468 STATE BOARD OF AGRICULTURE. 



chloroform-air was foiincl to be, at the end of that time, IG^^ times 

 weaker than the checlv. The oxidase was apparently uninjured; some- 

 times it seemed a little more active than in the check. The catalase 

 showed but little injury. 



Hydrocyanic acid gas caused great interference with the activity of 

 the oxidase. For example, three beetles were treated in a cyanide bottle 

 15 hours and then aired one-half hour before being extracted. This 

 extract remained light or whitish in appearance for 2 hours before il 

 began to darken at the surface in contact with the air, and before it 

 would begin to show any indication of bluing guaiac. The check re- 

 quired only about 2 minutes to bring about a decided bluing of guaiac. 

 The catalase-activity was quite strongly interfered with, at first; but 

 the reductase required only about 9 times longer to reduce its methylene 

 blue than the check. 



Extract from beetles kept at 44° to 46° C. for 2i/2 hours, until dead, 

 showed little loss in catalase activity' — but more in its oxidasic and 

 reductase activity. The oxidase was about 7 times slower, and the 

 reductase about 21 times slower than the check. 



Clearlj', the results given by the last method corresponded very well 

 with results obtained by the former method where the effect of the 

 insecticide upon oxidase, catalase and reductase in the ready-prepared 

 extract was studied. It is true that in every case the beetles were killed 

 by the insecticide agent without the entire destruction of any one of 

 the three enzymes — but never without greatly injuring one or more of 

 them. Also, as will be observed, if the reductase were strongly injured, 

 the oxidasic enzymes were usually little injured or apparently not at all ; 

 and conversely, if the oxidase and catalase were greatly injured by the 

 insecticide, the reductase was little injured. Thus, the natural or normal 

 balance of catalase, oxidase and reductase activity was disturbed. 



The question may now be repeated: Is this deleterious effect of the 

 insecticides studied, upon the oxidases, catalases or reductases, the cause 

 of death? It is hardly possible that the three enzyme-like bodies named 

 in the question could be so universally present (with activities so ap- 

 parently coordinated) in tissue extracts and in the living tissues, if they 

 were not of vital importance. They surely accomplish oxidations and re- 

 ductions in the living tissues and much evidence indicates that they 

 are a part, at least, of the machinery of internal respiration. It has 

 been shown that P. cornutus cannot be killed or rendered beyond re- 

 covery, by certain contact insecticides studied, without decided injury 

 to one or more of the three activities — oxidase, catalase or reductase. 

 This fact, taken in connection with what has been shown to be true of 

 the influence of those same insecticides upon the respiratory rate and 

 the respiratory-quotient, supports the view that oxidase, catalases and 

 reductases have to do with the starting and carrying forward of cell 

 respiration. If that view is true, then the deleterious effect of the in- 

 secticides (named in this connection) upon oxidases, catalases or re- 

 ductases in insects must be an important factor — perhaps, in some cases, 

 the determining factor — in causing death. 



No special study has been made of the influence of various contact in- 

 secticides upon the protoplasmic activities which carry forward life- 

 processes in the nervous tissue cells of insects. Such a study in this 

 connection would appear to be of next importance, since all the volatile 



