a tour de force and, interesting as it may be as such, especially 

 to those who have the joy of overcoming technical difficulties, it is sterile 

 and tantalizing to the hungry enquirer who wishes to see into the meaning 

 of the actual manifestations of living activity, the movements, the cor- 

 relation of working parts and the processes by which a living thing is 

 distinguished from inert matter. Those who have pursued this trail 

 have distinguished between the different kinds of material in which the 

 phenomena of life are made manifest, in many cases only because the 

 proteins give rise in the body of animals to substances that cannot be 

 exhaled from the lungs and must leave the body in solution, carrying 

 v/ith them some of the energy that was originally contained in the pro- 

 tein molecules: and for such minds the one noteworthy difference 



