68 



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

 of an}^ diastasic action. The germs were carefully scraped oti' and 

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

 and general l)lue reaction, showing that ver^- 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 tu))e could not ))e compared owing to a contamination. 



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

 feeble growth ensued. A tu})e containing 500 milligrams of cU^xtrin, 

 which was inoculated for comparison, gave a much ))etter gi-owth. On 

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

 by a thin, distinctly yellow, dr}^ hiyer, and there was no visible dia- 

 stasic action. On the twelfth da}' the grow^th was smooth, wet-shining, 

 bright yellow, and about S times as abundant [is 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 probably attributable to the action of some unde- 

 tected, intruding organism (see p. 64). 



NuTKiKNT Starch Jklly No. 2. 



The nutrient solution used in preparing this medium differed from 

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

 tion of the magnesium sulphate and calcium chlorid; by a slight 

 reduction of the sodium chlorid, sodium asparaginate, and anmionium 

 lactate, and b}' a slight increase of the dipotassium phosphate (for 

 exact composition see loco cit.). Each tube received exactl}^ 10 c. c. 

 of this solution and 2 grams of dry potato starch free from any 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 gh'Cerin-free Uschinsky. The slant surface of each substratum 

 was inoculated in the same way, careful!}^ and very copiousl}', with 

 })right yellow slime from a starch-jell}^ culture 17 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 considera])le increase of growth, but still no diastasic 

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

 more growth 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 fee})le that the sul)stratum 

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

 visible diaotasic action. In starch jelly No. 1 there was distinctly 

 more growth, i)ut no visible diastasic action. An intruding colony 



