From November 10, 1903, to June 23, 1904, a period of about seven months and a half, the average daily excretion of nitrogen through the urine was 6.53 grams. In other words, throughout this long period the average daily amount of proteid matter metabolized was 40.8 grams, only a little more than one-third the amount called for by the Voit standard. Until February, the body-weight gradually fell, but from the early part of February until the end of the experiment the body-weight remained practically stationary at 70 kilos. Dr. Mendel, however, from the necessities of his daily work in the laboratory was compelled to a much greater degree of physical activity than the subject of the preceding experiment, and consequently required a larger amount of non-nitrogenous food than the latter. Further, owing to his greater physical activity and the necessary variations in this daily activity, it was not so easy at first to attain equilibrium.

On February 9, a balance experiment of six days was commenced, with a careful comparison of the nitrogen intake and output. In the accompanying tables are shown all of the data. By scrutiny of these it will be seen that Dr. Mendel had adopted essentially a vegetarian diet. During this period of six days, however, he was not in nitrogen equilibrium, neither was he strictly in body equilibrium, since there was a distinct tendency for the body to fall off in weight. In this connection it may be mentioned that there is always a tendency during a balance experiment of this character for the subject to eat less than he is ordinarily accustomed to, owing to the tediousness of weighing every particle of food consumed. Further, for the same reason, and to avoid excess of chemical work in the analysis of samples of food, he is inclined to limit his diet to a few articles and thereby unconsciously restricts his intake of food, sometimes disastrously so.

Tuesday, February 9, 1904.

Breakfast.—Bread 33 grams, sugar 20 grams, coffee and milk 210 grams.

Lunch.—Consommé 150 grams, sweet potato 170 grams, bread 135 grams, tomato 106 grams, coffee and milk 210 grams, sugar 20 grams.

Dinner.—Bread 75 grams, mashed potato 200 grams, string beans 91 grams, apple pie 282 grams, coffee and milk 210 grams, sugar 20 grams, water 100 grams.

Wednesday, February 10, 1904.

Breakfast.—Bread 37 grams, sugar 20 grams, coffee and milk 210 grams.

Lunch.—Bread 110 grams, sugar 7 grams, milk 250 grams, apple fritters 90 grams.

Dinner.—Bread 37 grams, sugar 21 grams, baked beans 100 grams, cranberry sauce 125 grams, coffee and milk 210 grams, molasses candy 54 grams.

Thursday, February 11, 1904.

Breakfast.—Bread 40 grams, sugar 20 grams, coffee and milk 210 grams.

Lunch.—Bread 95 grams, sweet potato 130 grams, sugar 7 grams, milk 250 grams, peach preserve 93 grams.

Dinner.—Bread 90 grams, mashed potato 100 grams, tomato purée 135 grams, baked beans 75 grams, lemon pie 110 grams, coffee and milk 210 grams, sugar 21 grams.

Friday, February 12, 1904.

Breakfast.—Bread 58 grams, sugar 21 grams, coffee and milk 210 grams.

Lunch.—Bread 120 grams, sugar 21 grams, custard 76 grams, milk 250 grams, coffee and milk 125 grams.

Dinner.—Bread 67.5 grams, sugar 21 grams, mashed potato 150 grams, lima beans 80 grams, coffee and milk 210 grams, apple dumpling 131 grams, molasses candy 27 grams.

Saturday, February 13, 1904.

Breakfast.—Bread 47.5 grams, sugar 28 grams, coffee and milk 210 grams.

Lunch.—Bread 57 grams, sugar 40 grams, sweet potato 135 grams, quince preserve 73 grams, apple turnovers 118 grams, coffee and milk 310 grams.

Dinner.—Bread 59 grams, mashed potato 175 grams, peas 80 grams, apple pie 141.5 grams, sugar 21 grams, coffee and milk 210 grams.

Sunday, February 14, 1904.

Breakfast.—Bread 50 grams, sugar 21 grams, banana 92.5 grams, coffee and milk 210 grams.

Lunch.—Bread 108.5 grams, sugar 28 grams, baked potato 165 grams, apple sauce 114 grams, coffee and milk 210 grams.

Dinner.—Bread 63 grams, sugar 28 grams, succotash 75 grams, mashed potato 200 grams, chocolate layer cake 80 grams, ice cream 73 grams, coffee and milk 210 grams.

NITROGEN BALANCE.—Mendel.

Average Intake.

In this balance period of six days the average daily intake of nitrogen was 7.83 grams, coupled with an average fuel value of the food per day of 1975 calories. This latter value was obviously too small for a man of Dr. Mendel’s body-weight, and doing the amount of physical work he was called upon to perform. Being on one’s feet in a laboratory six to eight hours a day, in addition to the ordinary activity of a vigorous man leading a strenuous life, necessitates the utilization and oxidation of considerable food material. The average daily output of nitrogen through the urine amounted to 7.50 grams, considerably above the average daily excretion for the seven months’ period. Still, under these conditions there was a minus balance of 7.13 grams of nitrogen for the six days’ period, indicating that the body was drawing upon its stock of proteid material to the extent of 1.19 grams of nitrogen per day. This does not necessarily mean that the body had need of that additional amount of proteid matter each day, but rather that the amount of total energy required was beyond the potential energy supplied by the food. There not being sufficient non-nitrogenous food at hand, the body was compelled to draw upon its own resources, and in so doing utilized some of its tissue proteid. This is made quite clear by the results of the second balance period shortly to be described.

It is evident, however, that while the body was not in nitrogen equilibrium for this particular period of six days, there must have been a general condition of both body and nitrogen equilibrium, otherwise the body-weight would not have remained practically stationary for so long a period as from February 7 to June 20.

Commencing May 18, a second nitrogen balance was attempted, in which, as in the preceding case, there was a careful comparison of income and output for seven days. There was as before a free choice of food, but it was essentially vegetable in character. A greater variety of foods was taken, however, and an effort was made to have the non-nitrogenous food somewhat more liberal in amount, though in as close harmony as possible with the desires of the appetite.

Wednesday, May 18, 1904.

Breakfast.—Banana 92 grams, bread rolls 28 grams, cream 50 grams, coffee 150 grams, sugar 21 grams.

Lunch.—Bread 66 grams, soup 150 grams, farina 154 grams, sweet potato 123 grams, beans 70 grams, syrup 50 grams, coffee 150 grams, cream 50 grams, sugar 14 grams.

Dinner.—Bread 42 grams, consommé 100 grams, spinach 100 grams, mashed potato 250 grams, apple pie 97 grams, coffee 150 grams, cream 50 grams, sugar 21 grams.

Thursday, May 19, 1904.

Breakfast.—Banana 102 grams, bread rolls 50 grams, coffee 150 grams, cream 50 grams, sugar 21 grams.

Lunch.—Bread 57 grams, egg omelette 20 grams, hominy 137 grams, syrup 68 grams, potatoes 128 grams, coffee 100 grams, sugar 21 grams, cream 50 grams.

Dinner.—Tomato purée 200 grams, bread 24 grams, fried sweet potato 100 grams, spinach 70 grams, Indian meal 100 grams, syrup 25 grams, coffee 100 grams, sugar 21 grams, cream 40 grams.

Friday, May 20, 1904.

Breakfast.—Sliced orange 140 grams, coffee 100 grams, cream 30 grams, sugar 21 grams.

Lunch.—Bread 28 grams, mashed potato 250 grams, lima beans 40 grams, coffee 100 grams, sugar 21 grams, cream 30 grams, fried hominy 115 grams, syrup 48 grams.

Dinner.—Bread 19 grams, consommé 150 grams, string beans 140 grams, mashed potato 250 grams, rice croquette 93 grams, cranberry jam 95 grams, coffee 100 grams, sugar 21 grams, cream 30 grams, syrup 25 grams.

Saturday, May 21, 1904.

Breakfast.—Banana 153 grams, coffee 150 grams, sugar 21 grams, cream 30 grams.

Lunch.—Bread 25 grams, potato croquette 229 grams, Indian meal 109 grams, tomato 123 grams, syrup 48 grams, coffee 100 grams, sugar 14 grams, cream 20 grams.

Dinner.—Bread 31 grams, bean soup 100 grams, fried potato 200 grams, bacon 5 grams, lettuce-orange salad 47 grams, prunes 137 grams, coffee 100 grams, sugar 21 grams, cream 25 grams, banana 255 grams.

Sunday, May 22, 1904.

Breakfast.—Banana 220 grams, orange 60 grams, coffee 100 grams, sugar 21 grams, cream 25 grams.

Lunch.—Bread 35 grams, potato 300 grams, fried rice 160 grams, syrup 63 grams, ice cream 84 grams, coffee 100 grams, sugar 14 grams.

Dinner.—Cream of celery soup 100 grams, bread 21 grams, mashed potato 250 grams, spinach 40 grams, French fried potato 100 grams, strawberry short-cake 120 grams.

Monday, May 23, 1904.

Breakfast.—Banana 229 grams, coffee 125 grams, sugar 21 grams, cream 25 grams.

Lunch.—Bread 58 grams, apple sauce 125 grams, scrambled egg 15 grams, consommé 75 grams, fried potato 170 grams, rice croquette 197 grams, syrup 68 grams, coffee 100 grams, sugar 21 grams, cream 30 grams.

Dinner.—Bread 72.5 grams, vegetable soup 100 grams, potato croquette 198 grams, bacon 7 grams, string beans 120 grams, water ice 77 grams, coffee 100 grams, cream 30 grams, sugar 14 grams, banana 270 grams.

Tuesday, May 24, 1904.

Breakfast.—Orange 100 grams, rolls 37 grams, rice 50 grams, syrup 25 grams, coffee 125 grams, sugar 21 grams, cream 50 grams.

Lunch.—Bread 77 grams, cream of celery soup 125 grams, mashed potato 270 grams, tomato sauce 50 grams, farina croquette 191 grams, syrup 78 grams, coffee 75 grams, cream 20 grams, sugar 7 grams.

Dinner.—Bread 49 grams, tomato soup 200 grams, French fried potato 200 grams, spinach 50 grams, farina croquette 276 grams, syrup 100 grams, coffee 100 grams, sugar 14 grams, cream 50 grams.

NITROGEN BALANCE.—Mendel.

Average Intake.

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.

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:

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.