CH. VIII.] ESTIMATION OF PEPSIN. 2O5 



tubes 2 to 10 measure I cc. of the hydrochloric acid. Into tubes i 

 and 2 measure i cc. of the gastric juice. Mix the fluid in tube 2 and 

 transfer i cc. to tube 3. Mix this and transfer i cc. of the mixture 

 to tube 4. Proceed in this way till each tube contains i cc: of fluid 

 and each tube contains one-half of the amount of enzyme present 

 in the tube with the next lower number, i cc. of tube 10 being 

 rejected. To each tube add 2 cc. of the edestin solution. Mix and 

 allow the tubes to stand at room temperature (15 to 17 C.) for 30 

 minutes. To each tube add 10 drops of the sodium chloride. The 

 tubes with low numbers are probably clear, whilst the tubes with 

 high numbers are cloudy. Note the tube with the lowest number 

 that shows a cloud. The tube with the number next below it has an 

 amount of gastric juice that just digests 2 cc. of the edestin in 30 

 minutes. Thus the number of cc. of edestin digested by i cc. of 

 gastric juice can be calculated. 



This is best denoted by pe . 



30 



Thus if tube 6 shows a cloud, then in tube 5 (containing i-i6th 

 cc. gastric juice) digestion is complete. Supposing the temperature 



16 2 

 is 16 C., then pe - 7 = ... . = 32. 



30 TS 

 251. The estimation of Pepsin by Mett's method. 



Preparation of the tubes. The whites of several new-laid eggs are beaten 

 to break the membranes, strained through linen or muslin and allowed to 

 stand till free from air bubbles. The liquid is then drawn up into lengths of 

 glass tubing with an internal diameter of between i and 2 mm. Each length 

 is laid flat on a piece of wire gauze, so arranged that it can be dropped into a 

 saucepan of hot water, having a double bottom (" porridge saucepan "). The 

 water in the saucepan is boiled and allowed to stand till that in the inner 

 vessel has cooled to 85 C. The gauze with the prepared tubes is then placed 

 in this inner vessel, and allowed to stand till the water is quite cold. The 

 tubes can be preserved by sealing the ends with shellac. 



Method of estimation . Cut off lengths of 2 cms., breaking the 

 tubes sharply to get an even edge of coagulated egg-white. 



Measure 10 to 20 cc. of the ferment into a small Erlenmeyer 

 flask. In it place two of the tubes of egg-white, shake and cork, 

 and place the flask in a thermostat at 40 C. for 24 hours. The 

 mixture must not be shaken during the digestion. Measure the 

 length of the tube (T) and of the remaining egg-white (W) by means 



