Bodily Labour upon the Discharge of Nitrogen. 451 



hand, that I was careful always to dine rather earlier on the day 

 before the exercise, and to consume all my remaining bread at that 

 meal, leaving only a cup of cocoa to be taken later to complete the 

 day's allowance, and this I generally took between 8 and 9 p.m., 

 instead of at 11 p.m. as on other days ; so that I think I may safely 

 say that my food had at least the usual time for digestion and the 

 products to pass into the urine. 



It may possibly be asked, why I did not adhere to my ordinary 

 meal times and arrange for the consumption of my dinner on the 

 road ? I would reply, that the object of these experiments was to 

 determine the effect of muscular labour upon the nitrogen contained 

 in the body, and not the disposition of material supplied to the 

 organism whilst in a state of great activity. This I consider to be a 

 different problem from the one actually before us, and which will 

 require investigation by somewhat different methods from those 

 which I have adopted in these researches. True T have found it 

 necessary to eat something during the work, but this was only the 

 same as was eaten on other days on which no work was done. 



The Diet. — In all experiments of this kind, the diet is of prime 

 importance. Our ordinary food-stuffs do not lend themselves readily 

 to analysis, are very variable in their composition, and are in many 

 respects very unsuited to the purpose. 



The conditions which the diet for such researches must satisfy are 

 these : — 



(I.) It must be of such a nature as to resemble as nearly as pos- 

 sible the ordinary food of the individual experimented upon. 



(2.) It must admit of being accurately sampled for analysis. 



(3.) It must keep for such a length of time that one experiment at 

 least can be made with the same material. 



The ordinary components of a mixed diet do not satisfy the last 

 two conditions in any sense whatsoever, and the extreme difficulty of 

 determining the ingesta accurately led me, after many trials, to use 

 special methods of preparing the following articles for the purposes 

 of these researches : — 



Bread. 

 Meat. 



Green vegetables. 



Potatoes. 



Milk. 



Fat. 



Apples. 



Cocoa. 



Bread. — In order to secure perfect uniformity in the quantity and 

 quality of this article, I took a sufficiency of one sample of flour to 



