116 



HEPBURN— BIOCHEMICAL STUDIES OF 



In the first series of experiments, reported in detail in Table I.. 

 the pitcher liquor was permitted to act on a given substrate for the 

 time stated. Undissolved protein was then removed by filtration, 

 and was washed on the filter ; the combined filtrate and wash- 

 ings were made neutral in reaction. Any precipitated metaprotein 

 was separated by filtration, and was washed on the filter ; the com- 

 bined filtrate and washings were neutralized, if necessary. One 

 half their volume of a neutral, 40 per cent, formaldehyde solution 

 was then added, and the carboxyl groups of the amino acids were 

 immediately titrated with standard sodium hydroxide solution. It 

 should be noted that no acid was added in the digestion experiments 

 of Table I. 



A second series of experiments was carried out with edestan as 

 the substrate ; in these experiments, the hydrochloric acid, which 

 was used to convert edestin into edestan, was present in the solu- 

 tion during the digestion. The details are given in Table II. 



TABLE IL 



FoRMOL-TlTRATION AFTER DIGESTION OF EdESTAN. 



In both series of experiments the liquor from j-/;7;nr/aYcd pitchers 

 invariably digested the substrate, liberating compounds which were 

 of the nature of amino acids, and responded to the formol-titration. 

 The liquor from non-stimulated pitchers did not digest the substrate 

 with the production of such compounds, for the formol-titration 

 invariably was zero. 



Digestion of Carmine Fibrin. 



Two sets of experiments were made using carmine fibrin as the 

 substrate. In both series, the temperature of incubation was that 

 of the room. The liquor from a separate pitcher was used in each 



