34 E. S. EDIE 



heated, the lower boihng point of alcohol preventing the alcoholic extract 

 from reaching such a high temperature in the water-bath as the corresponding 

 aqueous extract would reach. No such protection was found to be afforded 

 by alcohol, however. Corresponding aqueous and alcoholic extracts were 

 diluted with alcohol and water respectively so that the percentage of alcohol 

 was the same in both. They were then heated to the same extent and tested 

 on fibrin. 



No. 

 14 



15 



Control 7-9 



These experiments show that the addition of alcohol to an aqueous extract 

 of pancreas does not afford any protection against heat to the trypsin as 

 measured by its action on fibrin. 



In the original experiments on the resistance of trypsin solutions to heat, 

 the solutions, when heated, contained only a very small amount of nitrogen, 

 not more, in some cases, than 0-02 %. The pancreatic extracts used in the 

 experiments now described were very much richer in nitrogen and generally 

 contained 15 to 20 times as much as the older extracts. This corresponds to 

 a considerable amount of protein in the solution and as protein is known to 

 form a loose compound with hydrochloric acid it was decided to try the effect 

 of considerably higher amounts of acid in the solutions to be heated. 



It was now found that the protection afforded to trypsin solutions when 

 heated depends on the amount of acid present, and the more protein there 

 is in solution, the more hydrochloric acid must be added to prevent the trypsin 

 being destroyed by heat. 



The following experiments show this increasing protection with increase 

 of acid: 



(500) 



