20 



B. typhosus in the oyster could be expected to be small, as 

 for instance in the later oysters of a series, more than one 

 Drigalski plate was made directly with the fluid of the 

 minced oyster, each plate receiving * 1 c.c. After having, by 

 means of the sterile bent glass rod, carefully and thoroughly 

 and uniformly rubbed the material over the surface of the 

 dry medium (all previous moisture having been previously 

 removed by allowing the plates to evaporate it spontaneously 

 for 2-3 hours in the incubator), the plates are transferred to- 

 the incubator at 37 C. 



As mentioned above, the typhoid colonies are noticeable 

 already after 24 hours, and a preliminary counting can now 

 be made, but it has to be controlled after the plate has been 

 placed back in the incubator for at least another day, gene- 

 rally two more days, because the character of the colonies- 

 can by this time be considered fully established. By this 

 time, colonies, which after the first 24 hours' incubation 

 might be doubtful typhoid colonies, can with certainty be 

 declared to be or not to be typhoid, and all those which 

 show the above differential characters in the same manner 

 may be taken to be typhoid colonies ; agglutination test and 

 subcultures on gelatine, and if necessary in other media, are 

 made, selecting at random from different quarters of the 

 plate one colony for the purpose. Since after two, or better, 

 three, days' incubation at 37 C. the character of all the 

 colonies in the plate typhoid and not typhoid is fully 

 established, and since the typhoid colonies are distinct and 

 different from all others by colour, size, general aspect, and 

 shape, there is no difficulty in at once diagnosing them and 

 to recognise their identity,* and it is not therefore necessary 

 to test more than a few of them for agglutination and sub- 

 culture on gelatine. The growth on this gelatine subculture 

 (after 24 hours' incubation at 20 C.) is inspected, examined 

 in the hanging drop and tested for agglutination, and must, 

 if B. typhosus, comply with the required tests : on gelatine 

 translucent filmy growth, composed of cylindrical motile 

 bacilli, agglutinating markedly and instantaneously with a 



* See photograms accompanying this Report. 



