GASTRIC ANALYSIS 169 



juice contained inhibiting substances the effect of which is overcome by 

 the dilution recommended. 



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 hi 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 Schutz-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. It is best to allow the 

 egg-white to stand for two or three hours in a vacuum desiccator to more completely 

 remove air. 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 im- 

 mediately 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 Qo -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 



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



