Stability of virus. --Diseased material was subjected to freezing, 

 heating, suspension in glycerol, and to different hydrogenion concentra- 

 tions to determine the effect upon the infectious agent. 



The temperatures used in freezing were 0* and -iiO" F., which will 

 be discussed in greater detail when pertinent. 



The effect of elevated temperatures on a suspension of the in- 

 fectious material was tested by heating aliquots of a suspension at 

 10° intervals from 30* to 100* C. for periods up to 15 minutes before 

 inoculation. Whole diseased fish were also subjected to the same 

 temperatures for 1$ minutes and then placed in contact with healthy 

 fish. 



Aliquots of a virus suspension were adjusted from pH U.O to pH 

 10 oO by the addition of 0.1 N HC1 or 0.1 N NaOH. Each aliquot was in- 

 cubated at room temperature for 1 hour and then returned to neutrality 

 by the addition of equivalents of 0.01 N HC1 or NaOH. Before inocula- 

 tion each aliquot was adjusted so that the final dilution was 10"^-. 



Fish 



Source. — The majority of the experimental fish were 6- to 10- 

 month-old fingerling sockeye salmon which were reared at the Leavenworth 

 hatchery. In addition, fish of the same age groups from hatcheries at 

 the University of Washington, Entiat, Winthrop, and Cook were also used. 



Adult salmon used in these experiments were trapped at the Hock 

 Island Dam on the Columbia River and transported to the Leavenworth 

 hatchery where they were held in rearing ponds for 2 months prior to 

 spawning . 



Other fingerling populations used in these experiments included 

 rainbow trout and chinook and silver salmon. The rainbow trout were 

 obtained from either the University of Washington or the Winthrop 

 hatchery, and the silver salmon were reared at the University of Wash- 

 ington. 



Diseased populations used in the studies in the summer of 1953 

 were from the Leavenworth hatchery. 



Numbers. — There was a considerable variation in the number of fish 

 used in any one experiment, ranging from a minimum of 25 fish to a maximum 

 of 3,000 fish per experiment. In most of the experiments where infectious 

 material was titrated, 25 fish were inoculated with each dilution. When 

 the infectious material was not titrated, a minimum of 200 fish were used 

 per experiment. 



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