ENZYMES AND THEIR ACTION. I/ 



period the tubes are again removed to the bath of ice water in 

 order that the action of the enzyme may be stopped. 



Dilute the contents of each tube, to within about one-half inch 

 of the top, with water, add one drop of a -f$ solution of iodine and 

 shake the tube and contents thoroughly. A series of colors rang- 

 ing from dark blue through bluish-violet and reddish-yellow to 

 yellow, will be formed. 1 The dark blue color shows the presence 

 of unchanged starch, the bluish-violet indicates a mixture of starch 

 and erythrodextrin, whereas the reddish-yellow signifies that eryth- 

 rodextrin and maltose are present, and the yellow solution denotes 

 the complete transformation of starch into maltose. Examine the 

 tubes carefully before a white background and select the last tube 

 in the series which shows the entire absence of all blue color, thus 

 indicating that the starch has been completely transformed into 

 dextrins and sugar. In case of indecision between two tubes, 

 add an extra drop of the iodine solution, and observe them again, 

 after shaking, 



Calculation. The amylolytic activity 2 of a given solution is 

 expressed in terms of the activity of i c.c. of such a solution. For 

 example, if it is found that 0.02 c.c. of an amylolytic solution, 

 acting at 38 C. completely transformed the starch in 5 c.c. of a 

 I per cent starch solution in 30 minutes, the amylolytic activity of 

 such a solution would be expressed as follows : 



This indicates that i c.c. of the solution under examination pos- 

 sesses the power of completely digesting 250 c.c. of a i per cent 

 starch solution in 30 minutes at 38 C. 



2. Quantitative Determination of Peptic Activity, (a) 

 Mett's Method. The determination of the actual rate of peptic ac- 

 tivity is a most important procedure under certain conditions. Sev- 

 eral methods of making this determination are in use. The method 

 of Sprigg 3 ;s probably the most accurate method yet devised for 

 this purpose. It is, however, too complicated and time-consuming 

 for clinical purposes. The method of Mett, given below, is very 

 simple although not strictly accurate. The procedure is as follows : 

 To about 5 c.c. of the gastric juice under examination in a test- 



1 See p. 44. 



2 Designated by " D " the first letter of " diastatic." 



3 Sprigg: Zeitschrift fur physiologische Chemie, 1902, XXXV, p. 465. 



