THE EFFICIENCY OF MAN AND THE 

 FACTORS WHICH INFLUENCE IT. 



ADDRESS TO SECTION I (pHYSIOLOGY) BY 



Professor E. P. CATHCAET, M.D., D.Sc, P.E.S., 



PRESIDENT OF THE SECTION 



The subject of my address — the efficiency of the human organism and 

 the factors which influence this efficiency — is, in my opinion, one of 

 the most important problems of the present day. It is a problem which 

 cannot, however, be considered only from its physiological aspect if it 

 is to receive adequate consideration; its imijlications are much wider, 

 reaching right down to the very basis of our daily lives. As I am no 

 expert in industry or economics, I shall confine my attention as far as 

 possible to the problem from the physiological side, and leave to others 

 the sociological application. 



The term ' efficiency ' has become a mere catchword, bandied about 

 by people who have not the faintest idea of what the word connotes. 

 Practically it has come to mean, to the average man in the street, the 

 mythical improvement which is to be anticipated from some change 

 in workshop or office organisation — a bigger and better result at a 

 smaller cost- The word has a very definite meaning in engineering 

 science, and this meaning has been transferred from the inanimate 

 machine to the living organism. In the case of the engine the problem 

 is relatively simple, as the number of interfering factors is not great, 

 but the solution of the problem in the case of the organism is beset 

 with many difficulties, as the interfering factors are numerous and 

 varied. Two types of efficiency are spoken of in connection with the 

 animal body. One type is the mechanical efficiency in the engineering 

 sense, i.e. the ratio which exists between the heat equivalent of the 

 external muscle work done and the energy output of the subject during 

 the performance of the work in question. This is a problem which 

 has attracted many workers, and there seems to be a general consensus 

 of opinion that the efficiency of man in the performance of external 

 work is about 20 per cent, gross and 25 per cent. net. (Gross efficiency 

 is obtained by dividing the actual heat equivalent of the external 

 work done by the total output of energy of the man during the time 

 occupied in the performance of the external work, and net efficiency is 

 obtained by dividing the heat equivalent of the external muscle work 

 done by the actual increase in the energy output of the subject over 

 the basal energy output during the performance of the work in 

 question.) As A. V. Hill has pointed out, this striking unanimity is in 



