40 E. S. EDIE 



power being practically the same as at first and there was no evidence whatever 

 in support of the view that with extracts a few hours old coagulation really 

 takes place but the clot is redissolved almost instantly. These last experiments 

 once more show that pancreatic extracts differ greatly in their milk coagulating 

 and proteolytic powers. This again points to there being either two or more 

 separate enzymes present, which develop at very different rates from their 

 zymogens, or at least the groups which are responsible for the different 

 functions develop their properties quite independently. 



Summary. 



1 . The amount of acid required in order to protect trypsin from destruc- 

 tion by heat depends on the amount of protein present. The more protein 

 in solution, the more acid required. If not enough acid is present to afford 

 complete protection to the trypsin, the fibrin digesting power is usually 

 destroyed by heat to a considerably greater extent than the power to digest 

 caseinogen. 



2. Hydrochloric acid at moderate temperatures also destroys the fibrin 

 digesting power considerably more rapidly than the caseinogen digesting 

 power. 



3. The relative amounts of fibrin and caseinogen digested vary very 

 much in different pancreatic extracts. 



4. The milk coagulating power of pancreatic extracts is more easily 

 destroyed by heat than the proteolytic power. 



5. Generally, but not always, freshly prepared pancreatic extracts have 

 no milk coagulating power. These extracts are always actively proteolytic, but 

 the proteolytic power does not fall off so rapidly as to justify the assumption 

 that the non-appearance of a coagulum with milk is due to the coagulum 

 being really formed but instantly redissolved. All these facts point to the 

 proteolytic and milk coagulating powers of pancreatic extracts being due to 

 a number of distinct enzymes, or, if only one enzyme is concerned, to the 

 different functions being due to different groups of the molecule. 



REFERENCES. 



Edie (1914). Biochem. J. 8, 84. 



(1919). Biochem. J. 13, 219. 



Edkins (1891). J. Physiol. 12, 193. 

 Halliburton and Brodie (1896). J. Physiol. 20, 101. 

 Lcnard (1914). Biochem. Zeitsch. 60, 43. 

 MeUanby and WooUey (1913). J. Physiol. 47, 339, 



(1914). J. Physiol. 48, 287. 



Vernon (1901). J. Physiol. 27, 174. 



(1903). J. Physiol. 29, 302. 



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