EXPERIMENT STATION BULLETINS. 459 



long continued drying injures that ability. A temperature of 59° C. 

 for 10 minutes is sufficient, usually, to destroy almost all the catalase 

 activity in the pulp or crude water-extract from this beetle, leaving the 

 oxydasic power of the same pulp or extract still very active toward 

 guaiac or tyrosin. Sometimes an extract was found to show a little 

 greater resistance to heat; and in any case, if one wished to be sure of 

 destroying absolutely all catalase activity toward hydrogen peroxide, so 

 that small bubbles of oxygen would not appear even after several hours, 

 a temperature very near the boiling point was required. It was possible 

 to separate the soluble catalase from its solution but not to free it from 

 proteins. The catalase was carried down with the protein precipitate by 

 either half or full saturation with ammonium sulphate or with the Yjre- 

 cipitate by alcohol; and the precipitate from full saturation with am- 

 monium sulphate was found to contain practically all of the catalase. 



In making a quantitative study of the influence of insecticide agents on 

 the catalases one could obtain a little more uniformly constant results 

 by using a fairly clear solution in which any insoluble particles present 

 would be extremely fine, so that they would remain in suspension for 

 hours. The results given in Table V are therefore taken from a study 

 of the influence of certain agents upon the catalases in such an extract 

 solution from the tissues of P. cornutus. The beetles were extracted 

 in the usual way (i. e. digestive tract removed, etc.), using distilled water 

 at the rate of about 12 c. c. to 5 beetles. The crude extract was filtered 

 through linen of very fine mesh. Two cubic centimeters of this filtrate 

 were then measured out and diluted to 10 c. c. with distilled water. 

 In this way an almost clear dilution was obtained in which the fine 

 particles remained in suspension for hours; and by agitating the dilu- 

 tion just before dividing it, one could obtain entirely uniform samples. 

 In every test, 2 c. c. of this diluted extract were measured out into a 

 small stender dish and submitted to the treatment under consideration 

 for the required time. A check of 2 c. c. was also measured out. In 

 some cases where gases or vapors were used, the stender dish with treated 

 extract was allowed to air for a certain period before the final test with 

 hydrogen peroxide was made. For measuring the amount of oxygen 

 liberated from hydrogen peroxide by the treated portion of the extract 

 and by the check, the apparatus represented in Fig. Ill was used. As 

 has already been explained, this apparatus was in duplicate so that the 

 test with the treated extract could be run in one and the check in the 

 other duplicate. After the stender dish of extract had been introduced 

 into the gas-container, mercury seal was made at the mouth of the 

 container. The mercury manometer was adjusted level, and 

 the reading of the gas-burette taken. Then 5 c. c. of hydrogen peroxid:e 

 were drawn in form burette ''f". As oxygen was liberated and the volume 

 of the gas in the container increased, the mercury in the gas-burette 

 was lowered until the manometer was once more level just at the end 

 of 10 minutes. Then the reading of the gas-burette was again taken. 

 The increase in volume less 5 c. c. (i. e. 5 c. c. of H2O2), represent/ed, the 

 oxygen liberated. Any variation in the volume of oxygen liberated by 

 the treated extract from the volume liberated by the check,, 

 therefore, was due to the influence of the treating agent, since all the 

 other conditions were the ^ame for both extracts. After an extract was 



