I 



58 



with about 1 c. c. of distilled water containing the commercial Taka- 

 diastase. Each tube received 2u milligTams of this diastase, which was 

 allowed to act 4|^ hours at '2o^ C. and then destroyed by steam heat. 

 These tubes were then inoculated from three different cultures of Ps. 

 lajaernthi. a beef-broth culture li days old. a turnip culture 9 days 

 old. and a carrot culture 9 days old. The fluid loops were streaked: 

 the solid loops were rubbed carefully over the whole slant. The tubes 

 were then kept in the dark at room temperatures ranging- from 19^ 

 to 23- C. 



He^iidt. — In the check tubes at the end of IS hours there was a slight to 

 very slight growth. On the eighteenth day from one-fourth to three- 

 fourths of the slant surface in these tubes bore a thin bright yellow 

 growth, which never increased much. The development of the germ 

 in the tubes which received the diastase was plainh' different. At the 

 end of 48 hours the growth was distinctly yellow and much better than 

 in the check tubes. On the ninth day the principal difference was still 

 the amount of growth which was several times that in the check tubes. 

 On the eighteenth day the growth was dirty yellow, wet-shining, and 

 copious, i. e.. at least 10 times as much as in the check tubes. The dif- 

 ference in color was very decided. The slime in the check tubes was 

 pure yellow: that in the others was dirty yellow, verging into brown- 

 ish. The tubes were now thought to be rather too dry. and 2 c. c. of 

 sterile Potomac River water was pipetted into each one, the result being 

 a somewhat increased growth. On the forty-fourth day the growth in 

 the check tubes was still feeble and much less than in the tubes which 

 received the diastase. The sul)stratum of the latter had become brown- 

 ish-white with the merest trace of pink in it. The same stain appeared 

 in the check tubes, but was much feebler. 



Tubes of Ps. campeMris and Ps. jjhaseoli yielded some instructive 

 comparisons. In the check cultures, on the sixteenth day, the growth 

 of these two germs was at least 20 times as abundant as that of Ps. 

 Jiyaclnthi. On the seventy-third day, in the check tubes, the layer 

 of Ps. hyacinthi was still feeble, and was still distinctly yellow; 

 that of Ps. carnpestris and Ps. pJuiseoU was KM) times as abundant and 

 had lost all of its pure yellow color, this having changed into a decided 

 brown. The starch in the check tubes of the hyacinth germ was as 

 firm, elastic, and insoluble as when first inoculated, and was but little 

 stained: that in the corresponding tubes of Ps. cahipestris and Ps. 

 phaseoli was gray, soft-nuishy, and soluble in water. Tested in alco- 

 hol-iodine diluted with 50 volumes of distilled water, the check cultures 

 of Ps. hyacinthi gave a strong starch reaction: those of P^. vampestris 

 and Ps. jyhaseoJl gave no color reaction whatever. One culture of each 

 was also tested with Soxhlet's solution for the presence of reducing sub- 

 stances. Ps. oimpestris and Ps. phaseoJI each reduced 25 c. c. of the 

 standard solution of copper sulphate (34.639 grams of c. p. CuSO^ 5 H.^O 



