68 



stratum, but no brown stain, no decided smell, and no ocular evidence 

 of any diastasic action. The germs were carefully scraped off and 

 iodine water poured into the tube, whereupon there was an immediate 

 and general blue reaction, showing that very little of the starch had 

 been changed. This shows clearly that increased growth does not 

 necessarily imply an}' increased secretion of the diastasic ferment. 

 The check tube could not be compared owing to a contamination. 



(4) A few days later another check tube was inoculated and a similar 

 feeble growth ensued. A tube containing 500 milligrams of dextrin, 

 which was inoculated for comparison, gave a much better growth. On 

 the third day the whole surface of the slant in this tube was covered 

 bj" a thin, distinctly j^ellow, dr}^ layer, and there was no visible dia- 

 stasic action. On the twelfth day the growth was smooth, Avet-shining, 

 bright yellow, and about S times as abundant as in the check tube. 

 There was also a decided diastasic action, involving the outer 5 milli- 

 meters of the starch. This result contradicts the preceding experiment 

 with dextrin and is probabl}^ attributable to the action of some unde- 

 tected, intruding organism (see p. 64). 



Nutrient Starch Jelly No. 2. 



The nutrient solution used in preparing this medium differed from 

 the preceding by addition of sodium sulphate; by a considerable reduc- 

 tion of the magnesium sulphate and calcium chlorid; b}- a slight 

 reduction of the sodium chlorid, sodium asparaginate, and ammonium 

 lactate, and by a slight increase of the dipotassium phosphate (for 

 exact composition see loco clt.). Each tube received exactly 10 c. c. 

 of this solution and 2 grams of dry potato starch free from an}^ trace 

 of sugar. For comparison a culture was laid at the same time on 

 starch jelly No. 1, containing 2 grams of the same starch and 10 c. c. 

 of the glycerin-free Uschinsky. The slant surface of each substratum 

 was inoculated in the same way, carefully and very copiously, with 

 bright yelloAv slime from a starch-jell}^ culture IT days old. The tubes 

 were kept in a dark place at room temperatures ranging from 21° to 

 31° C. (most of the time below 28°). 



Result. — On the fifth day there was a feeble, bright yellow growth, 

 much alike in each tube, and no visible diastasic action. On the elev- 

 enth day there was a thin, bright yellow growth over nearly the whole 

 surface — i. e., a considerable increase of growth, but still no diastasic 

 action. Both tubes were much alike, but there appeared to be slightly 

 moi-(^ gi-owth in starch jelly No. 1. On the twenty-fourth day the 

 growth in starch jelly No. 2 had increased but little. This growth 

 was wet-shining and distinctly yellow, but so feeble that the substratum 

 was not hidden; there was no brown stain in the substratum, and no 

 visible dia.,tasic action. In starch icily No, 1 there was distinctly 

 more growth, but no visible diastasic action. An intruding colony 



