4 



Scientific Proceedings (117). 



3. By treating solutions of pancreatic extract with colloidal 

 iron and other precipitants such as uranium acetate, alcohol, 

 sodium sulphate and others. Calcium chloride solution in con- 

 centration accomplishes the same result. 



4. The addition of products of peptic digestion, such as those 

 of gliadin or Witte's peptone, to solutions of pancreatic extract 

 also liberate the rennet. 



5. Serum of a rabbit immunized by intravenous injections of 

 pancreatic extracts, when added to solutions of pancreatic ex- 

 tract, liberate the rennet. 



Whatever method of activation is used, in every instance, the 

 rennet itself remains in solution, and some substance is precip- 

 itated, which before precipitation conceals the presence of the 

 rennet. 



I reported some of these results at a Section meeting of the 

 American Chemical Society, held last September, and concluded 

 at the time that the rennet in the pancreatic extract was probably 

 present not as a pro-enzyme, but as an active enzyme mixed with 

 substances which are antagonistic to its action. The conclusion 

 is based on the foregoing experiments, the most significant of 

 which is the one showing the effect of immunized serum on in- 

 active pancreatic extract. Apparently the inactive solution of 

 pancreatic extract is capable of producing in an immunized animal 

 an antibody for the substance in the pancreatic extract, which is 

 antagonistic to the rennet. The antibody thus produced is in 

 the nature of a precipitin. The lack of any specific method of 

 activation seemed to support this view that there is no pro-ferment. 

 However, the proof is indirect, hence not final. Various attempts 

 to recover the antagonistic substance in active form proved futile. 

 The most that can be said about it is that it probably is a substance 

 of protein nature which coagulates at a temperature between 60 

 and 65 0 C, is precipitable by sodium sulphate and other precip- 

 itants, and is capable of producing a precipitin in immunized 

 serum. 



These facts brought to mind the former controversy concerning 

 the nature or state of the rennet in gastric mucosa. 



You will recall that rennet is believed to exist in two states, 

 that of an active enzyme (or rennet) and as a pro-enzyme (or 



