428 



HEPBURN— BIOCHEMICAL STUDIES 



centration of the alkali, the period of time during which it acted, and the 

 temperature at which it acted. Sufficient soUd sodium carbonate was 

 added to the pitcher hquor to bring the salt to the desired concentration. 

 After the resulting solution had been incubated at the desired temperature 

 for the desired period of time, it was neutralized, then acidified with 

 hydrochloric acid, and a digestion experiment was made in the usual way 

 to determine the enzyme activity. The concentration of the sodium 

 carbonate varied between 0.5 and 5 percent; it was permitted to act on 

 the enzyme at a temperature of either 35° to 38° C. or 50° C. for a period 

 of time varying between 30 minutes and 17 hours. Each control experi- 

 ment on untreated liquor was incubated at the same temperature and for 

 the same period of time as its determination proper; then its enzymic 

 activity was determined. 



The typical series of experiments in the following table may be 

 quoted. The substrate in each experiment was 0.01 gram of fibrin. 



"On comparing the results of a, b, and c, it would appear that treat- 

 ment with 1% Na2C03 for one hour at a temperature of 50° C. is an 

 approximate index to the stabiUty of the enzyme. " 



The pitcher liquor lost its acid reaction and its coloration, when 

 passed through a Berkefeldt filter. "It still retains some digestive 

 power, but is far less active than unfiltered liquid, the period of digestion 

 being more than doubled. " Filtration through a Berkefeldt filter caused 

 a marked loss of the enzymic power of solutions of pepsin (from the 

 stomach of the pig) and of salivary ptyalin. Hence the partial loss of 

 proteolytic power by the pitcher Hquor was due to the retention by the 



