TABLE 119.-Efficiency of M. A. M. in respiration experiments with bicycle ergometer.1 [Basal values obtained in no-load experiments, without motor.] 1 Ergometer I was used for all experiments up to Jan. 19, 1912, inclusive; ergometer II was used for the experiments subsequent to that date. to make the best selection of no-load experiments for comparison. While, therefore, it is necessary to disregard the individual periods, a general deduction can be made from the results as a whole that the percentage efficiency as computed on this basis gradually increases with the load, the average efficiency for the whole table being not far from 30 per cent. Disregarding individual periods with extraordinarily high values, the maximum efficiency was approximately 33 per cent. These values are unquestionably higher than they would have been had the subject been able to relax the muscles completely in the no-load periods. They should accordingly be taken with considerable reserve. EFFICIENCY IN WORK EXPERIMENTS BASED ON VALUES OBTAINED IN NO-LOAD EXPERIMENTS WITH A MOTOR-DRIVEN ERGOMETER. It would appear at first sight as if the energy required by the subject to drive a machine without resistance would be a suitable base-line to use in finding the increase in metabolism and measuring the efficiency of the subject when riding with load. If it were possible for the subject to rotate the pedals evenly and without undue strain this would be true, but unfortunately the subject M. A. M. found it extraordinarily difficult to ride without load, and complained continually of his inability to maintain an even pace, our obser vations of the tension on the sprocket chain fully confirming his personal impression. Inasmuch as the values obtained were unquestionably higher than normal owing to this extraneous muscular activity, the attempt was made to obtain a more even revolution of the pedals by belting a motor to the rear wheel of the ergometer and driving the machine at varying rates of speed. In these experiments, which were made only with ergometer II, the subject endeavored to sit in a relaxed position, and allow the legs to move freely with the rotation of the pedals. The results are singularly indicative of an inability to relax completely, and show a continuous opposition to the work of the motor. Since the motor was used in relatively few no-load experiments and the rate of speed did not vary widely, the number of experiments which can be compared with the work experiments is much smaller than was used for the other comparisons. They have, however, been collected and presented in table 120. In table 120 the values are given chronologically in order to compare the results obtained with the different rates of speed. On nearly every day the subject rode at two rates of speed, but unfortunately the rate was on some days so great as to make a comparison with the work experiments impossible, since no riding experiments at these speeds were available. On the other hand, the comparisons given are sufficient to show clearly, first, that the average efficiency for all the experiments is not far from 27 per cent; and second, that there is a marked difference in the results with a change in the rate of revolution, the efficiency almost invariably decreasing with the high rate of revolution. Since it is believed that in the no-load experiments the values found were all too high, we must accept with considerable reserve the average value of 27 per cent for the efficiency as computed on this basis, and the fact should be clearly recognized that the percentage of efficiency was raised by many extraneous muscular movements, such as "back pedaling," which would have been absent in a work experiment. In this table, as in others, individual periods will be found that give abnormal results, but as before the results should be considered only as a general picture. Such a review of the results does not lead one to the conclusion so strikingly shown in the earlier tables, namely, that the efficiency increases with the load; on the contrary, the values appear to show the reverse. The values are, however, particularly significant in indicating the great variations due to alterations in the rate of speed. It will be noted that with one or two exceptions all the values of 29 per cent or above were obtained with the revolutions per minute not greater than 92. The method of determining the base-line is, however, open to such severe criticism that values computed in this way must be taken with great reserve. EFFICIENCY IN WORK EXPERIMENTS BASED UPON VALUES OBTAINED WITH A CURRENT OF 0.5 AMPERE. An inspection of the preceding tables shows at a glance the difficulties incidental to assuming a base-line other than lying, for the extraneous muscular activity incidental to sitting up or to riding with no load, either with or without motor, certainly calls for a greater metabolism than would be expected when no external muscular work is done. Our reasons for believing TABLE 120.-Efficiency of M. A. M. in respiration experiments with bicycle ergometer II. [Basal value obtained in no-load experiments, with motor-driven ergometer.] this have already been freely mentioned in the previous discussions. It seemed desirable, therefore, that experiments should be made in which the subject should perform light work, sufficient in amount to insure a reasonably regular rotation of the pedals, and to eliminate all tendency to back pedal or to race. Accordingly a series of experiments was carried out in which the current through the armature was adjusted at 0.5 ampere. This was a very light load, and, indeed, somewhat lighter than the subject really preferred for comfort and complete muscular coördination; nevertheless there was considerably more resistance than with "no load" and the results furnish a reasonably constant base-line. In other experiments the subject rode with the resistance produced by a current of 1.5 amperes, and a comparison can logically be made of the results obtained in all experiments with these two resistances in which the revolutions per minute were essentially the same. TABLE 121.-Efficiency of subjects in respiration experiments with bicycle ergometer with a current of 1.5 amperes. [Basal values obtained in experiments with current of 0.5 ampere.] 1 Average of results obtained in the experiment of Mar. 16 with this subject. In discussing the previous tables, it has been pointed out frequently that there appeared to be some intimate relationship between the speed and the total amount of work performed, and the results show that only experiments with constant speed should be compared. Accordingly in table 121 we have included only those experiments with the different subjects in which essen |