LABORATORY AND GREENPIOUSE STUDIES. 73 



that an acid would be formed in the presence of the sugar. The 

 results in growth are as follows: 



After one day at 37° C: Series 1 has all tubes moderately clouded but no gas; series 

 2, same with no change in color of litmus; series 3, has all tubes well clouded and 

 abundant gas production. 



After two days at 37° C: Conditions same in each tube. 



After four days at 37° C: Series 1, all moderately clouded and thin films on surface; 

 no gas formed. Series 2, all moderately clouded with thin film on surface; litmus, 

 shows no signs of reddening nor of bleaching. Series 3, all well clouded with small 

 amount of gas. 



Test for starch in series 1 : Checks with 26, 30, and 41 drops of iodin solution all 

 showed blue-starch reaction. Culture No. 1 showed very transitory blue with 5 and 

 up to 40 drops of iodin; not tested higher. Culture No. 2 with 61 drops produced a 

 dark purple blue, persistent for at least 1 minute. Culture No. 3, up to 20 drops 

 showed no color; 30 and 40 drops caused a slight tinge of purple. Culture No. 4, 

 from 5 to 30 drops caused a very transient blue; 40 drops produced a blue lasting 5 

 seconds. Culture No. 5, 15 drops produced no color whatever; not tested higher. 

 Culture No. 6, from 5 to 30 drops caused a very transient blue; 40 drops produced 

 a blue lasting 5 seconds. Bacillus coli, as high as 40 drops were added without pro- 

 ducing any starch reaction or other color. 



Series 2 was not tested owing to the presence of the litmus. 



Test for starch in series 3: Checks — (a) transient blue with 10, 15, and more drops; 

 (b) same; (c) transient purple with 10 drops; (d) transient blue with 10 and 15 drops; 

 with 20 drops lasts 5 seconds. Culture No. 1 showed transient red purple with 10 

 drops; with 15 drops color lasts 1 minute. Culture No. 2 showed dark purple blue 

 with 24 drops. Culture No. 3 showed transient red purple, same as No. 1. Culture 

 No. 4 showed blue at least 30 seconds with 10 drops; blue black and not purple with 

 15 drops. Culture No. 5 showed bright blue with 10 drops; dense blue black with 15 

 drops. Culture No. 6 showed purple with 15 drops of iodin. Bacillus coli showed 

 purple with 10 drops, lasting slightly longer than with No. 3. 



In series 1 no distinct amylodextrin test was obtained, the occa- 

 sional purple blue being only what may occur in ordinary starch tests. 

 If the iodin solution is added to starch the first reaction is a bright 

 Prussian blue, but this on standing ultimately often becomes purple. 

 The distinct red-purple reaction formed in some of the tests of series 3 

 is the typical reaction and one quite distinctive. This experiment 

 tends to show that the diastase, if it is a diastase that produces the 

 change from starch to amylodextrin, is produced in the presence 

 of a sugar and not in its absence. 



Experiment 4 o.- — Cultures were made on slant potato-starch jelly 

 tubes and incubated at 37° C. In 24 hours coconut cultures Nos. 3 

 and 4 showed good narrow, dry streaks. The other cultures showed 

 no growth. In three days all the tubes but coconut No. 5 showed 

 good growth on the surface of the slant. No 3 was tested with Lugol's 

 iodin solution, but showed no signs of amylodextrin. No. 1 showed 

 a sHght red-purple coloration. None of the other cultures showed 

 any signs of the amylodextrin reaction; aU were bright blue. 



228 



