448 STATE BOARD OF AGRICULTURE. 



vapor were necessarj' to show a marked influence, especially if the water 

 content of the extract were high. 



After the preliminarj^ tests, written record was kept of more than 

 thirty experiments, including cautionary check experiments, which were 

 made to get the influence of gasoline and carbon disulphide vapors upon 

 the oxygen absorption activity of "'insect extract plus hydroquinoue so- 

 lution". Some of these experiments were performed during as many 

 as three successive periods. In all of these tests unless otherwise stated, 

 the stender dish of each gas-container held 5 c. c. of insect tissue extract 

 from the same stock extract mixed with 2 c. c. of a standard hydroquinoue 

 solution (1.1 grams of hydroquinoue in 100 c. c. of distilled water.) 

 Representative results of these experiments are given in table II. 



The first ten results in the table relate directly to the influence of 

 carbon disulphide or of gasoline vapor upon the activity of ''insect 

 tissue extract plus hydroquinoue solution" for oxygen absorption. 



A study of the table will show that the higher concentrations of 

 insecticide vapors caused a marked reduction in oxygen avidity under 

 that shown by the corresponding checks. Weak concentrations of the 

 insecticides, on the other hand, seemed to accelerate, very slightly, rather 

 than to retard oxygen absorption. One may appreciate the influence of 

 the insecticide, perhaps, better by comparing the total sum of the oxygen 

 absorptions in the insecticide chamber with the total corresponding ab- 

 sorptions in the check gas-chamber. 



In case of carbon disulphide vapor the ratio is 6.7 c. c. to 19.1 c. c. 

 In other words, only about 7/20 as much oxygen was absorbed during 

 the series of tests in the carbon disulphide chamber as was absorbed in 

 the check gas-chamber with air alone present. For gasoline-vapor the 

 ratio is 10.2 c. c. of oxygen absorbed in the gasoline chamber to 13.9 

 c. c. in the pure air chamber (i. e. about 7/10) ; and if those tests in 

 which the vapor was in high concentration are considered alone, then 

 barely over one-half as much oxygen was absorbed in the gasoline-vapor 

 chamber. The ratio of carbon dioxide given off to the oxygen absorbed 

 by the mixture of "insect tissue-extract and hydroquinoue solution" as 

 expressed by' the totals for the insecticide-treated samples is 0.8+, and 

 the similar ratio as expressed by the totals for the corresponding checks 

 is 0.4. That is, the respiratory ratio of the "tissue-extract plus hydro- 

 quinoue solution" proved to be decidedly higher in the presence of strong 

 gasoline or carbon disulphide vapors than was found to be the case in 

 pure air. Now, as has already been mentioned, an oxidase in the insect 

 tissue-extract is able, it is believed, to accelerate the oxidation of hydro- 

 quinoue to quinone and water — the quinone showing its presence by its 

 odor and by a change in color of the extract-solution. If, then, an 

 oxidase in the extract does cause that kind of an oxidation of hydro- 

 quinoue, it would naturally follow that an extract to which the latter 

 had been added might take up more oxygen in a given period than it 

 otherwise would, and that the added hydroquinoue would therefore de- 

 crease the respiratory ratio (-^0 of the extract. Note the ratio 0.4 

 above, which is much below that found for healthy beetles in pure air — 

 the latter ratio being about 0.75. The last three results given in Table 

 II are precautionary checks on the manner in which hydroquinoue is 

 oxidized by extract of the tissues of P. cornutus. To each of the stock 



