24 BULLETIN 433, U. S. DEPAETMENT OP AGRICULTtTE:fi. 



forms, since there is a gradual increase in the total soluble protein 

 during the experiment (except in the case of the samples incubated 

 7, 14, and 21 days), whereas the comparisons are based upon the 

 amount of coagulable protein present in the fresh material. The 

 data under the heading " Noncoagulable nitrogen " show more clearly 

 the true extent of the transformation of coagulable protein into non- 

 coagulable forms. 



The change of coagulable protein into noncoagulable forms may 

 be ascribed to the action of the enzym protease, which also acts upon 

 the insoluble muscle proteins. 



Noncoagulable nitrogen. — There is a practically continuous in- 

 crease in the noncoagulable nitrogen throughout the course of the 

 experiment; the entire increase amounting to 173.82 per cent, as com- 

 pared with a decrease of 80.24 per cent in the coagulable nitrogen 

 during the same period. 



Proteose nitrogen. — The most rapid increase in this constituent 

 occurs during the first seven days of the experiment, though there 

 are some greater increases after that time. The sample incubated 

 for 100 days contains only slightly more proteose nitrogen than the 

 sample incubated for 7 days, and not as much as several of the 

 samples incubated for intermediate periods. These data indicate, in 

 conformity with the well-known fact that proteoses are simply inter- 

 mediate products in the autolysis of muscle proteins, that there is 

 no appreciable accumulation of proteose nitrogen during autolysis. 

 It is very apparent that the amount of proteoses in muscular tissue 

 is not a true measure of protein autolysis. 



In the light of present information, proteoses may be regarded as 

 a product of the action of the enzym protease upon muscle proteins. 



Amino nitrogen. — The changes in amino nitrogen effected by the 

 autolysis are very interesting in that each change is in the nature of 

 a pronounced increase, and thatfeach successive increase is larger than 

 its predecessor, until, in the sample that was incubated for 100 days, 

 the amount of amino nitrogen is more than eight times as large as 

 that in the nonincubated sample. In a general way, the rate of in- 

 crease diminishes as the incubation period is lengthened, since more 

 than one-half of the total increase occurs during the first 28 days of 

 autolysis. 



The increases in amino nitrogen represent an accumulation of the 

 end products of proteolysis, and furnish an excellent index of the 

 extent of protein autolysis. They are produced by the combined 

 action of various proteolytic enzyms — protease and erepsin in par- 

 ticular — upon the muscle proteins and their cleavage products. 



Ammoniacal nitrogen. — The data show an almost continuous in- 

 crease in this constituent during the entire experiment. In general, 

 the increases in ammoniacal nitrogen follow those in amino nitrogen, 



