MARCH 57 



proved illusory. It used to be supposed that those fish 

 which could reach the sea before the disease ended fatally 

 met with a natural cure, because the fungus disappeared 

 under the influence of salt water. But the fungus is now 

 shown to be only the outward and visible sign of the 

 inward and deadly morbus, and it is discouraging to find 

 that the new bacillus thrives well in a salt medium, and 

 best under a low temperature. Mr. Patterson ascertained 

 that it multiplied apace in a freezing mixture of ice and 

 salt, whereas a temperature of 100 deg. Fahrenheit is fatal 

 to it. One precaution he recommends to be observed by 

 owners of fisheries. The bacillus is easily transmitted 

 from dead diseased fish to living healthy ones in the 

 same water; wherefore it is obviously expedient that 

 dead and dying fish should be removed from the river 

 as speedily as possible and destroyed by burning. The 

 common practice of burying them within the water- 

 shed is futile, for the germs are preserved alive in the 

 earth till the next flood carries them back into the 

 stream. 



There is a widespread fallacy among fishermen that 

 outbreaks of salmon disease are the result of an over- 

 stock of fish. This belief has already been the cause of 

 a lot of mischief. Owners of rivers have been positively 

 afraid of so regulating nets, etc., as to increase the 

 abundance of fish. There is absolutely no ground for 

 this arbitrary and misleading hypothesis. Of course a 

 given percentage of diseased salmon will attract more 

 attention when the stock of fish is large than when it 

 is small ; and people unaccustomed to sound inductive 

 process jump to the conclusion that the disease arises 

 from overcrowding. 



