184 COMPARISONS OF RESPIRATORY EXCHANGE. 



of 3.5 per cent, the percentage of the total is nearly the same. The 

 curves for the respiratory quotient show much greater uniformity with 

 the nose-breathing, while the curves for the pulse-rate have approxi- 

 mately the same degree of uniformity with both types of breathing. 

 The respiration-rate is somewhat more uniform with the mouth-breath- 

 ing when the limits of variation are considered as 2.5 per cent, but 

 beyond this there is approximately similar uniformity. The total 

 ventilation of the lungs is much nearer uniformity with the mouth- 

 breathing; this is shown to some extent in the volume per respiration. 



The results of the comparisons would indicate that there is a slightly 

 higher metabolism with mouth-breathing, but that this is due to the 

 fact that the subjects are usually more awake with this type of breath- 

 ing and that this produces a more regular and uniform ventilation. 

 That the volume of air left in the lungs at the end of each expiration is, 

 however, more uniform with nose-breathing is indicated by the greater 

 uniformity of the oxygen consumption and the respiratory quotient with 

 nose-breathing. The variations between the two methods shown by these 

 comparisons with the spirometer unit are so small that either the mouth- 

 piece or the nosepieces may be properly used in respiration experiments. 



MOUTH- AND NOSE-BREATHING WITH THE TISSOT APPARATUS. 



In rest experiments with the Tissot apparatus, nosepieces are ordi- 

 narily used, but in work experiments recently carried out by Amar 1 

 a mouthpiece was employed. Both nosepieces and mouthpiece were 

 used in the comparison study made with the Tissot apparatus and it 

 was therefore of interest to determine the difference, if any, in the 

 respiratory exchange in mouth- and nose-breathing with the Tissot 

 apparatus. A series of experiments with three subjects was therefore 

 made in which the rubber mouthpiece and the Siebe-Gorman noseclip 

 were used in the mouth-breathing periods and the round glass nose- 

 pieces for the nose-breathing periods. Each experiment began with a 

 nose-breathing period, the use of the nosepieces and mouthpiece alter- 

 nating throughout the experiment. The samples of expired air were 

 collected over mercury as in the earlier comparisons with this apparatus 

 and the analyses were made with the Haldane apparatus. No pre- 

 liminary ventilation was obtained, the periods usually beginning within 

 5 minutes of the adjustment of the mouthpiece or nosepieces. The 

 pulse-rate was obtained by means of the Bowles stethoscope, the respi- 

 ration-rate from a pneumograph fastened about the chest, and a record 

 of the degree of muscular repose from a pneumograph placed about the 

 hips. The subjects were all assistants in the Laboratory and were 

 familiar with the apparatus. The statistics of the five experiments 

 in this series follow. 



'Amar, Le moteur humain. Paris, 1914. Journ. de Physiol, et de Pathol., 1913, 15, p. 62. 



