CHAPTER XXXVII 

 THE EFFICIENCY OF THE ORGANISM 



By E. P. CATHCART, M.D., D.Sc., F.R.S., Gardiner Professor of Chemical 

 Physiology, University of Glasgow. 



THE consideration of the efficiency (i.e. the relation of the 

 consumption of energy in the form of fuel to the output of 

 energy in the form of effective work) of man in the production 

 of external work is a question not merely of great physiological 

 but of economic importance, as this factor plays an important 

 role in the assessment of an adequate diet. Physiologically we 

 are concerned with the abstract problem of the conversion of food 

 energy into work that is, the problem is simply the relation of 

 the increased energy output during the actual performance of 

 muscle work to the energy expenditure of a similar period when 

 no work is being done. In the case of industry, armies, etc., the 

 question is plain enough, but there are many factors both psychic 

 and physical which qualify the answer, in other words, the types 

 of work, the conditions under which it is performed and the 

 personal qualifications of the performer all play an important part 

 in the degree of efficiency with which the work is carried out. 

 Hence it is very essential that the " net or physiological " efficiency 

 be differentiated from the " gross, crude, or industrial " efficiency. 

 The "net" efficiency may be defined as the value obtained by 

 dividing the heat equivalent of the external effective muscular 

 work by the increase in energy output of the body developed as 

 the result of the work done. The "gross" efficiency, on the 

 other hand, is the value obtained as the result of dividing the heat 

 equivalent of the external effective muscular work by the total 

 energy output of the individual during the period in which the 

 work was done. The following table will make the point 

 clear : 



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