112 Studies in Heat-production Associated with Muscular Work. 



its appearance in these expressions because the weight of the limbs that are 

 moved is at first a large fraction of the whole sum of mechanical work which 

 is performed. Or, on the other hand, it might be considered that W enters 

 in some less direct fashion as a representative of mass rather than of 

 weight, since it is clear that the value "heat-production/mass" must to 

 some degree determine the temperature of the musculature, and further, as is 

 well known to be true, the heat-production would be expected to vary with 

 this temperature, as well as with the mechanical work which is performed. 



On either of these assumptions as to the importance of W, it is con- 

 ceivable that at first the expression for the heat-production of rest was 

 complicated in such a fashion that 



Production/ Surface became Production/(W x Surface)*; 



that is to say, that the denominator might change from W 2 / 3 to W 5 / 3 . Now 

 we have only to consider that the withdrawal of the dominating influence of 

 the surface, the removal of one kind of automatic nervous control, passes on 

 further than to mere elimination until the surface becomes now the humble 

 agent of the heat-production under the influence of a reversed nervous 

 control. This is, indeed, what actually happens, but is it not the case, this being 

 so, that now the heat-production will tend to vary inversely as the surface ? 



Heat-production becomes Heat-production x Surface 



W x Surface W 



and the denominator changes from W 5 / 3 to W 1 / 3 . 



Now, finally, we come to consider the state of affairs represented by 

 Group D, where, apparently, both weight and surface have dropped out of 

 account. Here it is open to us to consider that the surface has now become 

 a cubic quantity with the same dimensions as the weight, and that they are 

 thus both cut out from the expression for the heat-production. Nor is this 

 so absurd as might at first appear, since the process of sweating introduces a 

 further quantity, by which the extent of the surface is multiplied, and 

 might very well be regarded as a third dimension. Or else we revert to the 

 position that the weight of the limbs becomes less and less important as the 

 amount of externally useful mechanical work rises in value, and that in 

 this way there is a tendency to minimise the value of W in the denominator. 

 If this is so, then it is to be anticipated that a further continuance of these 

 experiments will lead to the further observation that, at a still higher level 

 of work-performance, the heat-production will be found equal to KW - ", and 

 the weight then have an appearance of being a positive advantage, since 

 there is then no obvious reason why the surface should disappear from the 

 numerator. 



