American Fisheries Society. 73 



•and witli this domestication is largely inconsistent, because there 

 must be consideral)le divergence from nat\iral conditions. 



As for a remedy for the disease, to apply to trout actually 

 affected, I have none to offer. It is not probable that any will be 

 found. In many human infections the best that can 1)0 done is 

 to give the patient the best chance possible to fight it out by him- 

 self. There are very few specific remedies. The antitoxins are 

 notable instances, particularly di}ihtheria antitoxin, which is a 

 conspicuous triumph of medicine. These will probably not be 

 applicable to fishes. When a trout shows external signs of the 

 disease, he is doomed, and many are before such signs appear. 

 However I have used formalin three different times in dilute so- 

 lution as a bath. The idea was that there might be a germicidal 

 action through the gills, but it was scarcely hoped that it could 

 accomplish cures. Formalin is an aqueous solution containing 

 40 per cent, of formaldehyde gas. The bath contained one-third 

 of 1 per cent, formalin or a little more than one-tenth of 1 per 

 cent, formaldehyde. Fry endured tliis withoiit injury for about 

 five minutes, yearlings for about ten. On the first occasion there 

 was no immediate falling off in the death rate, but after some 

 weeks the infection subsided and a portion of the 1)rood sur- 

 vived. It was an open question whether or not this was due to 

 the treatment. On other occasions it was applied to fry and the 

 death rate went up instead of down. I conclude that this sort of 

 medicine is useless, and do not believe that any treatment is of 

 any avail. The cure is nothing, the prevention everything. 



At one station the disease was checked by the transfer of the 

 trout to certain large earth ponds which contained an abundance 

 of natural vegetation. In fact most of the conditions to which 

 wild trout are subject were supplied by these earth ponds. They 

 were very much larger than the wooden ponds. Xow I believe 

 there was more prevention in this than cure. The unaffected 

 individuals merely failed to take up the infection, and the chief 

 factor that enabled them to avoid it was the dUuilon of the infec- 

 tion, and the })revious freedom of the pond from infection. It 

 was somewhat like returning the trout to a natural stream. They 

 separate, there is more space between the individuals and there 

 are fewer germs to each cubic unit of water. Many fish within a 

 small space is of course a necessity in domestication. This is a 



