Tue SALMON DISEASE. 183 
science it is never quite safe to jump to a conclusion even when 
it lies beyond but a narrow gulf of hypothesis, and no clearer 
instance of the danger of doing so need be sought than that given 
by Professor Huxley’s diagnosis of the salmon disease. It was in 
1877 that attention was first drawn to what was considered a novel 
epizootic attacking salmon in the Esk and Nith, and destroying 
many of them. White fungoid patches appearing first on those 
portions of the fish’s skin which are not protected by scales—the 
head and fin bases—spread rapidly to other parts of the body, 
became confluent, and produced deep ulcers, generally causing 
the death of the fish. Huxley satisfied himself and others that 
the agent in the disease was the minute fungus “ Saprolegnia 
ferax,’’ the same which may be seen in autumn on the bodies of 
dead flies sticking to the window panes, and closely akin to 
“Peronspora,’’ which causes the potato blight. He considered 
that the spores of his fungus, floating in fresh water, attached 
themselves to living tissues of a fish which had received some 
external injury, and multiplying rapidly, penetrated to the vital 
organs. In the year 1903 Mr Hume Paterson announced his 
discovery that “Saprolegnia ferax’’ was not the cause of the 
disease at all, but simply of the mould which grows upon such 
portions of the flesh of salmon as has been previously “ necrosed,’’ 
or killed by another agent, and this agent was revealed to him in 
the form of a uncro-organism, now known as “ Bacillus salmonis- 
pestis.’’ So far from this disease originating in fresh water, this 
bacillus grows well in sea water, where “ Saprolegnia ’’ will not 
grow at all. 
Mr Arnott proceeded to say that it was important and in- 
teresting to recall that so far back as April 23, 1880, Mr J. 
Rutherford, Jardington, read a paper to this society upon 
“Observations on the Salmon Disease,’’ in which he said :—“I 
have not been able to trace the roots of the fungus beyond the 
skin that covers the scales. In making a cut into the fish through 
the fungus, the eye at once is attracted by an inflamed, unhealthy- 
looking stratum of muscle below the skin, of varying thickness. 
In one fish that I examined it extended right through to the inside 
sections of that muscle, and when placed under the microscope 
were seen to be literally one mass of life—that life being a species 
of bacteria. . . . AsIdid most of this work in the winter, when 
the frost was so hard I took advantage of it to freeze parts of 
