61 



ratio of growth in the 2 sets of tubes was still about tlie same, viz, 

 1 : 100. The starch was still bluish white. On the twenty-seventh day, 

 in the tubes which received the diastase, the growth covered the whole 

 surface of the slant (800 to 900 sq. mm.) with a smooth, homogeneous, 

 wet-shining, canary yellow layer, which was abundant enough to hide 

 the substratum. There was a trace of pink in the starch, but no brown 

 stain. On the thirty -fifth day the starch jelly was removed from one 

 of the check tubes. It was as firm and elastic as when first prepared. 

 On breaking it into fragments and throwing it into boiling Soxhlet's 

 solution (5 c. c. standard CuSO^ 5 H^O solution; 5 c. c. standard alkaline 

 solution; 40 c. c. distilled water) and continuing the boiling 3 minutes, 

 the fluid was as blue as at the beginning, and the only precipitate of 

 copper oxide was an extremely slight one restricted to those fragments 

 of the jelly which were immediately under the bacterial layer. Cer- 

 tainly not more than one one-thousandth of the starch was converted. 



(3) The experiment just described was repeated 3 months later in 

 the warmer weather of midsummer. A new stock of the medium 

 was prepared and in this case each tube received 2 gr. of the dry 

 potato starch and 8 c. c. of the nutrient mineral solution. Instead, 

 however, of converting the starch with diastase, the carbon food was 

 supplied by the addition of various sugars, alcohols, and gums. 

 No mention will be made here of anything but the check tube 

 and a tube of the same stock fortified by the addition of 500 mg. of 

 a dextrine, which contained a substance reducing Soxhlet's solution 

 but no amylodextrine and no substance reducing Barfoed's reagent. 

 Both tubes were inoculated at the same time and in the same way; i.e., 

 each with a large loop of yellow slime from a fructose-agar culture 

 17 days old, but still in excellent condition owing to its having grown 

 slowly on the start. The tubes were kept in a dark closet at room 

 temperatures ranging from 25° to 32° C. (30° to 32° during the first 

 5 days). Tubes of Ps. campestris and Ps. ■phaseoU were also inocu- 

 lated at the same time and kept under the same conditions. 



Result. — In the check tube of Ps. hyaclnthi there was no visible 

 growth during the first 18 hours. On the third day there was a very 

 slight growth (barely visible), and the bluish white translucent appear- 

 ance of the starch remained unchanged. In the tube which received 

 the dextrine, growth was visible in 18 hours, ))ut it was still feeble on 

 the third day; i. e., growth was retarded. On the third day, in the 

 check tubes of Px. campeHtrk and T^s-. phaseoll, there was 20 times as 

 much growth, and the starch jelly under the slime, to a depth of 2 

 mm., was changed to a dead, opaque white. Returning to the hya- 

 cinth germ, there was on the seventh day, in the check tube, a very 

 thin, pale yellow streak or film down the middle of the slant. In the 

 tube which received the dextrine the whole surface was covered by a 



