486 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



An examination of the relationship between the progress of the 

 experiment and the maximum volume does not show any uniformity. 

 While, with a certain number, the maximum volume is to be found at 

 the beginning of the experiment, with three of the men it is noted as 

 late as January 9 or thereafter. Similarly the appearance of the 

 minimum is not uniformly noted. Aside from the value for Fre, 

 which is liable to misconception, owing to the shortness of the time 

 in which he was studied, we still have a minimum value appearing 

 with Mon as early as October 19. With Bro, Can, Kon, Gar, Gul, and 

 Pea the minimum occurs during the last half of January. 



These measurements, it will be recalled, all refer to the total volume 

 per respiration and were usually averaged from 100 or more respira- 

 tions. Hence the actual maximum and minimum figures are of 

 significance. The highest volume per respiration, 634 c.c, was noted 

 with Gul on October 1 and 20. The absolute minimum, 346 c.c, was 

 noted with Pea on January 24, 1918. Undue stress should not be 

 laid upon either the minimum or maximum results, for obviously their 

 significance is chiefly in the relationship to the respiration rate existing 

 at the time. In general the volume per respiration of these subjects 

 appears to be well within normal limits, with perhaps a slight tendency 

 towards low rather than high values, when compared with normal 

 subjects of similar age previously studied in this Laboratory. 



ALVEOLAR CARBON DIOXIDE. 



The physiological significance of the alveolar carbon dioxide has 

 been emphasized in practically all studies of the respiration in recent 

 years. The delicacy of the regulation of the mechanism for respira- 

 tion and the important role played by alveolar carbon dioxide are be- 

 coming increasingly evident. Although in the earlier stages of the 

 investigation sufficient data were secured in the respiratory studies 

 to compute the alveolar carbon dioxide by assuming a constant dead 

 space, we deemed it important to make direct studies of this factor. 

 TJnfortunately these studies were not begun until about the middle of 

 November. Thereafter direct alveolar carbon-dioxide determinations 

 were carried out by the method outlined on page 79 in connection 

 with each experiment with the respiratory-valve apparatus. The 

 technique used gives results^ comparable to those obtained by the 

 Plesch-Higgins^ method, and consequently the values approach the 

 carbon-dioxide tension of the venous blood rather than that of the 

 arterial blood. These values are recorded in column g of table HI. 

 In almost every instance they represent the average results of two well- 

 agreeing determinations obtained immediately after the respiratory- 

 exchange experiments, the subjects being always under uniform condi- 



iRoth, Boston Med. and Surg. Journ.. 1918, 179, p. 130. 

 'Higgins, Carnegie Inst. Wash. Pub. 203, 1915, p. 171. 



