Nitrogen Output.
Taken in. Nitrogen in Urine. Weight of Fæces (dry).
May 18 8.668 grams. 6.06 grams. 14 grams.
19 6.474 7.17 39
20 6.691 6.33 30
------
21 8.345 6.78 83 contain 6.06% N
= 5.03 grm. N.
22 7.015 5.70
23 9.726 5.75 38
24 10.424 6.39 57
------ ------ ------
95 contain 5.76% N
= 5.47 grm. N.
------
10.50 grm. N.
57.343 44.18 + 10.50 grams nitrogen.
------ ----------------------
57.343 grams nitrogen. 54.68 grams nitrogen.
Nitrogen balance for seven days = +2.663 grams.
Nitrogen balance per day = +0.380 gram.
Average Intake.
Calories per day 2448.
Nitrogen per day 8.192 grams.
In this period of seven days the average daily intake of nitrogen was
8.192 grams, or only 0.36 gram per day more than in the first balance
period, while the average fuel value of the food amounted to 2448
calories per day. Yet the average daily output of nitrogen through the
urine for this period was 6.31 grams, or 1.2 grams per day less than
in the first balance experiment. Further, under the conditions of this
balance experiment, the body was laying up 0.380 gram of nitrogen per
day, _i. e._, showing a plus balance of 2.66 grams of nitrogen for the
seven days’ period. Again, it is to be noted that the average daily
amount of nitrogen metabolized, 6.31 grams, was 0.22 gram less than the
average daily nitrogen excretion for the entire seven months’ period,
6.53 grams. Evidently, this subject was quite able to maintain nitrogen
equilibrium with a metabolism of only 6.31 grams of nitrogen per day, on
a daily diet having a fuel value of about 2400 calories. Indeed, taking
into account the amount of the plus nitrogen balance, it is evident
that the daily food was somewhat in excess of the real requirements of
the body, under the then existing conditions of body-weight and bodily
activity.
Again, we would call attention to the thorough utilization of the food in
this experiment, emphasizing at the same time the voluminous character
of the diet, together with its largely vegetable nature. The contrast
between the diet made use of by Dr. Mendel and that used by the subject
of the first experiment is quite striking, since the latter employed
a much more concentrated diet with an average fuel value of only 1600
calories. Yet with a total intake of 57.343 grams of nitrogen for the
seven days of Dr. Mendel’s balance period, 10.5 grams only passed out
through the rectum, or 18.3 per cent, while in the second nitrogen
balance of the first subject, with the more concentrated diet, 17.1 per
cent of the total ingested nitrogen appeared in the fæces. In view of
the great divergence in the character and volume of the intake, it is
rather remarkable there should be so little difference in the relative
utilization of the two diets.
Finally, taking the average daily excretion of nitrogen through the
kidneys from November 10 to June 23, as a measure of the nitrogen
metabolized daily, viz., 6.53 grams, and taking the body-weight at 70
kilos, it is plain to see that the nitrogen metabolized per kilo of
body-weight throughout this experiment was 0.093 gram, closely similar to
the result obtained with the first subject. In other words, both of these
subjects, though widely different in body-weight, under different degrees
of physical activity, and living on different forms of diet, seemingly
required for the maintenance of equilibrium essentially the same amount
of nitrogen per kilo of body-weight; viz., with the first subject 0.0947
gram, if we take the lower figure of the last two months, and 0.093 gram
with the second subject.
Regarding the fuel value of the daily food, Dr. Mendel with a body-weight
of 70 kilos, during the second balance period, apparently utilized
on an average 34.9 calories per kilo of body-weight daily, while the
first subject, of 57 kilos body-weight, made use of only 28 calories
per kilo. The fuel value of the daily food must, however, as is well
known, vary greatly with differing degrees of physical activity, from
which arises the necessity for corresponding variation in the amounts of
non-nitrogenous foods ingested.
* * * * *
Dr. Frank P. Underhill, instructor in physiological chemistry in the
Sheffield Scientific School, is another subject of experiment who
volunteered to study on himself the effects of a lowered proteid intake.
Prior to the experiment he was in the habit of eliminating from 16 to
16.5 grams of nitrogen per day through the kidneys, representing the
usual 105 grams of proteid food metabolized.
Dr. Underhill, at the beginning of the experiment, July 1, 1903, was
twenty-six years of age and weighed 67.6 kilos. For a period of two
weeks, from July 14 to August 2, he gradually reduced the intake of
proteid food as well as the total amount of food consumed, doing this
in part by diminishing the quantity eaten at breakfast, and in smaller
measure at the two other meals of the day. During this period of two
weeks, the urine and fæces were analyzed with the results shown in the
accompanying table. Regarding the extent of proteid metabolism, it will
be seen that the nitrogen content of the urine fell from 14.28 grams per
day down to 5 to 6 grams per day. Having reached this level, the subject
maintained it throughout the summer of 1903, occasional analyses being
made to demonstrate the level of nitrogen excretion.
+-------+-------+-----------------------+-----------------------+-------+
| | Body- | Urine. | Fæces. | Total |
| Date. |weight.+-------+-----+---------+------+------+---------+ Nitro-|
| | |Volume.| Sp. |Nitrogen.|Moist.| Dry. |Nitrogen.| gen. |
| | | | Gr. | | | | | |
+-------+-------+-------+-----+---------+------+------+---------+-------+
| 1903. | | c.c. | | grams. |grams.|grams.| grams. | grams.|
|July 14| 67.6 | 1300 | 1018| 14.28 | 156.0| 30.5 | 1.59 | 15.8 |
| 15| 67.6 | 1095 | 1020| 11.72 | 70.0| 17.0 | 0.80 | 12.52 |
| 16| 67.1 | 860 | 1021| 11.72 | 182.5| 44.5 | 2.12 | 13.84 |
| 17| 66.9 | 675 | 1022| 9.39 | 134.0| 43.0 | 2.05 | 11.44 |
| 18| 66.3 | 865 | 1021| 10.45 | 57.5| 20.0 | 0.95 | 11.40 |
| 19| 65.7 | 785 | 1021| 10.34 | 170.0| 41.0 | 1.95 | 12.29 |
| 20| 65.7 | 740 | 1024| 10.34 | 76.0| 35.0 | 1.66 | 12.00 |
| 21| 65.7 | 910 | 1017| 11.61 | 96.0| 32.0 | 1.52 | 13.13 |
| 22| 65.7 | 900 | 1013| 9.50 | 56.0| 31.0 | 1.75 | 11.25 |
| 23| 65.3 | 600 | 1017| 8.65 | 41.0| 14.0 | 0.79 | 9.35 |
| 24| 65.0 | 640 | 1013| 6.65 | 151.0| 33.0 | 1.86 | 8.51 |
| 25| 65.3 | 690 | 1012| 6.01 | 86.0| 29.0 | 1.63 | 7.64 |
| 26| 65.3 | 410 | 1023| 6.65 | 57.0| 19.0 | 1.06 | 7.71 |
| 27| 65.7 | 530 | 1017| 6.75 | 202.0| 33.0 | 1.86 | 8.61 |
| 28| 65.7 | 610 | 1013| 5.49 | 155.0| 26.0 | 1.46 | 6.95 |
| 29| 66.4 | 620 | 1017| 5.96 | 121.0| 26.0 | 1.46 | 7.42 |
| 30| 66.3 | 700 | 1016| 5.80 | 233.0| 48.0 | 2.71 | 8.51 |
| 31| 65.8 | 1265 | 1010| 6.70 | 211.0| 36.0 | 2.03 | 8.73 |
| Aug. 1| 65.3 | 1240 | 1009| 6.23 | 172.0| 23.0 | 1.29 | 7.52 |
| 2| 65.3 | 760 | 1016| 6.75 | 214.0| 27.0 | 1.42 | 8.17 |
| 11| 65.3 | 500 | 1017| 6.44 | 152.0| 22.0 | 1.34 | 7.78 |
| 12| 65.3 | 405 | 1024| 6.86 | 70.0| 15.0 | 0.91 | 7.77 |
| 13| 65.3 | 540 | 1019| 6.23 | 90.0| 10.0 | 0.61 | 6.84 |
+-------+-------+-------+-----+---------+------+------+---------+-------+
In connection with the accompanying table of results, attention is called
to the composition of the fæces with special reference to their content
of nitrogen. The point to be emphasized is the gradual increase in the
percentage content of fæcal nitrogen, associated with the changed diet
and the general diminution of food intake. This is well illustrated by
the following figures, giving the percentage of nitrogen in the dry fæces
for the three periods of July 14-21, July 22-30, and August 11-13:
July 14-21, 4.77 per cent Nitrogen
July 22-30, 5.65 ” ” ”
Aug. 11-13, 6.11 ” ” ”
The diminished amount of fæcal discharge means naturally not only a
smaller intake of food, but implies also a greater utilization of the
food ingested, and as a result the increased percentage of nitrogen
in the discharges shows itself because of the relatively larger
preponderance of nitrogenous secretions from the intestinal tract.
The latter part of September, 1903, Dr. Underhill attempted to return to
his original methods of living, but found difficulty in consuming the
daily quantities of food he had formerly been in the habit of taking.
From October 11 to October 25, 1903, however, he raised the consumption
of proteid food to such a degree that the nitrogen excretion through the
urine averaged from 10 to 12 grams per day. After this date he fell back
to the lower proteid intake, and from that period to June 23, 1904, he
maintained a low level of proteid metabolism without detriment to his
bodily vigor, and, as he believes, with a distinct betterment.
The following tables of results extending from October 11, 1903, to June
23, 1904, show the data collected.