488 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



to day are more to be relied upon than are those directly determined. 

 Consequently we may compare, with an even greater degree of con- 

 fidence, the relationship between the calculated values for the alveolar 

 carbon dioxide at the beginning and end of the long period of under- 

 nutrition to see what effect the undernutrition had upon the alveolar 

 carbon dioxide. 



Comparing the one or at most two observations before the diet with 

 the average of the last 3 days of the low diet, we find that with Bro, 

 Can, Gar, and Pea there was practically no change, with Gul a slight 

 tendency for an increase at the end, and with Mon and Moy a slight 

 decrease. With Pec there was a distinct falling off in the alveolar 

 carbon dioxide, with Tom no material change, and with Vea possibly 

 a slight increase. From a comparison made on this basis, it is difficult 

 to note any particular alteration in the alveolar carbon dioxide due to 

 the altered dietetic conditions, there being no decided tendency, on 

 the average, for the alveolar carbon-dioxide tension to change even 

 after extensive dietetic alterations. 



ALVEOLAR CARBON DIOXIDE AND IRRITABILITY OF RESPIRATORY CENTER. 



As Loewy and Zuntz^ point out, unusual significance attaches to 

 the alveolar carbon dioxide since the reaction of the respiratory center 

 to the alveolar carbon dioxide may be taken more or less as an indica- 

 tion of the irritability of the organism. It has been their custom in 

 many of their respiration experiments to compute the relationship 

 between the alveolar carbon dioxide and total ventilation of the lungs, 

 i. e., to express in cubic centimeters per minute the amount of ventila- 

 tion, not reduced, per millimeter of carbon-dioxide tension in the lungs, 

 and such determinations were made in their experiment on war diet. 



Similar computations for our experiment seemed desirable. These 

 have been made on two bases: first, from the alveolar carbon dioxide 

 as actually determined, and second, that found by calculation. The 

 ventilation per minute was obtained by dividing the observed ventila- 

 tion (see column a) by the tension of carbon dioxide, either determined 

 or computed. The results are recorded in cubic centimeters per 

 minute per millimeter of carbon-dioxide tension in columns h and i, 

 the first being computed from the calculated carbon-dioxide tension 

 and the second from the direct determinations. Bearing in mind the 

 facts that no pronounced tendency was found for the alveolar carbon 

 dioxide to change during the experiment and that in general there was 

 a distinct tendency for the total ventilation of the lungs to become 

 lower as the experiment progressed, one is prepared to find that the 

 ventilation per minute per millimeter of carbon-dioxide tension has a 

 definite tendency to decrease as time goes on. 



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



