190 BACTEEIOLOGICAL AND ENZYME CHEMISTRY 



The characteristic difference between pepsin and trypsin is 

 that pepsin acts in dilute act'c? solution, and trypsin in dilute alka- 

 line solution. The following experiments may usefully be made 

 to illustrate the characteristic properties of these enzymes. 



A quantity of hard-boiled egg-white may be cut up into 

 strips of approximately 2 cm. x 5 mm. x 1 mm. dimensions 

 and one of these placed in each of eleven test-tubes, to which 

 the following additions are made in order, about 10 c.c. of 

 solution being taken in each case : 



1. Water; 



2. Hydrochloric acid, 1 0*2 per cent. ; 



3. Water -}- J c.c. of ' liquor pepticus ' ; 



4. Hydrochloric acid, 0'2 per cent. -(- J c.c. ' liquor 



pepticus ' ; 



5. Hydrochloric acid, 0*2 per cent. + J c.c. ' liquor 



pepticus ' ; 



6. One per cent, sodium carbonate solution ; 



7. One per cent, sodium carbonate solution -f- J c.c. 



' liquor pepticus ' ; 



8. Hydrochloric acid, 0'2 per cent, -f J c.c. ' liquor pan- 



creaticus ' ; 



9. Water -f J c.c. ' liquor pancreaticus ' ; 



10. Sodium carbonate solution 1 per cent, -f- J c.c. ' liquor 



pancreaticus ' ; 



11. Sodium carbonate solution 1 per cent. + \ c.c. ' liquor 



pancreaticus.' 



All of these are now placed in a water-bath at 40 C., with 

 the exception of numbers 5 and 11, which are boiled. 



At the end of some hours the following results will be 

 observed : the strips of egg-white will be virtually unattacked 

 either by water, by dilute acid or alkali, by pepsin and alkali 

 together, or by trypsin and acid together. On the other hand, 

 some digestion will probably be observed in the case of both 



TT(~n 



1 110 c.c. of made up to 200 c.c. gives a solution of this strength. 



