240 PHYSIOLOGICAL CHEMISTRY 



and centrifugated for a i5-minute period, or longer if necessary, to secure satis- 

 factory sedimentation. At this point, read and record the height of the sediment 

 column. Remove the supernatant liquid by means of a bent pipette, transfer it to 

 a 50 c.c. volumetric flask and dilute it to the 50 c.c. mark with the phosphate- 

 chloride solution. Mix the fecal extract thoroughly by shaking and determine its 

 amylolytic activity. For this purpose a series of six graduated tubes is prepared, 

 containing volumes of the extract ranging from 2.5 c.c. to 0.078 c.c. Each of the 

 intermediate tubes in this series will thus contain one-half as much fluid as the 

 preceding tube. Now make the contents of each tube 2.5 c.c. by means of the 

 phosphate-chloride solution in order to secure a uniform electrolyte concentration. 

 Introduce 5 c.c. of a i per cent soluble starch solution 1 and three drops of toluol 

 into each tube, thoroughly mix the contents by shaking, close the tubes by means 

 of stoppers and place them in an incubator at 38C. for 24 hours. At the end of 

 this time remove the tubes, fill each to within half an inch of the top with ice-water, 

 add i drop of tenth-normal iodin solution, thoroughly mix the contents and examine 

 the tubes carefully with the aid of a strong light. Select the last tube in the series 

 which shows entire absence of blue color, thus indicating that the starch has been 

 completely transformed into dextrin and sugar, and calculate the amylolytic activity 

 on the basis of this dilution. In case of indecision between two tubes, add an extra 

 drop of the iodin solution and observe them again. 2 



The amylolytic value, Df, of a given stool, may be expressed in terms of i c.c. 

 of the sediment obtained by centrifugation as above described. For example, if it 

 is found that 0.31 c.c. of the phosphate-chloride extract of the stool acting at 38C. 

 for 24 hours completely transformed the starch in 5 c.c. of a i per cent starch solu- 

 tion, then we would have the following proportion: ' 



0.31 15 (c.c. starch) :: i(c.c. extract) :X 



The value of X in this case is 16.1, which means that i c.c. of the fecal extract 

 possesses the power of completely digesting 16.1 c.c. of a i per cent starch solution 

 in 24 hours at 38C. 



Inasmuch as stools vary so greatly as to water content, it is essential to an 

 accurate comparison of stools that such comparison be made on the basis of the 

 solid matter. Supposing, for example, that in the above determination we had 

 6.2 c.c. of sediment. Since the supernatant fluid was removed and made up to 



1 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 constant stirring, until it is clear. This ordinarily 

 takes from eight to ten minutes. A slightly opaque solution is thus obtained, which 

 should be cooled and made up to the proper volume before using. 



2 Theoretically we would expect the colors to range from a light yellow to a dark blue, 

 with red tubes holding an intermediate position in the series. This color sequence does 

 often occur, but its occurrence is far from universal. Many times the first tubes in the series, 

 i.e., those containing the largest quantities of the fecal extract, will exhibit a bluish cast of 

 color which should not be confused with the starch color reaction. When these blue tubes 

 are present, they are generally followed by yellow, red and blue tubes in order, the final blue 

 tube, of course, being the regulation starch reaction. Occasionally greenish colors will be 

 obtained to the left of the red color. It also sometimes happens that it is somewhat dif- 

 ficult to determine in which tube to the right of the red color the starch blue color is first de- 

 tected, unless the tube be examined carefully before a strong light. In every instance, how- 

 ever, when these blue and green colors are observed, it is noted that tubes possessing the 

 true dextrin red color are always present between these tubes and the tubes possessing the 

 true starch blue color. It is evident, therefore, that these bluish tints in the tubes to the 

 left of the dextrin color cannot be due to the presence of starch. The cause of the blue color 

 reaction in the first tubes of the series has not been ascertained as yet. 



