62 



thin distinctly yellow layer; i. e., there was several times as much 

 growth as in the check tube, but there was no visible diastasic action. 

 The growth of P.s. phaseoU on the check was now at least 100 times as 

 abundant as that of Ps. hyacmthi on the same medium. 



On the starch jelly with addition of the dextrin Ps. carn.pestris and 

 Ps. phaseoli both made a good growth. On the seventh daj^ Ps. 

 canvpestris covered the whole surface of the long slant to a depth of 1 

 to 3 millimeters with a semifluid, smooth, wet-shining slime, and the 

 diastasic action now involved nine-tenths of the starch. The conver- 

 sion of the starch was clearly visible, proceeding slowh^ and uniformly 

 from the surface of the slant inward. There was a distinct line of 

 demarcation between the converted and unconverted starch. The 

 latter was bluish white, opalescent, translucent, firm, elastic, insolu- 

 ble; the former was dead white, opaque, soft, inelastic, and soluble in 

 water on gentle shaking. This part gave no color reaction whatever 

 on adding iodine water. On washing it all out the unchanged one- 

 tenth in the bottom of the tube was seen to have presented the shape 

 of the original slant, and on adding the iodine water it became bright 

 blue. In the corresponding tube of Ps. phaseoli the growth at this 

 time appeared to be equally as good, but only about two-thirds of the 

 starch was converted. The diastasic action proceeded from the surface 

 inward in the same regular manner, the line of demarcation between 

 converted and unconverted starch was equally sharp, and the converted 

 portion had all the peculiarities recorded for that acted on by Ps. 

 catnpestris. A fragment of this soft white starch as big as two peas 

 was stirred up in 5 c. c. of the very sensitive pale brown alcoholic 

 iodine water, but no color reaction could be obtained. This changed 

 starch included all of the outer 5 or 6 millimeters of the slant; on fill- 

 ing the tube part full of water and shaking gently all of it dissolved 

 readily, leaving in the bottom a translucent, bluish white, insoluble, 

 miniature slants which immediately reacted bright blue on pouring in 

 the same iodine water. These experiments show that the presence of 

 albuminoids is not necessar}' for the production of the diastasic fer- 

 ment and also that it is excreted b}' these two species in the presence 

 of an abundance of readily assimilable food. 



On the twelfth da}', in the check tube of Ps. Kyacinthi^ the thin, 

 pale yellow gi-owth had extended over most of the slant surface, but 

 it was still not one-hundredth part as abundant as in the correspond- 

 ing tube of Ps. phaseoli^ and there was no evidence of any dia- 

 stasic action, whereas in the latter more than nineteen-twentieths of 

 the starch had been digested. In the tube which received the dextrin, 

 Ps. hyacinthl had made, on this date, a good, bright yellow but rather 

 dry growth over the whole surface. On the thirtieth day, in this 

 same medium, there was a plentiful, smooth, wet-shining, bright 3^el- 

 low slime over the whole surface, i. e., growth enough to hide the sub- 



