210 



Capt. M. Greenwood. 



Table XII. — Heat Production and Work. Observations of Benedict and 

 Cathcart on M. A. M. pedalling at the rate of 108-112 revolutions per 

 minute (inclusive). 



Work done. 



Observed heat production. 



Mean of 

 observations. 



Heat production given by 

 formula 

 Heat =3-3271 Work + 5-1980. 



calories. 



0- 54-0 -55 



1-37 



1- 58-1-68 



2- 18-2-24 



calories. 

 6 -46, 6 -70 

 9-10 



11 -29, 11 -35, 12 -85 

 r 11 -77, 13 -02, 11 -97, 12 -72, 12 -16 "1 

 I 13-08, 11-59, 12-47, 12-17 J 



6 -58 

 9-10 



11 -83 



12 -33 



7-02 

 9-76 

 10-64 



12 -55 



I conclude, then, that the data of Benedict and Cathcart, much the most 

 extensive at our disposal, are consistent with the hypothesis that heat pro- 

 duction is, at least to a first approximation, expressible as a linear function 

 of work, H = aW -\-b, a being constant for all observed ranges of work. 



A matter which calls for discussion is the economy of thermogenesis in 

 work, a question first, I think, raised by Lefevre in 1902, and again by 

 Lapicque in 1906.* The discussion of these writers is, although not affected 

 in principle, complicated in detail by their adoption of the glueositic theory 

 of muscular energy, and I shall follow a somewhat different line of thought. 

 The fundamental notion is, of course, quite simple. A certain intensity of 

 pure thermogenesis is necessary for the bioplasm to act as an energy 

 transformer at all ; the lower limit of this is given by the heat output at 

 rest. But when the bioplasm performs work, there is, unless the conversion 

 of potential energy into work is complete, an associated liberation of energy 

 as heat and not otherwise available. Hence there is a possibility that some 

 part of the heat production necessary for the existence of the bioplasm might 

 be obtained, so to speak, as a by-product of muscular work. Carrying the 

 point to an extreme, we might have, for a certain range of work performance, 

 the range varying inversely as the real efficiency, merely to introduce equal 

 increments of heat for each increment of work, so that within that range 

 the apparent incremental efficiency, i.e., the indicated efficiency, would be 

 unity, whatever the value of the real efficiency. Of course, in this extreme 

 form, the hypothesis could not possibly be true, for it would involve a 

 complete constancy of heat production (after subtracting from the total heat 

 production the thermal equivalent of the work performed), which, since in 

 work performance the opportunity for heat loss must usually increase, could 

 not happen. But the original idea might, nevertheless, be correct. 

 * Lefevre, op. cit., pp. 910, etc. 



