38 E. S. EDIE 



From these two experiments it will be seen that though the heated trypsin 

 is still able to digest a considerable amount of fibrin, its milk coagulating 

 power, if any, is now quite negligible. 



27, 20 cc. trypsin + 0-5 cc. N HCl. Half kept at 100° for 1 minute and filtered. 



(a) 1 cc. trypsin, 20 cc. milk. Digestion 39*3 cc. 



(6) 1 cc. trypsin (heated), 20 cc. milk. Digestion 4-6 cc. 



Digestion 1 hour. Tannic acid added and digestion estimated as in the usual caseinogen 



experiments. 



(1) 20 cc. milk, 1 cc. fresh trypsin. Complete coagulation in 5 minutes. 



(2) 20 cc. milk, 1 cc. heated trypsin. No coagulation in 2 hours. 



28. Similar to last experiment. 



(a) 1 cc. trypsin, 20 cc. milk. Digestion 38-4 cc. - 



(b) 1 cc. trypsin (heated), 20 cc. milk. Digestion 3-9 cc. 



(1) 20 cc. milk, 1 cc. fresh trypsin. Complete coagulation in 5 minutes. 



(2) 20 cc. milk, 1 cc. heated trypsin. No coagulation in 2 hours. 



These two experiments confirm Nos. 25 and 26 in showing that the milk 

 coagulating power of pancreatic extracts is more readily destroyed by heat 

 than the proteolytic power. 



It was noticed that the coagulated casein gradually dissolved under the 

 influence of the fresh trypsin, digestion of this protein taking place rapidly 

 even in neutral solution. 



More striking differences are found between the milk coagulating power 

 and the proteolytic action of pancreatic extracts under certain conditions 

 without subjecting these to any such drastic treatment as heating to 100° 

 involves. Edkins [1891] found that fresh, active pancreatic extracts were not 

 so active in altering milk so as to produce Roberts' "metacasein" reaction 

 as were older extracts, but that the proteolytic action was greater in the fresh 

 extracts. Edkins suggested that the production of the metacasein reaction 

 might be an aspect of the proteolytic enzyme of the pancreas. Halliburton 

 and Brodie [1896] confirmed what had been pointed out by Benger, that 

 freshly prepared extract of pig's pancreas had very Httle curdhng action on 

 milk, but acquired this property on being kept a considerable time. They 

 accounted for this fact by supposing that the trypsin at first masks or hinders 

 the milk curdhng enzyme, but that the former enzyme deteriorates more 

 quickly and so finally allows the rennin to reveal its presence. Vernon [1901] 

 obtained similar results and found that the ratio of rennin value to tryptic 

 value varied largely in different extracts of pancreas and also in the same 

 extracts at different times. In alcohohc extracts the ratio usually became 

 higher as the extract became older, the tryptic value deteriorating more 

 rapidly than the rennin. In glycerol extracts, however, the ratio diminished 

 after say nine weeks, owing to the trypsin being liberated more slowly from 

 its zymogen than the rennin. Some glycerol extracts which were very rich 

 in trypsin gave practically no clot at all, as though the clot were dissolved 

 nearly as fast as it was formed. In a later paper, Vernon [1903] found that 

 rennin and trypsin were precipitated from pancreatic extracts to practically 



(504) 



