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Dr. P. F. Frankland. 



[June 10, 



In studying the behaviour of parasitic micro-organisms under 

 these conditions, I have selected three forms which are recognisable 

 with particular facility, owing to the highly characteristic appearances 

 to which they give rise when cultivated in the gelatine-peptone 

 medium. 



These forms are — 



1. Bacillus pyocyaneus. 



2. Finkler- Prior's Comma Spirillum. 



3. Koch's Comma Spirillum. 



The pure cultivations of these organisms were obtained directly, in 

 the case of the first two mentioned, and indirectly, in the case of the 

 third, from the laboratory of the Hygienic Institute of Berlin. 



1. Appearance of the Bacillus pyocyaneus in Gelatine-tube Cultivations. 



At 20° C, within twenty-four hours of inoculation, the path of the 

 needle is indicated by incipient liquefaction at the surface, which as 

 growth proceeds undergoes funnel-shaped depression, the fringe of 

 which soon exhibits blue-green fluorescence. The diameter of the 

 liquefied portion increases until the whole width of the tube is 

 affected, the downward extension of liquefaction proceeding in the 

 form of an inverted cone, in the apex of which a flesh-coloured pre- 

 cipitate is formed. The bine-green fluorescence is seen only on and 

 near the surface. Ultimately the whole of the gelatine becomes 

 liquid, and of a dirty green colour. 



Appearance of the Bacillus pyocyaneus in Gelatine-plate Cultivations. 



At 20° C. the colonies are generally distinctly visible on the second 

 day as small opaque light green disks, the whole plate presenting a 

 blue-green fluorescence when viewed by reflected ligbt. The size of 

 the colonies is dependent upon the number present on the plate, 

 being exceedingly minute when the latter is densely crowded, and 

 reaching several millimetres in diameter when only a few are scat- 

 tered over the surface. The amount of liquefaction also varies 

 inversely as the number of colonies, but even after considerable lique- 

 faction has taken place over the surface of the gelatine, the indi- 

 vidual colonies remain perfectly distinct, and do not become confluent, 

 and so lose their identity, as is the case with many liquefying orga- 

 nisms. Not unfrequently, especially when there are comparatively 

 few organisms on the plate, those situated on the surface give rise to 

 a remarkable and very beautiful flocculent expansion of irregular 

 contour and sometimes several millimetres in diameter. 



The plates possess a highly characteristic and very nauseous odour, 

 which is at once apparent on opening a dish in which they have been 

 developed. Viewed under the low power of the microscope each 



