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A NEW BACILLUS PATHOGENIC TO FISH. 



By R. Greig Smith, M.Sc, Macleay Bacteriologist. 



(Plates viii.-ix.) 



A few fishes which were supposed to have died of some obscure 

 disease were received from the Fisheries Department towards the 

 end of March. They came from Lake Illawarra, an inlet from 

 the sea about 33 miles south from Sydney. The flesh of the fishes 

 was of a greenish hue and somewhat congested in the neighbour- 

 hood of the main blood vessels. The vessels of the stomach and 

 intestine were also much congested, but beyond these appear- 

 ances there was nothing abnormal to be seen. When, however, 

 portions of the various muscles and organs were examined 

 microscopically a large rod-shaped bacterium with rounded ends 

 was invariably found in all the fishes. In some cases the organisms 

 had completely filled the smaller blood vessels. Portions of fluid, 

 juice or pulp from the parts examined gave rise, when inoculated 

 into culture media, to many bacterial colonies, among which 

 those containing the large rod-shaped organism predominated. 

 The organism readily produced spores, and accordingly by the 

 nomenclature of Lehmann and Neumann and others it is a 

 bacillus. 



In order to test the pathogenicity of the bacillus, an agar 

 culture which had partly sporulated was distributed in 4 c.c. of 

 normal saline and 0"5 c.c. injected under the skin of a guinea-pig. 

 No reaction followed, and the animal remained in health. 



It now remained to test its pathogenicity to fish, and with this 

 object in view three fishes comprising a White Trevally, Garanx 

 georgianvs, C. & V., a large and a small Mullet, Mugil sp., were 

 inoculated with - l to - 3 c.c. of a similar suspension of bacilli 

 and spores subcutaneously in the left upper dorsal region between 

 the median fin and the tail. In 24 hours the movements of the 

 fishes had become sluggish. The trevally showed a white patch, 

 from which the scales had fallen, stretching for about an inch 

 and a half forwards and backwards from the point of inoculation. 



