1 66 PHYSIOLOGICAL CHEMISTRY 



Procedure. Introduce into a small Erlenmeyer flask i c.c. of gastric juice 

 and 15 c.c. of N/2O HC1 ( = 0.18 per cent HC1). Add two Mett tubes prepared 

 as indicated below, stopper the flask to prevent evaporation and place in an in- 

 cubator at 37C. for 24 hours. By means of a low power microscope and a milli- 

 meter scale (graduated to half millimeters) determine accurately the length of 

 the column of albumin digested at each end of the tubes. It is well to run the 

 determination in duplicate in which case the result is the average of the eight 

 figures obtained. Ordinarily from 2-4 mm. of albumin are digested by normal 

 human gastric juice. 



Calculation. The peptic power is expressed as the square of the number of 

 millimeters of albumin digested. This is based on the Schiitz-Borissow law that 

 the amount of proteolytic enzyme present in a digestion mixture is proportional 

 to the square of the number of millimeters of albumin digested. Therefore a 

 gastric juice which digests 2 mm. of albumin contains four times as much pepsin 

 as one which digests only i mm. of albumin. 



Example. If the microscopic reading gives on an average 2.2 mm. of albumin 

 digested the pepsin value for the diluted juice would be 2.2 2 = 4.84, and for the 

 pure undiluted juice, 4.84X16 = 77.44. 



Preparation of Mett Tubes (Christiansen's Method). 1 The liquid portions of 

 the whites of several eggs are mixed and strained through cheese cloth. The mix- 

 ture should be homogeneous and free from air bubbles. A number of thin-walled 

 glass tubes of 1-2 mm. internal diameter are thoroughly cleaned and dried and cut 

 into lengths of about 10 inches. These are sucked full of the egg-white and kept 

 in a horizontal position. Into a large evaporating dish or basin 5-10 liters of water 

 are introduced and heated to boiling. The vessel is then removed from the fire 

 and stirred with a thermometer until the temperature sinks to exactly 85C. The 

 tubes filled with egg-white are immediately introduced and left in the water until 

 it has cooled. The tubes thus prepared are soft boiled, more easily digested than 

 hard boiled tubes, and free from air bubbles. The ends are sealed by dipping in 

 melted paraffin or sealing wax (preferably the latter), and the tubes can be kept thus 

 for a long time. When ready for use mark with a file and break into pieces about 

 % inch long. After cutting, the tubes should be immediately introduced into the 

 digestion mixture or may be kept a short time under water. Tubes whose ends are 

 not squarely broken off must be rejected. 



The digestibility of different egg-whites varies widely. Hence in making up 

 a new set of tubes if we wish our results to be comparable these tubes must be 

 standardized against those first prepared. This may be done by running simul- 

 taneous tests with tubes from the two series, using the same gastric juice and com- 

 paring the lengths of the columns digested in each case. Christiansen's method of 

 preparing tubes of the same digestibility is to be preferred. He proceeds as in 

 the original preparation of the tubes except that as the water cools from 9o-8oC. 

 a single tube containing the new egg-white is dropped in at each degree change of 

 temperature, that is at 90, 89, etc. Pieces of each of these tubes as well as of the 

 original standard tubes are then allowed to digest simultaneously in portions of the 

 same gastric juice. One of these tubes should show a digestibility equal to that 

 of the standard tubes. For example the tube coagulated at 88C. may show the 

 proper digestibility. Then the new series of tubes should be made in the same man- 

 ner as this one, that is introduced at 88C. The tubes thus prepared should be 

 again checked up with the standard to see that no mistake has been made. 

 1 Christiansen: Biochem. Zeit., 46, 257, 1912. 



