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consideration. From what we observed subsequently (1922) we feel sure that 

 in addition to the illegal dynamiting of fish, which accounted for some of the 

 mortality, there was also an epidemic in progress. 



Towards the end of August, 1922, dead and dying fish were seen in large 

 numbers floating down the Brisbane River in the vicinity of the Commonwealth 

 Prickly Pear Laboratory, Sherwood, and on inquiry it was ascertained that the 

 epidemic had been in progress for at least four weeks previously. Early in 

 September the condition disappeared. We estimated that over 90 per cent, of 

 the dead fish observed by us were the so-called Brisbane River perch, Sciaena 

 aiistraUs, Gnthr., an estuarine species belonging to the Sciaenidae. The remainder 

 consisted of catfish (Tandanus tandamis and Ncosilurus hyrtlii) and a few John 

 Dories (Zens faber, L.). Moribund fish were seen to be swimming slowly on 

 their sides on the surface of the water and unable to maintain their balance. A 

 condition of acute dyspnoea seemed to be present. Hawks, fish-eagles, cor- 

 morants, and other birds were actively engaged in feeding on the fish ; in fact, 

 it was their activity which led us to discover that an epidemic was in progress. 



Post-mortem examination revealed a condition resembling septicaemia. All 

 the peritoneal blood-vessels were considerably distended, and the liver was putty- 

 like, though its vessels were much engorged and showing plainly on the surface 

 in places. The heart seemed normal, but the spleen was black and in many cases 

 obviously necrosed. The gall-bladder was slightly enlarged and the kidneys 

 congested. The intestine was empty except for the presence of a milky fluid. 

 The marked fatty degeneration reported as occurring in material from the fresh 

 waters of Western Queensland was not present in the Brisbane River specimens 

 under examination. 



Smears taken from the liver, kidney, and spleen of dying fish showed 

 abundant, fairly large diplobacilli, and cultures made from the organs revealed 

 the same organism. The latter was pleomorphic, its simplest form being obtained 

 on agar, where it appeared as a micrococcus with scattered bacillary forms. 

 In liquid media it occurred as a bacillus, reaching a maximum length of 2 y. 

 by 85 IX, though many appeared to be undergoing a constriction into cocci. The 

 larger rods were often slightly curved. The arrangement was commonly that of 

 diplobacilli. The organism was larger when growing in blood than on artificial 

 media, and nearly always assumed the form of a diplobacillus. 



It was gram negative and stained readily wath the usual aniline dyes, a 

 bipolar efifect often being seen. Growth occurred on ordinary solid and liquid 

 media at a titre of +15 to +05 acid to phenolphthalein. Unless otherwise 

 stated, the following remarks relate to growth in media at these two titres : — 



Bouillon: — A good growth was present in 18 hours with clouding of the 

 medium. After seven days a sediment was produced but no pigment, while after 

 a lapse of 15 days a surface scum appeared and sedimentation was increased 

 but without pigmentation. 



Agar: — There was a good growth at +1'5 and also at +0 5. appearing 

 dirty white by oblique light. Agar stabs showed no special features. On Agar 

 plates the superficial colonies were round, slightly convex, with a well-defined 

 outline, and when viewed microscopically by transmitted light appeared to be 

 granular and to have a crenate margin. Well developed colonies were translucent 

 and faintly yellowish. 



Gelatin stab: — A filiform growth but no liquefaction, even in cultures a 

 week old. 



Blood serum : — Good growth ; no liquefaction ; no pigmentation. 



Milk : — Good growth on litmus milk ; no coagulation. On the first day the 

 reaction was either unchanged or very faintly alkaline. On the second day the 

 alkalinity was more marked, becoming pronounced on the succeeding day. The 

 milk was not peptonised, even after four weeks. 



