. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 124 LEIGH E. CHADWICK AND CARROLL M. WILLIAMS cause the frequency of wingbeat to rise above the value in air by supplying a greater than normal proportion of oxygen. 4. Helium-oxygen mixtures Having found no correlation between the tension of oxygen and the response of the insect to pressure, there remained the problem of distinguishing between the two other variables involved in these experiments; namely, gaseous density and pressure per se. Their separation seemed difficult at first, since the density and total pressure of
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 124 LEIGH E. CHADWICK AND CARROLL M. WILLIAMS cause the frequency of wingbeat to rise above the value in air by supplying a greater than normal proportion of oxygen. 4. Helium-oxygen mixtures Having found no correlation between the tension of oxygen and the response of the insect to pressure, there remained the problem of distinguishing between the two other variables involved in these experiments; namely, gaseous density and pressure per se. Their separation seemed difficult at first, since the density and total pressure of a given gas mixture are directly proportional. However, the fact that helium is an inert gas with a density only about one-seventh that of nitrogen offered a means of attacking the problem. Using helium and oxygen, mixtures 420 400 D REPLETA AT 25' G IN AIR O IN 147% 02 IN N2 • 0 VIRILIS IN AlR AT 259° C » AT 193' C « LINE OF SLOPE -033. I -0 08 -0 04 LOG ATMOSPHERIC DENSITY 0 00 GRAMS PER LITER 0 04 FIGURE 4. Wingbeat frequency of D. repleta and D. i>irilis as a function of atmospheric density. Solid lines fitted to empirical data by the method of least squares. Broken line of slope — added for comparison. may be prepared which differ from air or other oxygen-nitrogen mixtures in density but not, presumably, in regard to most other properties which are physiologically significant. Two helium-oxygen mixtures were used for this purpose, one containing per cent oxygen, the other per cent. At 25 degrees C. and one atmosphere, the densities of these mixtures, both of which contained water vapor and small amounts of nitrogen, were approximately and grams per liter, respectively, as compared with grams per liter, the density of moist air. Frequency of wingbeat was measured with D. repleta in each of these mixtures throughout most of the range of pressures with results recorded in Table 6 and Figure 3. It is evident that the frequency was
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
