145 



alive on potato after 5 months and on agar (stock 553) after 10 months. 

 Several tubes of Ps. j/JMseoll were alive after 5 months on potato. B. 

 carotovorus was also alive on potato at the end of 5 months. 



Resistance to Dry Air. 



Dr. Wakker states that the hyacinth organism remains alive in a dry 

 state for a long time. Only three experiments were made to deter- 

 mine this point, all of which tend to confirm his statement. 



(1) A typical potato culture 9 days old was shaken until nearl}- all 

 of the 3^ellow slime was washed into the 1 c. c. of fluid in the bottom of 

 the tube. Fifteen small drops of this heavily clouded fluid was then 

 spread on 15 small, clean, sterile cover glasses, in a Petri dish, the 

 cover replaced, and the dish set away in a dr}^, dark closet, at 20° C. , 

 for 9 daj^s. At the end of this time 13 of these covers were dropped 

 into as many tubes of culture media^ — beef broth, sugared peptone 

 water, etc. 



Result: Ps. hyaclntld developed after a few days in all of these 

 tubes, showing that some germs were still alive on each cover glass. 

 The time required to cloud these tubes was 3 to 8 days, at 16° to 20° C. 



(2) The remaining 2 covers were kept until the ttTth day, after which 

 they were put into 1 per cent grape sugar peptone water. 



Result: After a few days the fluid in each tube clouded and threw 

 down a yellow precipitate. 



(3) Some weeks later this experiment was duplicated, with the excep- 

 tion that a period of 48 days was allowed to intervene between the 

 spreading of the cloud}^ fluid on the covers and their submersion in 

 the culture medium. In this instance the bacteria were derived from 

 a 9-days-old culture on 3'ellow banana, the slime being rubbed over 

 the clean sterile covers, which were then set away as before. On the 

 48th day 18 of these covers were seized with sterile forceps and dropped 

 into as many tubes of sterile beef broth (stock 382) and set awa}^ in the 

 dark, at 20° to 26° C. 



Result: All but one of these tubes developed Ps. hyacinthi Nine 

 clouded on the 4th day; 5 on the 8th day; 2 on the 12th day. Two 

 tubes were clear on the ITth day, but one of these was cloudy on 

 the 23d day. The other remained clear. These results seem to indi- 

 cate a marked difference in the vitality of individual rods. These are 

 the cultures which were tested for invertase. 



Experiments with Ps. cam2:)estrls and Ps, j^^t^^^oU show that they 

 are also resistant to dry air, l)ut apparently less so thanP*'. hyacinthi. 

 The organisms were dried on cover glasses in a dark closet in the same 

 way as Ps. hyacinthi, except that the temperature averaged" about 5° 

 higher. The covers were inoculated copiously and were side by side 

 in clean covered Petri dishes. Of course those inoculated from the 

 21788— No. 28—01 10 



