ALVEOLAR CARBON DIOXIDE. 489 



Examining first the values drawn from the calculated carbon- 

 dioxide tension (column h), we find with Bro a decided fall of approxi- 

 mately 20 c.c. per minute, with Can, Gar, and Gul a decrease, while 

 with subject Mon there was a tendency for this value to remain con- 

 stant. With Moy there was an increase from 104 c.c. to an average 

 not far from 116 c.c. With Pea, Tom, and Vea, on the con- 

 trary, there was the usual fall, and with Pec practically constant 

 values. In general, the values based upon the calculated alveolar 

 carbon dioxide show a clear tendency to a somewhat less ventilation 

 of the lungs per millimeter of carbon-dioxide tension. 



In comparing the calculations based upon the direct determinations 

 of alveolar carbon dioxide, which, unfortunately, were not obtained 

 until after the middle of November, we find that no pronounced or 

 regular change in the ventilation per millimeter is apparent with Bro, 

 Can, Kon, Gar, Gul, Mon, Pec, or Tom. (See column i.) On the 

 other hand, Moy's values show a tendency to fall, although high 

 values are found in the early part of January. The values for Pea 

 tend to decrease, as do those obtained in one month's observations 

 with Spe. The general picture with Vea is similar, although high 

 values are again found in the early part of January and the results 

 with him on the whole are irregular. 



One must conclude, therefore, that the tendency shown by both 

 sets of figures is, in certain cases, for the ventilation per minute per 

 millimeter of alveolar carbon-dioxide tension to be somewhat lower 

 at the end of the period of reduced diet than at the beginning. In 

 other words, the respiratory center is somewhat less sensitive at 

 the end than before the reduction in diet began, this decrease in sen- 

 sitivity being due to the low diet. This is in contrast to the results 

 reported by Loewy and Zuntz.^ No change was found with Loewy, 

 and although variations with Zuntz had been found from time to time 

 during a series of years, as a matter of fact the ventilation per milli- 

 meter of alveolar carbon dioxide in the experiment with the war diet 

 was exactly that found with him 28 years before. Their general con- 

 clusion is that the low diet did not increase the sensitivity of the 

 respiratory center. 



Dr. T. M. Carpenter calls our attention to the fact that with a 

 decrease in respiration rate as shown in a previous section there would 

 be a decrease in the total ventilation, because the personal dead space 

 of the subject would not have to be swept out so many times with a 

 slower respiration rate. This, together with the fact that there was 

 less carbon dioxide to be eliminated, naturally resulted in a lower 

 total ventilation, so that with a fairly constant level of carbon-dioxide 

 tension there would result mathematically a lower volume of expired 



* Loewy and Zvintz, Berl. klin. Wochenschr., 1916, 53, p. 825. 



