196 PHYSIOLOGICAL CHEMISTRY 



solution of soluble starch 1 and place each tube at once hi a bath of ice-water. 2 

 When all the tubes have been prepared in this way and placed in the ice-water 

 bath they are transferred to a water-bath or incubator and kept at 38C. for from 

 30 minutes to an hour. 3 At the end of this digestion 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 1/2 inch of the top, with 

 water, add one drop of a N/io solution of iodine and shake the tube and contents 

 thoroughly. A series of colors ranging from dark blue through bluish violet and 

 reddish yellow to yellow, will be formed. 4 The dark blue color shows the presence 

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

 dextrin, whereas the reddish-yellow signifies that erythrodextrin 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 5 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 38C., 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 : 



rC=2so 



This indicates that i c.c. of the solution under examination possesses the power 

 of completely digesting 250 c.c. of i per cent starch solution in 30 minutes at 

 38C. 



Wohlgemuth has suggested a slight alteration in the above procedure for use 

 in the determination of tne amylase content of thejfeces. 6 A modification of the 

 Wohlgemuth procedure 7 for this purpose is given in the chapter on Feces. 



EXPERIMENTS ON PANCREATIC LIPASE 



i . Influence of Bile on Action of Lipase. Prepare five test-tubes as follows : 

 (a) 5 c.c. neutral pancreatic extract -f 0.5 c.c. olive oil -f 4.5 c.c. water. 



1 Kahlbaum's soluble starch is satisfactory. In preparing the i per cent solution, the 

 weighed starch powder should be dissolved in cold distilled water in a casserole and stirred 

 until a homogeneous suspension is obtained. The mixture should then be heated, with con- 

 stant stirring, until it is clear. This ordinarily takes about 8-10 minutes. A slightly 

 opaque solution is thus obtained which should be cooled and made up to the proper volume 

 before using. 



2 Ordinarily a series of six tubes is satisfactory, the volumes of the enzyme solution used 

 ranging from * c.c. to o.i c.c. and the measurements being made by means of a i c.c. gradu- 

 ated pipette. All tubes should contain the same volume of material. To accomplish 

 this add appropriate amounts of distilled water to tubes receiving less than i c.c. of enzyme 

 solution. Each tube should be placed in the ice-water bath as soon as the starch solution 

 is introduced. It will be found convenient to use a small wire basket to hold the tubes. 



3 Longer digestion periods may be used where it is deemed advisable. If exceedingly 

 weak solutions are being investigated, it may be most satisfactory to permit the digestion to 

 extend over a period of 24 hours. 



4 See p. 55. 



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



8 Wohlgemuth: Berliner klinische Wochenschrift, 47, 92, 1910. 



7 Hawk: Archives of Internal Medicine, 8, 552, 1911. 



