124 A NEW BACILLUS PATHOGENIC TO FISH, 



and near the epidermis, while a third was found deep down in 

 the tissue near the vertebral column on the reverse side and 

 about midway between the first two lesions. The peritoneal 

 cavity was distended with a quantity of a whitish fluid. The in- 

 testines were swollen with gas and had the blood-vessels congested. 

 The liver was mottled, the gall-bladder distended. The blood 

 vessels of the stomach were slightly congested; those inside the 

 swim bladder showed much congestion. The heart, kidneys and 

 spleen appeared normal. The colour of the muscles generally 

 was bluish with a pink tinge. The gangrenous portions of the 

 muscles were cream-white and brittle as in the case of the 

 trevally, and they swarmed with bacilli. When small portions of 

 the heart-blood and of the three gangrenous localities were 

 inoculated into liquefied culture media, there were obtained 

 colonies of the bacillus and no other organism. The spleen and 

 peritoneal fluids contained a mixture of organisms, including the 

 bacillus. The liver was sterile. 



Characteristics of the Orcanism. 



Microscopical appearance. — The bacilli appear as large rods, 

 with rounded ends, and measure 0-8 : 2-3-6 /x in bouillon 

 culture. They grow singly, in pairs, and short chains in liquid 

 media. On solid media they grow as long chains or filaments, 

 which lie parallel with one another. The cells show, when stained 

 with methylene-blue, a granular structure. They stain deeply 

 by Gram's method. 



Spores. — The rod easily forms a central spore, at first round, 

 then becoming oval, and finally measures 1 : 1-5-1 -6 /x. Although 

 the spore is broader than the bacillus, the latter does not assume 

 a marked Clostridium appearance, owing to the remains of the 

 rod broadening as sporulation proceeds. 



Motility. — The younger bacilli in bouillon are actively motile, 

 the motion being fish-like. The older bacilli and those grown on 

 solid media either move extremely slowly or are non-motile. The 

 flagella are terminal or irregularly distributed over the surface; 

 in most cases there is a single flagellum at one end of the rod. 



