DIAGNOSIS OF ANTHRAX 347 



Stained preparations will serve to eliminate many of these 

 colonies by showing organisms of a morphology differing suffi- 

 ciently from B. anthracis to admit of a negative diagnosis. These 

 differences are principally in greater length and the possession 

 of ends markedly rounding. Stained preparations will by no 

 means eliminate all of these organisms however for some show 

 bacteria indistinguishable, as far as I am able to determine, 

 from true anthrax. Hanging drops will also eliminate many of 

 these organisms by demonstrating rapid motility and I have 

 no doubt but that other tests would eliminate still others not 

 detected by the methods given. These are all time consuming, 

 however, and, as I have said, this is of importance. 



An easy and rapid method has been devised which, during a 

 period of over a year, has picked out readily all true anthrax 

 cases (about 15 in number) from among a considerable number 

 of negatives (about 70), the inoculation of guinea pigs being the 

 criterion. This method consists simply in examining directly 

 with a high power objective the minute structure of the suspected 

 colony. When examined grossly or with low powers, these 

 colonies are so similar as to make differentiation difficult in 

 many cases; but when submitted to a greater magnification 

 differentiation has been made with ease in all cases yet submitted 

 to the test. Some of these differences are difficult to explain 

 and can be appreciated only by actual trial. The method gives 

 at once the morphology of the organism, whether or not it is 

 motile, whether or not spores are present, their location and 

 shape if present, and the relation of the organisms to each other 

 in the colony. 



The suspected colony is prepared for examination by laying 

 aside the lid of the Petri dish and dropping a flamed and cooled 

 cover glass directly upon its surface. If one edge of the cover 

 glass is first touched to the surface of the medium at one side 

 of the colony to be examined and then gently lowered with a 

 pair of thumb forceps air bubbles will be avoided as there is 

 sufficient water of condensation on the surface of the agar to 

 fill the space beneath the cover-glass. A drop of immersion oil 

 is now placed on the cover glass, the open plate placed on the 



