I9IO.] WORK ON NUTRITIVE PROCESSES. 155 



the old picture of the bookworm with his feet on the top of the desk, 

 the back hunched into an arm chair and the head enveloped in 

 tobacco smoke can hardly be considered as portraying the ideal con- 

 dition for creative work in the light of modern physiology and 

 psychology. 



Muscular Work. 



While mental effort is without appreciable influence on meta- 

 bolism, I now wish to call to your attention a most interesting series 

 of experiments on the influence of severe muscular work, particu- 

 larly such as bicycle riding, upon the transformations of the body. 

 The narrow confines of our respiration chamber make it necessary 

 for us to restrict our experiments to those forms of muscular 

 activity that do not require a large amount of apparatus or large 

 space. A form of stationary bicycle called a bicycle ergometer 

 is ideal for such experiments. We placed inside the respiration 

 chamber a stationary bicycle, the rear wheel of which was replaced 

 by a large copper disk rotating in a magnetic field. With this 

 apparatus it was possible to put an electric brake, so to speak, on 

 the copper disk and make it more or less difficult to drive the pedals 

 Without going into details, I will simply say that it is possible to 

 calibrate this apparatus and to know that every revolution of the 

 pedals with varying strengths of the electric brake results in the 

 transformation of a definite amount of energy into heat, conse- 

 quently when a man rides, we have only to count the number of 

 revolutions of the pedals to know how much heat has been trans- 

 ferred from the muscles of his body to the pedals in the form of 

 effective work. This apparatus, together with the respiration cham- 

 ber, has given us a means of studying man as a machine in a way 

 that I think has never been done before. 



One of the important problems of interest to the engineer is the 

 efficiency of his engine. How much energy of the coal can a power 

 plant convert into effective mechanical work? Obviously, the best 

 power plant is that which produces the best mechanical work out 

 of one ton of coal. With man, we also have a machine. The 

 fuel in the boiler is again the food and the muscles are the levers by 

 which the energy is transferred from the muscles to some effective 



