328 



THE ROTHAMSTED EXPERIMENTS. 



Nitrogen 

 not ac- 

 counted 

 for. 



Experi- 

 ments at 

 Rotham- 

 sted; how 

 conducted. 



Food used. 

 Nitrogen 

 consumed 

 and voided. 



Nitrogen 

 not ac- 

 counted 

 for. 



the same ration for three months, and did not either gain or 

 lose in weight appreciably. There was here again an amount 

 unaccounted for, representing a loss of 17.2 per cent of the 

 nitrogen of the food. 



In the two experiments with turtle-doves, one over five 

 and the other over seven days, each of the birds rather 

 lost weight. Their food was millet ; and in the one case 

 there was a loss of 35.9, and in the other of 34.1, per cent 

 of the nitrogen in the food. Boussingault thought that there 

 was undoubtedly a loss of nitrogen, as the amount unre- 

 covered was far too great to be accounted for by errors of 

 analysis. 



Experiments were made on the subject at Eothamsted in 

 1854 with pigs. Individual male animals were experimented 

 upon, for periods of three and of ten days. Each animal was 

 kept in a frame, preventing it from turning round, and having 

 a zinc bottom sloping slightly from each side towards the 

 centre, where there was an outlet for the urine to run into a 

 bottle beneath. They were watched night and day, and the 

 voidings carefully collected as soon as passed, which could 

 easily be done, as the animals never passed either faeces or 

 urine without getting up, and in so doing rang a bell, and thus 

 attracted the notice of the attendant. The constituents 

 determined were — in the food and fasces, dry matter, ash, and 

 nitrogen ; and in the urine, dry matter, ash, nitrogen, and 

 urea. In preparing samples of faeces or of urine for nitrogen 

 determinations, a mixture was made of a proportional part of 

 the voiding of each twenty-four hours, and oxalic acid added. 

 In the case of the fasces, portions of the acid mixture were 

 taken for the determination of dry matter; and nitrogen 

 determinations were made in the partially dried substance, 

 and calculated up to the fully dried condition. In the case of 

 the urine, portions of the acid mixture were fully dried, and 

 other portions partially dried, and then mixed with about 

 half the weight of fully dried oak-dust, in which the nitrogen 

 was determined. 



Over a preliminary period, and also over each period of 

 exact experiment, one animal received the highly nitrogen- 

 ous lentil-meal, and the other the low - in - nitrogen barley- 

 meal. In each case, the one receiving lentil-meal consumed 

 more than twice as much nitrogen in food, and voided more 

 than twice as much in the solid and liquid excrements. 



Notwithstanding the great attention paid to the collection, 

 the sampling, and the preparation of the samples of the excre- 

 ments for nitrogen determinations, as above described, there 

 was, in each case, a considerable amount of the nitrogen of 

 the food unaccounted for in that estimated in the increase 



