ESSAY-REVIEWS 103 



venture to hope they are disposed of by the destruction of his 

 primary argument. 



I may perhaps be allowed briefly to allude to one. In the 

 case of warm-blooded animals, there occurs an obvious wastage 

 of heat by radiation into the environment ; this would appear at 

 first glance as an illustration of the second law of thermody- 

 namics ; but Dr. Johnstone is compelled by his theory to deny 

 this apparently obvious application. He affirms accordingly 

 that the production of heat is not a mere chance by-product of 

 organic metabolism, but is a " purposeful " activity of the 

 organism. With this view we may quite well agree ; but we 

 cannot agree that because the evolution of heat has a teleological 

 value, it is, therefore, any the less a manifestation of thermody- 

 namic principles. Nearly all the bodily functions are " pur- 

 posive"; but for all that they are produced by "blind" 

 physico-chemical means. In steam-engines, there occurs a 

 wastage of heat from the boiler, by the loss of hot furnace- 

 gases up the chimney and in other ways. This wastage is 

 that contemplated in the second law of thermodynamics. But 

 it may be, and constantly is, greatly minimised by fitting in the 

 flue an " economiser," or nest of tubes exposed to the hot gases 

 and containing the water to be fed to the boiler. By increasing 

 the size of the economiser, it is possible to extract as much 

 heat as is desired from the wastage and add it to the boiler 

 water. In this case we may affirm that the heat in the waste 

 gases has a purposeful signification, for it markedly raises the 

 efficiency of the engine. The case is analogous to that of heat- 

 production in animals. The exhaust-steam turbine provides 

 another analogy. This turbine, especially used for the winding 

 engines of collieries, is driven by steam (taken at atmospheric 

 pressure or a few pounds above it) that is exhausted from ordi- 

 nary non-condensing engines. The heat dissipated under the 

 second law of thermodynamics from one engine is thus used 

 to drive another. But the fact that it is put to a definite purpose 

 does not in any way invalidate the fact of its original production 

 as a frictional by-product. 



It is interesting historically to note that, whereas the older 

 vitalists attempted to show that organisms were outside the 

 control of the first law of thermodynamics, the newer now 

 apparently have shifted their attention to the second law. It 

 has at length been proved abundantly that organisms fall within 



