EXPERIMENT STATION BULLETINS. 437 



extract, was prepared as follows: The insects were thoroughly cleaned 

 with absolute alcohol and a cloth. In the case of Passalus corrmtiis, which 

 was mostly used, the wing-covers and wings were first removed. Then 

 the digestive tracts were carefully removed entire, and discarded. The 

 remainder of the tissues — blood, fat, muscles, nervous tissue, etc. — be- 

 came thoroughly 'Aground up" in a mortar with a little distilled water. 



It will be noticed that the respiratory ratio of the pulp or water 

 extract of insect tissues proved to be rather higher, often, than was the 

 case for healthy, uninjured beetles. A few respiration experiments were 

 run, using insect bodies from which the digestive tracts had been re- 

 moved. The ratio of carbon dioxide given off to oxygen taken up was 

 in this case, also, a little higher usually than the ratio for normal healthy 

 beetles. (See B, table I). Mechanical injury, through crushing without 

 external mutilation, or through pithing the beetles with a hot needle, 

 however, gave a ratio for the respiratory exchange lower than that of 

 healthy normal beetles. But as has already been pointed out, when air 

 saturated with gasoline vapor was used either with the insects them- 

 selves, with the tissue-pulp or with the crude water extract, it regularly 

 caused a decided rise in the respiratory ratio above that given by the 

 same insects, tissue pulp, or crude extract. Thus it began to appear as 

 if whatever bodies were present in the living insect tissues to start and 

 carry forward the respiratory process — these were able to maintain 

 themselves as "respiratory bodies" (with limited activity) for a time, 

 at least, in the insect tissue pulp and in the crude extract of the pulp, 

 where the effects of the insecticides in question might still be studied. 



(b) OXIDASES^ CATALASES AND REDUCTASE'S IN ANIMALS AND PLANTS. 



In the pulp and in the water extract of various tissues of many 

 vertebrate and other animals and in many plant tissues, workers have 

 described enzymes which are able not only to carry forward oxidation 

 processes in the pulp or extract itself, but also to initiate or accelerate 

 the oxidation of certain other bodies, such as gum guaiac, hydroquinone, 

 .tyrosine, etc., when these are added in solution to the extract. Such 

 enzj'mes have received the general name of oxidases. It is not the pur- 

 pose here to give a discussion of oxidasic enzymes, their kinds and pos- 

 sible functions in the living tissues in connection with other enzymes or 

 enzyme-like bodies; but a short statement will make clear the import 

 of the experiments which follow in this connection. None of the oxidases 

 have been obtained in a known pure and isolated form, yet much has 

 been learned of their properties, and of their more or less specific action, 

 so that they have generally received names according to the kind of body 

 or bodies upon which they have been found to act — as alcoholases, alde- 

 hydases, phenolases, or laccase, tyrosinase, etc. Associated generally, if 

 not always in pulp or tissue-extract with oxidases, various workers have 

 found peroxidases, catalases, and reductase (or reductases). The per- 

 oxidases of tissue extracts (when they clearly show themselves present) 

 are substances which activate peroxides — for example they cause hydro- 

 gen peroxide to change in such a way that its oxygen may became trans- 

 ferred to guaiac, causing oxidation of the latter to guaiac blue. Perox- 

 idases serve as activators merely; they do not cause the liberation of 

 free oxygen from the peroxides. Indeed an oxidase is now looked upon 



