GAS INTERCHANGE. 



67 



temperature group among the experiments on turgid joints the ratio rises 

 very greatly. With flaccid joints there is a general tendency to have a great 

 oxygen absorption, which shows also in the averages, so that the gas ratio is 

 necessarily lower. Attention should be called, however, to the fact that no 



conclusions should be drawn from this table as to the relation of temperature 



r^o 

 and the ^p quotient, since neither the amount nor the course of the various 



acidities have been taken into account in making these averages. It will de- 

 velop, from the more specific analysis of the results which is to follow, that these 

 considerations are of no small importance. The purpose of this table is to 

 indicate in a general way the difference in activity of the three classes of tissues. 



TABLE 42. Evolution of C0 2 and absorption of 2 in relation to temperatures. 



Evolution of CO 2 and absorption of Oi in relation to temperature, arranged without regard 



CO> 



to the -J7v-= ratios; averages of 104 gas-interchange experiments, made during the summers 



of 1912 and 1913. 



The amount of carbon dioxide given off is not as much as that formed by 

 the typical plant, but the disparity is by no means as great as would be sup- 

 posed from the statements that are usually made. Indeed, in the young tissue 

 the evolution of carbon dioxide is decidedly rapid. In order better to make 

 comparisons it is well to estimate the results by weight rather than by volume. 

 Reducing those given in table 42, where the quantities of carbon dioxide are 

 expressed in cubic centimeters, by multiplying by the appropriate factor for 

 the weight of the gas at different temperatures and at the barometric 

 pressure for Tucson (see description of methods), we have (in table 43) 

 the amounts in terms of milligrams per gram tissue per hour. The amounts 

 are in as close agreement with the results indicated by the Pettenkofer 

 method as would be expected and as may be seen by reference to table 28, 

 on page 55. The young tissue at 31 to 36 C. loses in 24 hours approxi- 

 mately 0.8 per cent of its fresh weight or 4.5 per cent of its dry weight in 

 carbon dioxide. At the same temperatures, the old turgid joints show a loss 

 of about half that amount in their fresh weight, but less than a third when 

 reckoned for dry weight. At 40 to 41 C. their activity is somewhat greater 



