57 



Growth on Potato with Addition of Diastase of Malt. 



This mcdiiini coiisisti'd of 4 potato cylinders from tlu^ same tuber as 

 3U1. to each of which was added r)(M) inillioraiiis of Merck's "diastase 

 of malt absolute." After remain iiig over nioht in a water bath at 50° 

 C, these tubes were sterilized by steaming about !^o minutes on 4 

 consecutive days. Each tube received a large loop from a beef -broth 

 culture 11 days old — the same tube that was used to inoculate the tul)es 

 of pot«ato-maltose-dextrine. Two tul)es without tlie disastase were 

 inoculated for comparison. The tubes w^ere kept together in the dark 

 at room temperatures of 20^ to 25^ C. 



Result. — B}^ the end of the third day the check tubes had developed 

 a thin, distinct, yellow growth over nearly the whole of the exposed 

 part (one-third) of the cylinder. The progress of these check cultures 

 from this time on was typical for Ps. hyacinthi^ there never being any 

 copious growth or any development of the yellow^ slime under the 

 water. The tubes to which the diastase was added were under obser- 

 vation 55 days. In 3 of them there was never an}' growth. In 

 the fourth tube grow^th was retarded until the eighth day (tempera- 

 tures 20^- to 23^' C), on which date a yellow^ patch 1 cm. square was 

 visible. On the twent}- fourth day the organism had entireh" overcome 

 the retarding action of the medium and had made an abundant, dis- 

 tinctly yellow, smooth, wet-shining growth over the whole cylinder 

 down into the w^ater and up on the wall of the tube. This growth was 

 estimated at 50 times that in the check tubes and Avas greatly in excess 

 of any growth ever before obtained upon potato. 



The 3 tubes in which there had l)een no growth were reinoculated 

 on the twenty-fourth day, using for one a large loop of yellow slime 

 from one of the check tubes, and for each of the other two an equally 

 large loop of slime from the other check tube. This slime was rubbed 

 carefully over the surface. No growth ensued, although the tubes 

 were watched for a month. The fluid in these tubes w'as neutral to 

 litmus, or ver}' feebh^ acid when dry, and the restraining influence 

 was therefore attributed to an excess of maltose or dextrine liberated 

 ))y the diastase. On mashing one of these cylinders in alcohol-iodine 

 water there was no starch reaction whatever nor any red reaction. 



Potato Starch in Pei^onk Water with Diastase. 



This medium was prepared in test tubes of resistant glass, using about 

 1 gram (estimated dry weight) of freshly pr(>})a]"ed thoroughly washed 

 potato starch to al)out U c. c. of distilled water which had received 4 per 

 cent of Witte's peptonum siccum. The tubes were then put into the 

 steamer and the starch solidified in a slanting jmsition. Some of these 

 tul)es were held as checks, and the surface of the remainder was flooded 



