EXPERIMENT STATION BULLETINS. 441 



influence upon the ability of the crude extract to oxidize guaiac (exposed 

 to the air) when they were added in small amounts. Both the oxidase 

 and the oxydone were affected. The influence of carbon disulphide, gaso- 

 line, and hydrocj'anic acid gas were studied in the same manner. In the 

 case of carbon disulphide and gasoline, the influence of both the vapor 

 and the liquid of each fluid was studied — using the vapors to saturation 

 in air, and the liquids at the rate of three drops to 2 c. c. of extract 

 thoroughly mixed to an emulsion. 



Carbon disulphide deterred the oxidation of guaiac by the extract 

 greatly; — sometimes the blue coloration did not begin to develop until 

 after two hours, when the extract had been treated with the concentrated 

 vapor or with the liquid for a few hours before testing. The influence of 

 carbon disulphide was most marked when the extract was rich in fat- 

 emulsion. 



The influence of concentrated gasoline vapor on the oxidasic proper- 

 ties of an extract, as studied by the aid of alcoholic guaiac, was never 

 very decided. However, the liquid gasoline first used appeared quite 

 destructive to the oxidase, but that sample of gasoline was later found 

 to be slightly acid in reaction; and when this acidity was rendered just 

 neutral, the liquid gasoline then acted scarcely more harmfully than the 

 concentrated vaj^or. In fact if either the vapor or the liquid gasoline 

 were used with perfectly fresh milky extract (rich in fat) it seemed to 

 hasten the bluing of guaiac — or to hasten the darkening of the extract 

 itself on standing alone in air. 



In the case of hydrocyanic acid gas, it was found that if an extract 

 were tested immediately after being removed from the treatment, the 

 guaiac blued very much more slowly than in the check. If, however, the 

 treated extract were allowed to stand in air for an hour or so until it 

 became free from the odor of hydrocyanic acid, the guaiac blued almost 

 as rapidly upon being added as in the check extract. 



Borax (3 grams in 100 c. c. distilled water) was very destructive to 

 both the oxidase and the oxydone, when a little of the solution was 

 shaken up with the extract and allowed to stand for a few minutes. 



Sodium fluoride, in saturated solution, was used. It retarded the de- 

 velopment of guaiac-blue when added in considerable amounts to an 

 extract, but even 1 c. c. of the solution mixed with 1 c. c. of the extract 

 did not prevent the development of the blue coloration after an hour or 

 two. When added in only small amounts to a fresh extract, sodium 

 fluoride solution seemed to hasten the bluing of guaiac. Likewise chloro- 

 form and ether did not seem to injure the oxidasic activity of the tissue 

 extract toward alcoholic guaiac, except ver}^ slightly when they were 

 used in large amounts and thoroughly shaken up with the extract. 



This study with alcoholic guaiac was instructive, but a method w^as 

 sought which would show by volutne measurements of the oxygen taken 

 up just what influence carbon disulphide and gasoline (for example) had 

 upon the rate at which oxygen was absorbed by insect-tissue-extract plus 

 some other substrate than guaiac. Hydroquinbne solution was selected 

 as the substrate to be oxidized because it was easy to keep a compar- 

 atively constant, clear, standard solution for some time, and because as 

 the oxidation to quinone proceeded, the color of the solution changed 

 progressively from a reddish to a darker and darker coloration. Thus, 

 a color check was afforded, upon the volume of oxygen used in the case 



