156 American Fisheries Society 



Evidently the tanks of the Aquarium have escaped in- 

 fection since it is well known that the most fatal epidem- 

 ics are from this cause, often leading, in the Great Lakes 

 to the death of countless fish. They commonly infect the 

 muscles and subcutaneous tissues, producing tumor- 

 like swellings which project under the skin and may break 

 down into great ulcerations. Sometimes they show only 

 in the form of small whitish nodules in the internal or- 

 gans, at others in large nodular masses like white tapioca 

 or sago which fill the abdominal cavity, being attached to 

 the peritoneum and the internal organs. The escape of 

 the parasites from ulcers and from dead and decomposing 

 fish spreads the disease and the most drastic measures are 

 necessary if this is to be prevented. The fish which I have 

 found to suffer most from this disease were perch, floun- 

 ders, alewives, smelts, hake, pickerel and some of the min- 

 nows. 



Certain bacterial infections have, however, caused the 

 loss of many fish in the Aquarium in the course of the 

 past winter. In these there appeared peculiar ulcerations 

 of the skin, which in a short time so progressed as to 

 cause the death of the fish. They are sometimes numerous 

 and large and often burrow under the skin or even ulcer- 

 ate into and through the bones, including those of the 

 head. The ulcer usually shows a dirty gray slough which 

 discharges pus. The neighboring scales are loosened and 

 the skin discolored. Apparently these ulcers begin as ac- 

 cesses beneath the skin, and after death the liver, spleen 

 and kidneys show scores of small abscesses scattered 

 throughout their substance. Cultures were made by Prof. 

 Zinsser, of Columbia University, who found a bacillus 

 growing best at low temperatures, which, when inoculated 

 in pure culture into normal fish reproduced the disease 

 even to the extensive ulceration of the skin. In both the 

 original lesions and in those experimentally produced the 

 bacillus was demonstrated in smears and in sections. This 

 study is still under way and will be published when com- 

 pleted. As far as I know, this disease affects only the 

 fish in the Aquarium, not those taken freshly from the 



