:^XPERIMENT STATION BULLETINS. 463 



made to net upon tlie two cntalases separately. The cnide extract was 

 filtered. Then the clear filtrate, containiDg the soluble catalase, was 

 diluted aud treated by the method already described. The residue ou 

 ihe filter was washed as nearly free from the soluble catalase as possible, 

 alter which it was shaken up in a small amount of distilled water. This 

 water containing the insoluble catalase in suspension was then divided 

 into equal samples to be treated as in the other experiments. Charges 

 of hydrocyanic acid gas sufficient to render specimens of P. cornutus 

 lielpless and quiet in 3 to 4 minutes were used. Such a charge of cyanide 

 gas is much stronger than that used in ordinary fumigation. The charges 

 were applied 40 to 45 minutes. (This Avas a longer time than was really 

 necessary to kill specimens of the beetle.) The experiments showed that 

 over 95% of the activity of the soluble catalase and only about 52% of the 

 activity of the insoluble catalase was suspended at the end of a 45-minute 

 period. There was 88% recovery, or more, (after the treated extract 

 stood 15 hours at about 34° F.) in case of the soluble catalase, and 

 about 21% recovery of the activity of the insoluble catalase toward 

 hydrogen peroxide. The insoluble catalase seemed to sliow the greater 

 resistance, but once its activity had been liindered by the poison, great- 

 er permanent injury resulted than in llie similar event with soluble 

 catalase. 



A number of tests were made to determine whether any such recovery 

 of the catalases in an extract would obtain, after treatment with hydro- 

 chloric acid instead of with hydrocyanic acid gas. In preparing a treated 

 extract and its check for this test, when 1 c. c. of ^^^^ acid was added 

 to 2 c. c. of extract, then 1 c. c. of distilled water of the same temperature 

 as the acid was added to the 2 c. c. check extract in order to keep the 

 same dilution in the two portions. The tests Avere run in the apparatus 

 already described. Numbers 22 and 23 in Table V show that j^q^ hydro- 

 chloric acid, was quite destructive to the catalase; and there was no 

 apparent recovery, even upon long standing, if the treated extract and 

 its check were kept at a temperature not far above freezing during the 

 long period of treatment. Upon standing after the first decrease in 

 catalase activity, three cases of increased activit}' for liberating oxygen 

 from hydrogen peroxide did occur in some of the early tests with hy- 

 drochloric acid. However, the increase in these three cases was really 

 brought about by decay which (in a warm room) the weak acid used did 

 not entirely prevent, for long, in the extract. With the precaution of 

 keeping the extracts in the cold (near freezing) during the treatment 

 period, no example of increase in catalase activity at any time after 

 treatment with hydrochloric acid, up to 19 hours, was observed. It 

 may be added that the deleterious action of this acid upon the reducing 

 power of the extract was not so great as it was upon the catalase 

 activit3\ 



The series of tests, results of which are recorded in Table V to show 

 the effect of heat upon the catalases, are for short-interval periods only. 

 Other experiments showed that when the treatment-period was length- 

 ened, temperatures yet lower than 52° C. showed appreciable injury to 

 the catalase activity. For example, at a temperature ranging from 45° 

 to 46° C. for two hours, the ratio of the volume of oxygen liberated in 



