Bodily Labour upon the Discharge of Nitrogen. 449 



carefully into consideration all these conditions which directly or 

 indirectly affect not only the quantity, but the quality of the urine. 



Internal Conditions. — These are very various, and hardly admit of 

 accurate scientific description. There is, however, a phrase the 

 meaning of which is well known to athletes, viz., " to feel fit," which 

 will serve to illustrate my meaning. I have observed repeatedly that 

 when I have undergone any considerable physical exertion for which 

 at the outset I did not feel this " fitness," or, to use another phrase, 

 when I was "out of condition," there was- invariably a much greater 

 loss of weight than when I was " in good condition." 



No doubt atmospheric conditions have a very powerful influence 

 for or against this "fitness" for exertion, but independently of these 

 are mental and nervous states probably exceedingly complicated in 

 their origin, but none the less powerful in the influence they have 

 upon the metabolic phenomena of the body. 



The body -weight in these experiments was always taken after 

 emptying the bladder, so that the difference between the evening 

 weight and the weight next morning expresses the total loss- by skin 

 and kidneys. I attempted to eliminate the error caused by the con- 

 tents of the rectum, but very soon found that it was impossible to 

 regulate and control the bowels with the same precision with which 

 the urine can be regulated ; so that if we wish very accurately to 

 determine the significance of these differences of body- weight, we 

 must take careful note of the times at which the faeces were passed, 

 but for reasons which will be stated- under the head of the faeces the 

 difficulty is only then very partially overcome. Enough has I think 

 been said to show how exceedingly difficult it may be to determine 

 with even moderate accuracy the nature of the loss or gain in body- 

 weight, and how careful we should be in accepting arguments founded 

 on small variations. 



Daily Occupation, Meals, Sfc. — The day generally began about 9 a.m. ; 

 the variations from this time will be found in the tables of tempe- 

 rature. Breakfast followed as soon as I could prepare it. I had no 

 mid- day meal, but was accustomed to take a portion of the bread to 

 the laboratory at University College, in which most of my time was 

 spent. I dined at or about 6 p.m., and spent the evening in reading, 

 weighing and preparing food, &c. The necessities of my work some- 

 times kept me up very late. This was unavoidable, as I was not 

 able to devote my whole time to these experiments. At first I used 

 to bake my bread every evening for the following day ; but in the 

 later experiments I gave up every alternate evening to this work, as 

 I found I saved time by the arrangement. Supper was taken at 

 various times after 11 p.m. 



Arrangements on Days of Exercise. — Under ordinary circumstances, 

 that is to say, when the walk could be easily accomplished between 



