■bhe liquid ether. When the ether had completely disappeared from the 

 vial, a sterile cotton plug was substituted for the rubber bung. The 

 flask was then allowed to stand at 37° C. until the odor of ether was 

 no longer perceptible. This procedure resulted in the destruction of 

 60 tc 75 percent of the original microflora. 



After adding an initial inoculum of 2,000 ± 200 B. salmonicida 

 per ccc to ether- treated undiluted sewage, rapid multiplication of the 

 bacterium occurred throughout the first 2 days, at the end of which 

 time n-jmbers amounted to 700^000 per cc, rr- an increase of 350- fold 

 the original inoculum. Multiplication conti..ued to a still higher 

 degree, and by about the fifth day B. salm.onicida colonies (on agar 

 plates) were uncountable. On the seventh day numbers were 1,000,000 

 per cc, and a subsequent minor fluctuation was followed by a fairly- 

 rapid drop over a period of 6 days when the count was reduced to the 

 neighborhood of only 70 per cc. A second sharp rise occurred over the 

 succeeding 9 days, finally followed by a gradual and irregular decrease 

 in numbers over 43 days. The last recovery of B. salmonicida occurred 

 on the sixty-seventh day after inoculation. During the final gradual 

 decrease, a general increase in numbers of native sewage colonies was 

 noted, although counts were not made (Duff et al. 194.0). 



Saprophytic Existence and Survival of E. salmonicida in Dead Fish 



Evidence was obtained by the Purunculosis Committee (1933) that 

 Bo salmonicida survives in the furtmcles of dead fish and is still 

 virulent after 6 days at a temperature of about 4.0° F. (5° C ). 



The results of viability studies show conclusively that B. 

 salmonioida is an obligate parasite Tdth no power of existing as a 

 saprophyte under natural conditions. Although it has been found to 

 survive up to 67 days in ether- treated sewage (Duff et al. 1940), its 

 existence in river and tap water is short, a few days at the most. 



Ciiltural Characters 



Relation to free oxygen 



Be salmonicida is aerobic arid facultatively anaerobic (Williamson 

 1920, Dij.ff'and Stewart 1933 )« Pigment production does not occur 

 aiiaerobically (Williamson 1928). 



Agar 



Growth on agar media is good. Emmerich and Weibel (1894) found 

 that at first grovrth on agar was whitish gray_, later becoming yellowish. 

 Af1:.er some weeks, however, cultures became brownish. Although Plehn 



10 



