Bodily Labour upon the Discharge of Nitrogen. 



445 



to the subsequent period, and the form of the curve would be such 

 that of the two spaces included between it and the axis, the one 

 above would never exceed the one below, provided the period of obser- 

 vation were sufficiently prolonged. It has been a primary object of 

 the present inquiry to determine whether a result in this form can be 

 invariably obtained or not; its value, if obtained, would lie, not of 

 course in its affording evidence that increased expenditure of nitrogen, 

 consequent on work, is balanced by diminished expenditure afterwards 

 (for this has been already shown, and has in itself very little signifi- 

 cance), but in its proving that the increase is not and cannot be an 

 effect of increased intake, that the over-expenditure of nitrogenous 

 material which work determines is exclusively expenditure of pre- 

 viously stored material, and consequently that the degree of effect 

 produced by work will vary according to the state of the body in 

 respect of storage at the time at which the work is done. 



The subject-matter of the present paper will for the sake of clear- 

 ness be discussed under the following heads : — 



(1.) Plan of Experiment. 



(2.) Observations on Pulse, Temperature, Respiration, and Body- 

 Weight, before, during, and after work. 

 (3.) Experimental Diet. 

 (4.) Methods of Collecting Excreta. 

 (5.) Methods of Analysis of Food and Excreta. 

 (6.) Nature of the Work done. 



(7.) Detailed Statement and General Summary of the Quantitative 

 Results of Experiments. 



In the concluding paragraphs an attempt will be made to set forth 

 the inferences to which the experiments lead, and to indicate the direc- 

 tion which must be given to further inquiry. 



TJie Plan of Experiment. 



I always began an experiment with the intention that it should 

 extend over at least nine days, which I divided as follows : — Four 

 days' ordinary occupation, one day work, and a second period of four 

 days' ordinary occupation, or more if I thought it necessary for the 

 complete subsidence of any effects produced by the work. In addition 

 to this I usually prepared myself some days (ten or twelve) before, 

 by living exceedingly regularly, and always having the same kind, 

 and as nearly as possible, without weighing, the same quantity of 

 food ; further, in order to get rid of what in a former paper* I have 

 called reserve nitrogen, I have found it necessary somewhat to increase 

 my daily exercise for a few days before commencing an experiment, 

 or, as in my later investigations, to take the additional precaution of 



* "Journal of Physiology, " vol. i. 



