GAS INTERCHANGE. 



71 



The number of experiments is not large enough to select very complete 

 series, but they show agreement with the special temperature series already 

 considered. 



This matter has been discussed at some length, since, in the tables which 

 follow, the experiments have been arranged on the basis of gas-interchange 

 ratios and only secondarily according to temperature, so that owing to indi- 

 vidual variation the real temperature effects are sometimes masked. 



In summing up the effect of temperature on the respiratory gas interchange 

 it may be said that the amount of carbon dioxide given off rises measurably 

 in accord with the van't Hoff generalization regarding reaction velocities, 

 while the increase of absorption of oxygen is somewhat less. As a consequence, 



the -Q7 2 quotient tends to rise with ascending temperatures. 

 GAS INTERCHANGE RATIO AND ACIDITY. 



When the whole mass of experiments made during the summers of 1912 and 

 1913 from material in its natural habitat is arranged according to the gas- 

 interchange ratio, quite irrespective of whether the material was young or old, 

 turgid or flaccid, and without regard to temperatures, we get the general 

 averages given in table 47. 



TABLE 47. General average of 104 gas-interchange determinations with accompanying acidities 

 arranged without regard to temperature, but grouped under the C0 2 /O 2 ratios. 



With rising ratio there is rising acidity until, when the acidity is highest, 

 the gas-interchange quotient is slightly more than unity. In other words, the 

 evolution of carbon dioxide is a little in excess of the absorption of oxygen. 

 At the other end of the scale, where the acidity is lowest, the average evolution 

 of the former was only one-third of the absorption of the latter. In indi- 

 vidual experiments there is, of course, considerable variation. Experiment 

 32 (table 60) showed an initial acidity of 2.32 for the pure juice, which was the 

 highest obtained, and of 5.75 per gram dry weight, giving as its average ratio 

 almost exactly 1.00. The highest ratio obtained, however, was 1.32 (experi- 

 ment 44a, table 60), from material the initial acidity of which was 0.81 per cubic 

 centimeter pure juice and 2.05 per gram dry weight. On the other hand, the 

 highest total acidity per gram dry substance, namely, 7.85, had only a pure- 

 juice acidity of 1.57, and gave a gas ratio of no more than 0.88. Similarly, 

 another group of experiments, 39 et seq., with the very high initial total acidity 



