60 



Result. — Two of these groups of tubes failed to catch and were 

 reiuoculated later so that the first group will be considered by itself. 



(1) These 2 tubes were inoculated in the same way from a fluid 

 culture 32 days old. During the first 18 da}' s there was no trace of 

 color or sign of growth in the check tube. On the twenty-seventh 

 day there was a slight growth with feeble yellowing of the surface, but 

 careful scrutin}- was necessary to detect it. On the thirty-fifth day a 

 slight increase of growth was noted. The starch had not dried out 

 much and the whole of it was still bluish white, indicating that there 

 had been no considerable diastasic action. The streak was very thin, 

 very pale 3^ellow, did not hide the substratum, and had no well-defined 

 margins. On the sixty-second day there was decidedly more growth, 

 the whole surface being covered with a thin, distinctly 3'ellow, smooth, 

 homogeneous, wet-shining layer. The body of the starch still pre- 

 served its bluish white luster and retained its water well. The amount 

 of growth in this tube after 62 days was not greater than that present 

 in the other tube at the end of 5 days. In the tube which received 

 the diastase there was, on the fifth day, a distinct but not very copious 

 growth, covering about two-thirds of the slant surface. On the 

 twelfth day there was an abundant bright j'ellow growth covering the 

 whole surface and affording a striking contrast to the check tube. 

 This contrast continued for some time, the difference in the 2 tubes 

 on the fourteenth da}^ being shown in figs. 15 and 16 of the plate 

 accompany ing bulletin 26 of this Division. The color was approxi- 

 mately Ridgway's canary yellow (VI-12). On the twenty-seventh day 

 the slime was still bright yellow, and the amount of growth was esti- 

 mated at 200 times that in the check tube. On the thirty-ninth day 

 there was still no brown stain. 



(2) After 8 days the other 1 tubes were reinoculated copiously over 

 the whole surface with yellow slime taken from the culture just 

 described. They were under the same conditions as to light and tem- 

 perature, the greatest difference between these and the preceding 

 being the enormous number of germs used in making the inoculation. 



Result. — The 2 check tubes behaved alike. On the fourth da}^ there 

 was a trace of 3^ellow growth at the bottom of the slant, but it was 

 feeble, and was visible on not more than one-fiftieth of the whole sur- 

 face. At this time the tubes which received the diastase showed an 

 abundant bright yellow growth over the whole surface, a growth several 

 hundred times as abundant as that in the check tubes. On the sixteenth 

 day, in the check tubes, there was only a feeble growth of 9 or 10 square 

 millimeters. This growth was bright ^'Cllow, but it was not one one- 

 hundredth as much as in the tubes which received the diastase. On the 

 twent3^-seventh da3^, in the check tubes, the growth had doubled, but 

 the substratum was hidden onl}' over a few square millimeters, and the 



