BATES.

DAVIS.

Any elaborate discussion of the individual results, tabulated in the foregoing tables, seems hardly necessary. To any one interested in the details of the work, a study of the tables themselves will give the necessary information. It may be well, however, to emphasize at once a few of the fundamental points most striking in character which bear upon the main problem. Take, for instance, the case of Oakman, where the data are recorded for every day from October 4, 1903, to April 4, 1904. The degree of proteid metabolism, as indicated by the excretion of nitrogen through the kidneys, is here shown for each day of the six months. Up to November 3, practically for a month, there was not observable any very noticeable change in the rate of proteid metabolism, but commencing with November 4, the nitrogen excretion dropped very rapidly, and as one glances through the daily records for month after month, it is seen that the daily nitrogen output through the kidneys fell to 6 to 8 grams per day, with a daily average excretion of 7.42 grams of nitrogen, as figured from October 21 to April 4.

Further, it will be noted that while the body-weight gradually declined during the first three months, falling from 66.7 kilos down to 62.3 kilos on January 18, from that date on to the close of the experiment the body-weight was practically constant. Here, then, we see, under the use of a prescribed diet quite sufficient in amount to satisfy the cravings of the appetite, a lowering of proteid metabolism equal to that obtained by the individuals of the preceding group. Again, if the body-weight of Oakman is placed at 64 kilos, as representing the average between the initial body-weight and the weight during the last three months, it will be found that the output of metabolized nitrogen per kilo of body-weight amounted to 0.116 gram; not widely different from similar data obtained with men of the preceding group.

Moreover, these results obtained with Oakman are practically duplicated by every other member of this group of soldiers detailed from the United States Army. No exception whatever is to be seen, but every man shows the same lowered proteid metabolism, with practical maintenance of body-weight, with complete satisfying of the appetite, and without loss of health, strength, or vigor, as will be enlarged upon later.

While in the case of Oakman, the nitrogen excreted was determined by an analysis made each day, in the case of the other men of this group the data are given mainly for weekly periods; the results being expressed, however, in the average daily amount for each seven days’ period. By comparing the figures for the daily excretion of nitrogen with the daily dietary, it is easy to trace out the influence of the changes in diet on the extent of nitrogen metabolism.

In considering the changes in the rate of proteid metabolism shown by all the members of this group, it will suffice for present purposes to deal mainly with the average results.

Compare now the average daily output of nitrogen through the urine from November 1 until April 4—a period of five months—of each of these men.

AVERAGE DAILY OUTPUT OF NITROGEN.

The figures given show an astonishingly low proteid metabolism for the five months’ period; 7.5 grams of nitrogen in the day’s urine correspond to 46.8 grams of proteid metabolized, while 8.5 grams of nitrogen mean the metabolism of 53.1 grams of proteid. In other words, all of these men during a period of five months practically averaged a daily output of nitrogen through the kidneys corresponding to the metabolism of less than one-half the 105 grams of absorbable proteid called for by the so-called standard diets. Further, close scrutiny of the results in the individual tables shows that during many weeks much lower results were obtained than is indicated by the general averages.

Just here emphasis should be laid upon one fact, doubtless of primary importance in any modification of the rate or extent of metabolism in any individual, viz., that in this experiment the daily diet was prescribed, thereby taking from the individual freedom of choice in the selection of food. The writer has no question in his own mind that an intelligent choice of food, coupled with the satisfying of a natural or acquired appetite in moderation, will lead to better results than any system of prescription as to what shall be eaten each day and in what quantity. Still, this is the method necessarily made use of in the present experiment, the writer having prescribed the character and amount of each meal throughout the entire six months’ period, with due regard, of course, to the expressed likes and dislikes of the men.

One feature in the diet compelled by the circumstances of the case also needs to be referred to, namely, the necessity of keeping the men thoroughly satisfied, so that there should be no feeling of hunger, no craving for food. With a person interested in the experiment and desirous of ascertaining the effect of a low nitrogen intake, there would naturally be a willingness to endure, if necessary, for a time some personal discomfort; but with this detail of the United States Army it could not be expected that the men would remain satisfied if they were compelled to undergo the pangs of hunger even for a day or two. Consequently, it was necessary in prescribing the daily diet to see that the quantity of the food was such as to completely satisfy the appetite. This necessitated the use of considerable bulky food of low fuel, and low nitrogen, value. In this way only was it feasible to reduce the nitrogen intake, as well as the fuel value of the food, to the desired level. Practically during the entire six months’ period, with the possible exception of a few days, the men were given sufficient food to completely satisfy their appetites. Throughout the entire period of the experiment, the men all manifested a keen appetite and utilized their food to good advantage, with establishment of the nitrogen metabolism indicated by the foregoing results.

Still confining our attention to the average results regarding nitrogen excretion, we may ask the question, what was the excretion of metabolized nitrogen per kilo of body-weight in the different individuals? This is easily calculated and the data are shown in the following table, in which the figures standing for body-weight are either the data for the month of April, 1904, or else the average between the October and April weights, as in those cases where the body-weight fell off during the experiment.

Scrutiny of these results shows that the daily excretion of metabolized nitrogen ranged in this period of five months from 0.106 gram per kilo of body-weight up to 0.150 gram per kilo of body-weight. Since these men were on essentially the same diet, it is obvious that there were some peculiarities, or personal idiosyncrasies, that tended to modify the exact extent of proteid metabolism, and in some cases at least constituted a more potent factor than body-weight in determining the rate of metabolism. This fact is clearly emphasized in the case of Morris, who, with a body-weight of 59 kilos, showed a proteid metabolism equivalent to only 7.03 grams of nitrogen per day, and Coffman, who, with a body-weight of 58 kilos, showed under the same conditions an average excretion of 8.17 grams of nitrogen per day.

What was the effect of this lowered proteid metabolism upon the bodily condition, especially body-weight? To answer this question the weights of the men are given in the following table, the one column of figures showing the body-weight at the commencement of the experiment, the other column showing the weight at the close of the experiment.

TABLE OF BODY-WEIGHTS.

Comparison of these figures shows that six of the men were practically of the same body-weight at the close of the experiment as at the beginning. Of the others, Oakman, Fritz, Cohn, and Bates lost somewhat. Bates, however, was quite stout, and the work in the gymnasium as well as the change of diet tended to reduce his weight. In fact, with the possible exception of Oakman, the slight loss of weight these latter men underwent was a distinct gain to their bodily condition. The most significant feature, however, is to be found on scrutiny of the tables of results for each man, where is seen the body-weight for each day of the six months. Here it will be noticed that, as the experiment progressed, there was, as a rule, a tendency for the body-weight to increase; this was followed by a decline, after which the weight remained practically stationary. This is well illustrated in Oakman’s case. Starting with a body-weight of 66.7 kilos on October 4, he reached 67.6 kilos on November 29, then declining in weight to 62.3 on January 18, after which he remained practically stationary, or varied only within narrow limits.

Finally, it should be said that the low proteid metabolism on which these men were apparently maintaining body-weight was not associated with any increase of non-nitrogenous food. At no time did the fuel value of the daily food reach 3000 calories; in fact, about January 12 the average fuel value of the food was only a little over 2000 calories per day.

First Nitrogen Balance.

Early in January, the body-weight of the men having become practically stationary and the proteid metabolism, as measured by the output of metabolized nitrogen, having been reduced to a low level, an attempt was made to see if the men were truly in a condition of nitrogenous equilibrium. A six-day period was used, during which all the food for each meal was carefully analyzed, the nitrogen in every sample of food being determined in duplicate by the Kjeldahl-Gunning process. The fæces of the period were separated by lampblack, given at appropriate times in gelatin capsules, and all necessary precautions observed to insure an accurate nitrogen balance. The accompanying tables of results give all the necessary data.

The average nitrogen intake per day was 8.23 grams, and the average fuel value of the food per day was 2078 calories. These are the figures for Oakman. With some of the other men there were slight variations from these figures, as shown in the tables—owing to slight variations in diet. Without exception, all the men showed a minus balance, indicating that on this diet the body was losing nitrogen. In other words, the diet as a whole was insufficient for the needs of the body in every case. Whether this was due to lack of sufficient proteid or to an insufficient amount of fat and carbohydrate, i. e., a too low fuel value, cannot be said definitely, but there is every reason to believe that the amount of non-nitrogenous food was insufficient to furnish the requisite fuel value, and consequently body proteid was drawn upon to supply the deficiency. The loss of nitrogen to the body per day varied as a rule from 0.5 to 2.0 grams. In one case only, viz., Broyles, was there a close approach to a balance. In his case there was a minus balance of only 0.12 gram of nitrogen per day.

The average daily output of nitrogen through the urine for this six-days period (Oakman’s case) was 7.52 grams.