ACTION OF THE ENZYMES. 131 



Glass tubes 1 to 2 mm. in diameter are drawn full of fresh 

 white of egg and dipped for exactly a minute into water 

 having a temperature of 95 C., in which the albumin coagu- 

 lates. After the tube has been allowed to cool slowly it is 

 cut into short pieces and these are dropped into the digestion 

 mixtures to be studied. The number of millimeters of egg- 

 white digested out of the tube is determined by the help 

 of a low-power microscope and scale from which the digestive 

 power of one mixture as compared with that of another may 

 be determined. According to a principle first declared by 

 SCHUTZ the amount of proteolytic ferment present in the 

 various reaction mixtures is proportional not to the number 

 of millimeters of albumin digested out of the tubes but to 

 their square. A digestion mixture which dissolves 2 mm. of 

 albumin out of a tube is supposed to contain not twice as much 

 proteolytic ferment as one which digests only 1 mm. out of 

 a tube, but four times as much. 



METT'S method, though exceedingly simple, is by no means 

 free from error. 



(c) Spriggs' Method. SPRIGGS 1 has devised a method for 

 determining quantitatively the rate at which a coagulable 

 protein is digested under the influence of different proteolytic 

 ferments which for simplicity and accuracy is far superior 

 to the ordinary methods employed for this purpose. SPRIGGS' 

 method takes advantage of a physical change a decrease in 

 viscosity which occurs in a protein solution when this is acted 

 upon by a proteolytic ferment. In order to measure this 

 change in viscosity use is made of the viscosimeter of OSTWALD^ 

 illustrated in Fig. 19a, which allows an experimenter to deter- 

 mine accurately the time required for a measured amount 

 of liquid contained in A to flow through the capillary tube 

 B into C. The greater the viscosity, the greater, of course, 

 will be the time required for a liquid to flow through the 

 capillary tube. 



1 SPRIGGS: Zeitschr. f. physiol. Chem., 1902, XXXV, p. 465. 



