REVERSION OF HYDROLYSIS 433 



(a) 10 cc. of unconcentrated products + 0.5 cc. of 15 per cent pepsin. 



(6) 10 cc. of unconcentrated products + 1.0 cc. of 15 per cent pepsin. 



(c) 10 cc. of unconcentrated products + 1.5 cc. of 15 per cent pepsin. 



(d) 10 cc. of unconcentrated products + 2.0 cc. of 15 per cent pepsin. 



(e) 10 cc. of unconcentrated products + 3.0 cc. of 15 per cent pepsin. 



The one set was kept at 65 degrees, while the other was kept 

 at 36 degrees, both in tightly stoppered vessels containing excess 

 of toluol. After 24 hours there was no sign of any precipitate 

 or opalescence in the mixtures which had been kept at 36 degrees, 

 while in the duplicate set, which had been kept at 65 degrees, 

 (e) contained a heavy precipitate which left the supernatant 

 fluid clear, (c) and (d) contained, also, heavy precipitates which, 

 however, left the supernatant fluid strongly opalescent, and (a) 

 and (b) both contained slight precipitates. After 24 hours more, 

 no change had occurred in any of the solutions and those which 

 had been kept at 65 degrees were now returned to 36 degrees. 

 After a lapse of three weeks no trace of precipitate had appeared 

 in any of those solutions which had been at 36 degrees throughout, 

 while no further change had occurred in those which had been 

 kept at 65 degrees for 48 hours. 



The probable identity of the precipitate which is thus pro- 

 duced, with that which is produced by the action of pepsin upon 

 the concentrated (=6 times) products at 36 degrees was shown 

 by the following experiments. 



Thirty cubic centimeters of 15 per cent pepsin (Gruebler's 

 puriss. sice.) were added to 150 cc. of the unconcentrated prod- 

 ucts of the complete peptic hydrolysis of JV/50 sodium caseinate 

 and the mixture was kept at 65 degrees for 48 hours in the 

 presence of excess of toluol. The resulting precipitate was col- 

 lected on a hardened filter paper and washed with distilled water 

 until the washings were colorless; it was then dissolved by allow- 

 ing dilute sodium hydrate to pass through the filter and repre- 

 cipitated by allowing this filtrate to pass into a beaker contain- 

 ing excess of dilute acetic acid. The precipitate thus obtained 

 was collected on a hardened filter paper, washed with large 

 volumes of water, alcohol, and ether and dried over CaCk and 

 later over H 2 S0 4 . The product was a greyish-white, friable 

 hygroscopic powder resembling in its physical properties and 

 precipitation-reactions "paranuclein A" It was analysed for 

 phosphorus by Neumann's method and found to contain 1.65 



