Christison and associates (1938) found that no prevalent bacteria derived 

 from fish or water have proved to be susceptible to this phage or 

 responsible for its propagation. On the contrary, however, Blake (193.5) 

 found Escherichia coli and Shigella dysenteriae susceptible to the phage 

 though less markedly so than B. salmonicida . Since relatively little 

 work has been done on this subject^ one might feel reluctant to overlook 

 the earlier conclusions of Blake (1935) for those of Christison and 

 associates (1938). 



Christison and associates (1938) considered whether a phage, 

 originally associated with some water organism, under the conditions of 

 experiments might become rapidly adapted to B. salmonicida and lose its 

 activity towards its original bacterial host. However, they pointed 

 out that while adaptation of a bacteriophage from one species of 

 organism to another has been claimed (d'Herelle 1926), this has only 

 taken place gradually, and it is difficult to postulate the rapid 

 adaptation that would explain these findings. Christison and others 

 (1938) also pointed out that the demonstration of this phage involved 

 the bringing of water into contact with the laboratory cultures of B. 

 salmonicida . Such cultures by themselves were proved to be free from 

 phage and did not yield it when gro^vn in broth under the same conditions. 

 Therefore these results might even raise the question whether the phage 

 originated de novo during the experiment. However, water which had been 

 heated to 100° C. (to destroy any phage present in it) and then tested, 

 did not lead to the demonstration of B. salmonicida phage. 



The observations on B. salmonicida phage are of considerable 

 interest but as Christison and others (1938) point out, no definite 

 conclusions can be drawn apart from the fact that a phage active towards 

 B. salmonicida and propagating with this organism in laboratory cultures 

 is very widely distributed in natural waters, and that its presence in 

 water cannot be necessarily correlated with the presence of f urunculosis . 



PATHOLOGY 



The term "f urunculosis" with reference to fish is a misnomer, for 

 the lesions of this disease are not analogous to furuncles as they occur 

 in the human subject. The so-called furuncles of fish are areas of 

 necrosis in which there is no outstanding leucocytic infiltration. The 

 pus-like discharge from these areas is not true pus, but consists of 

 liquefied necrotic tissue showing microscopically muscle fibres, blood 

 cells, and bacteria. However, the term "f urunculosis" with reference to 

 fish should stand, as time has given it priority. 



The symptoms of the disease are not always obvious and those 

 lesions present may be masked with fungus grovrbh (Plehn 1911). Davis 

 (194.6) found in the case of fingerling trou.t that usually the only 

 evidence of a lesion from the exterior is an irregular dark blotch just 

 beneath the skin on one side of the body. This blotch ordinarily is 



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