Bodily Labour upon the Discharge of Nitrogen. 



461 



various artificial means to distinguish one day from another by eatmg 

 something indigestible, and attempting to use the position of this 

 body as a line of demarcation between one day and the next, but all 

 attempts have hitherto proved futile. 



This difficulty presents itself with the greatest force at the begin- 

 ning of an experiment, because from the concentrated nature of my 

 diet, it is liable and as a matter of fact almost always at first induces 

 slight constipation. 



Now that I adopt the plan of fasting from twenty-four to thirty-six 

 hours before commencing an experiment, this difficulty is diminished ; 

 nevertheless in one or two cases I have found that having taken a large 

 quantity of milk on the day before starvation, in order that by the colour 

 of the dejecta I might have some guide to their distribution and origin, 

 that the first fseces passed after the fast, sometimes not till the second 

 day of the experiment, would contain traces of this milk, although the 

 bowels had been freely moved in the twenty-four hours after it was 

 taken. 1 fear we must admit the impossibility of completely empty- 

 ing the intestines each day, and be content with results obtained as 

 they are throughout these experiments by the method of averages. 

 Even when the bowels are moved regularly every day at the same 

 hour, the amount of dry material is by no means constant, and even 

 when it happens to be the same, the amount of nitrogen contained in 

 each day's quantity may be very different. 



Microscopic examination showed that digestion of my experimental 

 diet was very complete, the undigested matter consisting almost 

 entirely of fragments of vegetable fibre, and a few starch granules 

 (generally burst). Repeated examinations of a watery extract, pre- 

 pared by boiling the dry material, failed to show the presence of 

 either starch or sugar in any appreciable quantity. On one occasion 

 on which I suffered slightly from diarrhoea, the extract of the ash 

 contained an almost weighable amount of chlorides, and the amount 

 of sulphates rose to what might be called " strong traces/' 



The whole of the analyses of food and excreta were done at least 

 twice, and whenever a very discordant result was obtained, a third 

 analysis was always made ; the figures given in the tables are therefore 

 invariably the mean of at least two results, closely agreeing. 



Methods used in the Analysis of Foods. 



Nitrogen. — The soda-lime process was used in all cases, every care 

 being taken to ensure complete combustion, by very slow burning 

 and the use of extra long tubes. The great concordance of the results 

 is, I think, a satisfactory answer to most of the objections which can 

 be urged against the method. The following are examples : — 



