92 PHYSIOLOGY OF ALIMENTATION. 



is added 0.1 c.c. of the extract prepared above. In one 

 minute the glycogen solution has lost its color, and the TROMMER 

 test results positively. The paste from which the extract has 

 been obtained fails to remove the color from a similarly pre- 

 pared mixture of glycogen and iodine, even when several 

 minutes are allowed. 



(/?) By methods similar to those described above, 60 c.c. 

 of juice are obtained from"59.4 grams of dogs' pancreas. The 

 extract has been kept for five days under toluol. When 2 c.c. 

 of this extract are mixed at room temperature with 1 c.c. of 

 a two-percent glycogen solution, and to this is added as 

 quickly as possible a KI-I solution, no change in color is ob- 

 tained, indicating that the glycogen has been changed into 

 sugar even in these few seconds. Even when 3 c.c. of the 

 glycogen solution are added to the extract, the decomposition 

 of the glycogen occurs so quickly that a reaction with iodine 

 cannot be obtained. Not until 3 c.c. of the extract are mixed 

 with 25 c.c. of the glycogen solution (J gram dry glycogen) is 

 this possible. After this mixture has been kept in the incu- 

 bator at 37 C. for one-half hour, it, too, no longer gives a 

 positive iodine reaction. On the following day 0.5 c.c. of the 

 extract is mixed with 5 c.c. of the glycogen solution. After 

 standing for eight minutes at room temperature the mixture 

 has lost its color. The TROMMER test is positive. Examina- 

 tion of the paste from which the extract has been obtained 

 shows it to be unable to act upon the glycogen. 



(/) It seems to be true of a number of the ferments found 

 in cells and in their secretions that these ferments do not 

 exist as such in them, but in an inactive form known as 

 proferments or zymogens. The most striking example of such 

 a zymogen is probably the entirely inactive proferment of 

 trypsin (trypsinogen, as it is sometimes called), found in the 

 pancreatic juice. This proferment (as present in the pan- 

 creatic juice obtained directly from the pancreatic duct) is 

 not able to act upon proteins until it has been converted 

 into trypsin (alkali-proteinase) by coming in contact with a 

 substance contained in the secretions of the small intestine 

 (enterokinase). ^The proferment of alkali-proteinase is found 

 also in the body of the pancreas, and this fact has been con- 



