450 STATE BOARD OF AGRICULTURE. 



extracts (before samples for the tests were taken) four drops of weak 

 ammonia (0.9 sp. gr. diluted live times) were added. This ammonia 

 had the effect to reduce the carbon dioxide excreted to a very small 

 amount.* The influence of oxidase in causing the hydroquinone to take 

 up oxygen in the manner described might therefore stand out promin- 

 ently. The total oxygen taken up and the total carbon dioxide given 

 off in each case is given in the table, and although the ammonia used 

 kept the ratio (-q^^ = |-^j down to 0.35 in the extract containing no 



by the increased amount of oxygen used in the extract plus hydro- 

 quinone mixture. The larger value of the ratio of = . 8, as found above 

 for the "extract plus hydroquinone" in the insecticide chamber, must 

 therefore point to the fact that the gasoline and carbon disulphide vapors 

 used were able in some unknown manner to inhibit or lessen the acceler- 

 ating (catalytic) action of the extract-oxydase in bringing about the 

 oxidation of hydroquinone. A further precaution which was observed 

 should be explained here. Tissue-extract was brought to a boiling tem- 

 perature (about 15 to 20 minutes) to destroy the oxidasic enzymes. It 

 was then allowed to cool and the regular amount of hydroquinone solu- 

 tion was added. Tests were then made using the apparatus as in other' 

 experiments, and no measurable amount of oxygen was taken up during 

 longer periods than any used in the regular experiments. It has already 

 been explained that the hydroquinone stock solution would remain clear 

 for days. HoAvever, if the heated "extract plus hydroquinone mixture" 

 had been scarcel}^ brought to the boiling temperature or had been heated 

 only a short time before it was allowed to cool, it often showed a very 

 slight reddish or cherry tinge after twenty-four to thirty hours — indicat- 

 ing that the heat had not been sufficient to destroy quite all of the 

 oxidasic activity. Thus, the appearance of this peculiar reddish brown 

 color was an even more delicate test of the oxidation of hydroquinone 

 than the volumetric measurement of the oxygen used, and mention has 

 already been made of how the reddish brown tinge deepened progressively 

 as hydroquinone became oxidized to quinone. It was interesting and 

 confirmatory, therefore, to note that in all ten of the experiments listed 

 in table II the deeper color was found to be in the stender dish of that 

 gas container where most oxygen had been taken up. One must see 

 that in the extracts used, a slight respiratory exchange exists, and the 

 influence of the insecticide agents upon this exchange has not been 

 eliminated; but the respiratory exchange in such a treated extract (a few 

 hours old) is very low indeed as sho^ii by the COo given off — and the 

 evidence just enumerated leaves no doubt that in studying the compar- 

 able oxygen measurements, we see mainly the influence of the agents in 

 question upon the oxidase activity toward hydroquinone. Two experi- 

 ments (not recorded in table II), carried at once for short periods with 

 gasoline vapor in high concentration, gave results contradictory to all 

 the rest as far as gas measurements were concerned — that is, the meas- 

 urements seemed to show that most oxygen had been taken up in the 



*Sec effect of ammonia on I ,-.— )■ Tech. Bulletin 11. 



