36 E. B. EDIE 



temperatures than is the power to digest caseinogen. It is also seen that the 

 power to digest caseinogen withstands a considerably higher percentage of 

 hydrochloric acid than has generally been supposed, the strength of acid 

 being N/3 in these experiments and several others with similar results. Tn 

 one experiment, after 24 hours at room temperature in N/3 hydrochloric acid, 

 the trypsin still retained about 10 % of its original fibrin digesting power, 

 but otherwise no fibrin was digested at all after treatment of the trypsin 

 with acid of this strength for a day or upwards. 



On the whole, then, treatment of trypsin solutions with hydrochloric acid 

 either at high or low temperatures shows that the power to digest fibrin is 

 more readily destroyed than the power to digest caseinogen. This bears out 

 the theory discussed previously [Edie, 1919] that in some respects the fibrin 

 digesting poAver is the more subject to outside influences and again points 

 to the hydrolysis of fibrin and of caseinogen being carried out by different 

 side chains, those digesting caseinogen being the more stable. 



In my previous paper [1919], the work of Fermi was referred to as showing 

 that after treatment with various reagents trypsin would no longer digest 

 fibrin but w^ould still digest gelatin. Pollak was also mentioned as finding 

 that with different enzyme preparations the relative amounts of serum and 

 gelatin digested varied enormously. I have also found that the relative 

 amounts of fibrin and caseinogen digested by different trypsin solutions vary 

 very much, and this without subjecting the enzyme to treatment of any kind. 



Thus, three enzyme solutions were prepared in exactly the same way, by 

 extracting minced sheep's pancreas with three times its weight of water for 

 14 days and filtering. These were compared at the same time. 1 cc. of each 

 trypsin was taken, with 40 cc. 0-5 % NagCOg and 1 g. fibrin on the one hand, 

 and 1 cc. trypsin with 40 cc. 1-5 % caseinogen in 0-5 % Na2C03 on the other 

 hand. The amounts of digestion in the three cases were as follows: 



The differences in the relative amounts of fibrin and caseinogen digested 

 by these enzymes, especially Nos. 2 and 3, are very marked. Similar results 

 were frequently noticed in other cases, the general rule being that considerable 

 amounts of caseinogen were digested even though a particular enzyme solution 

 had httle or almost no action on fibrin. 



When enzyme solutions were kept for some time it was found that the 

 fibrin digesting power as a rule diminished to a very much greater extent than 

 the caseinogen digesting power. For example, a freshly prepared trypsin, 

 under the usual conditions, digested 16-1 cc. fibrin and 32-9 cc. caseinogen. 

 In 15 months, under the same conditions, this trypsin digested 4-8 cc. fibrin 

 and 18-5 cc. caseinogen. 



(502) 



