192 METABOLISM DURING WALKING. 



ing for this disparity in amount of work, the apparent difference be- 

 tween the series of tests is reduced to about 1 per cent, which may well 

 be stated to be within the limits of experimental error and not suffi- 

 ciently pronounced to indicate a real physiological difference in the 

 two methods of preliminary breathing. 



Owing to the fact that a slightly larger amount of work was usually 

 performed in the second test of each comparison set, i. e., when the 

 experiment was preceded by but 15 seconds of breathing through the 

 mouthpiece, the slightly larger oxygen consumption notsd in these 

 periods (see tables 16 and 49) may be explained without attributing it 

 to the type of respiration preceding the experiment. In the hope that 

 a study of the rate of oxygen consumption from minute to minute 

 might throw some light upon the effect of mouthpiece breathing, such 

 computations from the kymograph curves during grade-walking tests 

 were made. The results which are not tabulated, showed no decided 

 change in the oxygen consumption nor any marked alteration in the 

 rate of absorption at the beginning of the period. The variations are, 

 in a number of cases, very large and are probably due to errors in the 

 estimation of the time from the slope of the curve errors which are 

 fundamental to the method. The evidence of both the total per minute 

 values in tables 16 and 49, and the values calculated from the kymo- 

 graph curves, suggests no appreciable difference in the rate of oxygen 

 consumption in the two series of tests which is not substantially 

 accounted for by the small difference in the amount of work done. 



CONCLUSIONS WITH REGARD TO THE EFFECT OF LONG AND SHORT PRELIMINARY MOUTH- 

 PIECE BREATHING. 



A close study of the respiration-rate, pulmonary ventilation, and 

 oxygen consumption shows no appreciable differences between the two 

 types of preliminary biea thing other than what can reasonably be 

 ascribed to the unfortunate but unavoidable slight differences in the 

 amount of work done. On the other hand, it is quite clear that the 

 respiratory quotient is materially affected by the type of respiration, 

 particularly in the walking experiments, being almost invariably much 

 lower with the short preliminary mouthpiece breathing. 



One would normally assume that with the long preliminary breath- 

 ing there would have been a period of adjustment, so that with the be- 

 ginning of the metabolism measurements the amount of carbon dioxide 

 exhaled would be essentially that produced. Immediately after the 

 insertion of the mouthpiece, particularly if there is any adjustment of 

 the respiration to the new conditions, as there usually is, one can expect 

 either an excessive removal of carbon dioxide due to pumping-out 

 or possibly the storage of carbon dioxide due to a reduced ventilation. 

 The former is usually the case, and it can be easily seen that the amount 

 of carbon dioxide exhaled would then be larger than that actually 



