160 Dr. W. Koberts. Estimation of the Amylolytic [May 5 r 



times as great as in those recorded in Set I ; and it is seen that, by 

 using these proportions, the vanishing points and the onset points fell 

 out in nearly the same times in both sets of experiments. 



Mode of Proceeding. — In testing the tryptic activity of a sample of 

 pancreatic extract, the following procedure was adopted: — 50 cub. 

 centims. of fresh milk were diluted with 50 cub. centims. of water, 

 less the quantity of extract intended to be added. The diluted milk 

 was then warmed to 40° C, and maintained exactly at that tempera- 

 ture until the close of the experiment. The intended quantity of the 

 pancreatic extract, say 1 cub. centim., was then added, and the time 

 exactly noted. At the end of each minute a portion of the digesting 

 milk was withdrawn, and boiled for a. few seconds in a test-tube, 

 inclining the test-tube to one side after the boiling in order to observe 

 the effect. The result was at once noted down. As soon as distinct 

 curdling occurred on boiling, the experiment was considered finished ; 

 the time was recorded, and the number of minutes which had elapsed 

 from the commencement of the experiment were reckoned. The result 

 came out in the following form : — 



1 cub. centim. pane, extract + 50 milk=4 minutes at 40° C. 



If no signs of incipient curdling (soiling of the sides of the test- 

 tube) occurred within 3 minutes, a new experiment was made r 

 using, two, three, or four times as much pancreatic extract. If, on 

 the other hand, distinct curdling occurred in 2 minutes, or less, a 

 fresh experiment was made, using half or quarter the quantity of 

 extract. Three or four such experiments usually sufficed to enable 

 the operator to fix the onset point of the reaction somewhere between 

 4 and 6 minutes. 



Mode of Calculating and Expressing the Tryptic Value. — The object 

 of the experiment was to ascertain how many cubic centimetres of milk 

 can be changed to the onset point of the metacasein reaction by 1 cub. 

 centim. of extract in a period of 5 minutes, at the temperature of 

 40° C. The tryptic value, or T, was calculated from the first expres- 

 sion of the results of an experiment in exactly the same way as for 

 diastase. If p be made to signify the quantity of pancreatic extract 

 added to the milk, and m the number of minutes which were required 

 to reach the onset point of the metacasein reaction, then the value of 

 T was obtained by the following formula: — 



p m 



and taking the experiment above given the value of T came oat as; 

 follows : — 



T=--X-=62-5 at 40° C. 

 1 4 



In judging the practical value of this method of trypsimetry, one 

 must have regard to the inherent difficulty of estimating the activity 



