O TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



to state exactly the payment then being made in terms of 

 energy. Such a statement takes the form that at the time so 

 many calories are being liberated per unit of time, usually, 

 therefore, so many " calories per second." 



Several methods have been devised to collect the under- 

 lying necessary data during the performance of movement 

 and work ; none more convenient than that of Haldane and 

 his collaborators, which has the genius to be almost ridiculously 

 simple, and which has been shown to be sufficient. The subject 

 inflates a gas-bag with his expired air, without encountering 

 any but the most negligible resistance when doing so. He 

 carries the gas-bag on his back, and can commence and desist 

 from inflating this bag when he likes, and through a known 

 time, as measured by a stop-watch. This air is then analysed 

 in conveniently simplified apparatus designed exactly for the 

 purpose, and the account of expense at once rendered. 



Now, this simple means of rendering the account is entitled 

 to full confidence, because of the experimental labours of those 

 who have used far more elaborate and intrinsically more 

 complete methods. I can show you diagrams and introduce 

 the method of the " respiration- calorimeter " of Atwater, and 

 later of Atwater and Benedict, by which it is possible to obtain 

 separate statements of the data of respiration on the one hand, 

 and of the data of " heat-production " or of liberation of 

 energy on the other. However, it will be as well not to occupy 

 too much of your attention with the details of such complicated 

 apparatus. On these more complicated efforts, such as those 

 of the American scientists mentioned and also of German and 

 Swedish scientists, rests the foundation from which simplified 

 effort is possible. In my own experiments this more simplified 

 effort took the form of dealing only with the tale of liberated 

 energy, using the calorimetric side of Atwater and Benedict's 

 respiration calorimeter. As compared with the collection of 

 " respiration data " this alternative method offers the advan- 

 tage of greater self-sufficiency, but it is far the more elaborate, 



