As an index of the reaction of the heart to a definite amount of work, the percentage increase in the pulse-rate 1 minute after work ceases is of interest, this representing in a sense the increment of the pulse-rate expressed in percentages for accomplishing a definite amount of work. This curve shows an extremely irregular contour, the highest point being reached about November 15, the lowest point just before the end of the observations. In comparing the number of minutes required for the pulse-rate to return to the normal after a definite amount of work, it appears that the curve for this factor and that for the percentage increase 1 minute after the ergometer riding are more or less parallel, and this is true until the return from the Christmas recess. After this point the curves are in most instances opposed to each other. It is worthy of note that with the percentage increase 1 minute after work there is a great decrease on the whole after the diet restriction ceases and a high point in the time required for the pulse-rate to return to normal after work, although the absolute maximum is noted on November 14.

Since the gaseous metabolism plays so important a r61e in our study of the total metabolism, the factors entering into the gaseous metabolism, as well as the heat calculations therefrom, are represented by several curves in figure 124.

The average total basal heat production for this group of men per 24 hours may first be considered. Although there are very wide fluctuations from day to day, as indicated by the rise and fall in the curve, the general trend is distinctly downward, save for the high points on November 26 and December 10 following the uncontrolled Sundays and likewise the initial high point following the Christmas recess in the early part of January. Thereafter during January there is a steady decline, with a minimum on January 24 and a tendency to a slight rise thereafter. Since the body-weight was changing throughout the experiment, it is quite obvious that not only the total heat per 24 hours should be considered, but particularly the heat per unit of body-weight and likewise in this homogeneous group of subjects the heat per square meter of body-surface. The curves assigned to both of these factors show remarkable uniformity and agree in the main with the total heat-production curves - a pronounced drop during the first weeks of the season, sharp rises on November 26, December 10, and after the Christmas recess, with a tendency to fall thereafter, and a fair approximation to a level at the end of the period.

When one considers these measurements of metabolism as a whole and the factors of circulation and respiration, it is astonishing what regular pictures they present when compared with the body-weight and, indeed, with the intake of food. The entire picture shows the depression of all activities during the early part of the session, characteristic rises following the recuperation period during the Christmas recess, a rather sharp fall thereafter, with a tendency towards constancy during the month of January. Certain observations that were made after the period of low diet ceased show a pronounced rise in the pulse-rate, lying before riding, the pulse-rate 1 minute after riding on the ergometer, and a very great rise in the body-weight. This implies that the correlation between actual body-weight and these various factors is very close.

It is certainly clear that during the period of transition, when the body-weight was rapidly falling, all of the factors of metabolism and all of the physiological activities were markedly depressed. When the body-weight finally reached a level, namely, during the month of December and the latter part of January, there was a distinct tendency for these activities also to assume a level, although they are by no means absolutely comparable. With the resumption of increased food intake at the end of the experiment, the two factors measured both followed the body-weight, indicating a pronounced increase.

It is also of great significance to note here the two neuro-muscular processes that have been charted, namely, the number of finger movements made in 10 seconds and the eye movements as recorded in the length of time required to move the eye through an arc of 40°. The speed of the finger movements, which has been shown in an earlier research from this Laboratory to be representative of motor coordination, decreased definitely. At about the Christmas recess there was somewhat of a recovery and evidence of a distinct spurt on the last day of the experiment. The eye movements, which have likewise been shown to be characteristic motor coordinations, distinctly increase in the time required for a definite movement from the day when the observations were begun, namely, October 28, to the last day of the series, this increase being progressive and reasonably regular.

The general picture presented by this chart is a depression of the physiological, particularly the metabolic, activities, throughout the greater part of the time. This is likewise true with regard to the two neuro-muscular processes here charted. That these are in large part affected by the state of nutrition is shown by the close relationship between the various curves and the body-weight curves, and, incidentally, the food-intake curve. In view of the close relationship between pulse-rate and metabolism, and in the absence of metabolism measuremerits after the return to normal diet, the great increase in pulse-rate accompanying the great increase in body-weight may legitimately indicate that there was likewise a corresponding increase in the metabolic processes, in all probability closely correlated with the actual body-weight curves. It is important to note, however, that the body-weight curves here have no particular significance per se other than as a general index of the nutritional level upon which the body was living.

Finally, attention must be again called to the pronounced accumulative loss of nitrogen with low diet, averaging for these 9 men 175 grams at the end of the 4 months of the experiment.