18 



(4) A portion of the solution was neutralized. Heating 

 failed to produce a precipitate in it. 



(5) The same negative result (4) was obtained with the 

 alkalized solution. 



(6) After diluting the original solution, no precipitate was 

 formed on heating. 



(7) A bulky white flocculent precipitate was formed when 

 the solution was added to alcohol (sulphates?). A solution 

 of this precipitate gave no precipitate on heating. 



The elastose-like precipitation that ensued on heating the 

 acid solution (2, 3) led to the conclusion that possibly the 

 result was due to a constituent of the pepsin. Accordingly, 

 a solution was made of pepsin in 0.2 per cent. HC1 and, 

 on heating, a faint clouding of the solution took place, but 

 without further change on boiling or on subsequent cooling. 



Saturation of this peptic solution with (NH 4 ) 2 SO 4 failed to 

 yield an appreciable precipitate. 



b. Pure osseoalbumoid was treated with i liter of 0.2 per 

 cent. HC1 containing 0.5 gram of pepsin (P. D. & Co. i : 4000) 

 and placed in an incubator at 35 C. at 11.05 A - M - 



11.45 Most of the material had disappeared into solution. 

 Some of the liquid was withdrawn and, on adding (NH 4 ) 2 SO 4 

 with very little heating, a dark substance was precipitated, 

 which proved to be insoluble in water, and was returned to 

 the digestive mixture. 



12.00 About 15 cc. of the fluid were withdrawn, filtered, 

 and the filtrate saturated with (NH 4 ) 2 SO 4 in the cold. A 

 white flaky material was precipitated, which was readily soluble 

 in water, but on heating this solution no precipitate was 

 formed. 



A sample of the pure pepsin-acid solution, which was used 

 in the foregoing experiment, was saturated with (NH 4 ) 2 SO 4 . 

 A very slight amount of precipitate was formed which dis- 

 solved in water but gave no precipitate on heating. 



The remainder of the solution of the (NH 4 ) 2 SO 4 precipitate 

 was dialyzed till free from sulphate and then evaporated to 

 dryness on a water bath at 40 C. The dialyzate contained 



