Experiments on the metabolism of matter and energy in the human body / By W.O. Atwater, PH.D., and F.G. Benedict, PH.D., with the cooperation of A.W. Smith, M.S., and A.P. Bryant, M.S.

  • Atwater, W. O. (Wilbur Olin), 1844-1907.
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Experiments on the metabolism of matter and energy in the human body / By W.O. Atwater, PH.D., and F.G. Benedict, PH.D., with the cooperation of A.W. Smith, M.S., and A.P. Bryant, M.S. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    this division into periods is to obtain information, if practicable, regard- ing the nitrogen lag, i. e., the interval of time during which the excre- tion of nitrogen l;»gs behind the nielabolisni in the body. We have found comparatively few data for determining the exact duiation of this lag. It is not known, for instance, at what time the nitrogen of the food eaten for bi eakfast begins to appear in the urine, nor when the nitrogen of the food eaten for supper of any given day is all metabolized and excreted. Still less do we know how long a period intervenes between the metabolism of nitrogen of tissue and its excretion. It is believed by some experimenters that, under ordinary conditions, the actual nitrogen consumed in the food is soon excreted. In previous experiments' of this series a lag of six hours is assumed in one case and twelve hours in another. One advantage in making the diet uni- form for the four days pre(;eding the metabolism experiments, as has been done in the cases here reported, is that during this time the sub- ject will reach approximate nitrogen equilibrium and that for the pur- pose of the experiment the nitrogen day, i. e., the twenty-four hours during which the nitrogen is excreted may be taken as coincident with the exjjerimental day, thus allowing for no lag. This i)robably gives results as nearly coriect as would be obtained by any such arbitrary assumption. The data are, however, given in the tables by which the calculations can be revised to allow for a nitrogen lag of six, twelve, or, in some cases, tweuty-ftmr hours' duration. For this i)urpose the nitro- gen in the urine is determined for periods of from six to twenty-four hours after the end of each experiment. PERSPIRATION PRODUCTS—ELIMINATION OF NITROGEN. The amount of matter eliminated in the i)erspiration is not large. During several of the rest experiments it was found that the nitrogen thus eliminated amounted to less than 25 milligrams per day. In work experiments, on the other hand, as much as 0.2 gram of nitrogen was eliminated by the skin in a day. The nitrogen of perspirsition was determined as follows: The subject took an ordinary bath and afterward rinsed his body with distilled water before entering the chamber. His underclothing, which was of medium weight, was carelully rinsed witii distilled water after the usual washing. He had a clean suit of underclothes every night to replace the suit worn during the day. The latter suit was washed with dis- tilled water, which was then evaporated nearly to dryness and the nitrogen in the residue was determined by the Kjeldahl method. The nitrogen of the products of persjuration was thus determined in rest experiments Nos. 5 and 7, and in all the work experiments. RESPIRATION PRODUCTS- OARIJON AND HYDROGEN. In all the experiments the only res))iratory ])ioducts determined were carbon dioxid and water. I'Vom these the carbon and hydrogen were