FERMENTATION 245 



at room temperature for many months. It is 

 rapidly destroyed at SS'-^C. 1 



Conversion of Trypsinogen to Trypsin by En- 

 terokinaae. Place 5 c.c. of 0.25 per cent solution 

 of sodium carbonate in each of two test-tubes 

 A and B, containing gelatine prepared by Fermi's 2 

 method. To A add a few drops of pure pancreatic 

 juice ; 3 to B add the same quantity of pure pan- 

 creatic juice and a few drops of enterokinase. 

 Place at a temperature of 30-35 C. The pure 

 juice will not act on it, but the juice to which 

 enterokinase was added will dissolve the gelatine. 

 In order to determine accurately the amount of 

 gelatine dissolved, the tubes often must be cooled 

 to 10 C. 



ABSORPTION OF PROTEIDS 



Diffusion of Proteids through Dead Membrane. 



Bend a cylinder of parchment paper and fasten 

 the ends to a glass rod. Place in the parchment 

 tubes thus formed 25 c.c. of each of the follow- 



1 BAYLISS and STARLING: Journal of Physiology, 1903, 

 xxx, p. 80. 



2 FERMI and REPETTO : Centralblatt fur Bakteriologie und 

 Parasitenkunde, 1902, xxxi, p. 404. Narrow glass tubes, pref- 

 erably graduated, are tilled one half full of gelatine (5 to 10 

 per cent) containing one per cent of sodium fluoride. 



8 Obtained by catheterizing the pancreatic duct of the rabbit 

 (Rachford's method), Journal of Physiology, 1891, xii, p. 81. 



