346 W. A. HAGAN 



nosis is concerned but the pig usually succumbs in from one to four 

 days with a malignant oedema type of infection. The anthrax 

 organism, if it was originally present, has been destroyed by the 

 putrefaction. 



In other cases, microscopic examination of direct smears 

 having shown but very few anthrax-like organisms or none at 

 all, when the culture shows only a few miscellaneous colonies, 

 none of which resemble anthrax, a negative diagnosis is made 

 without subjecting the material to a guinea-pig test. 



A glance at the plates after incubation will serve to show a 

 worker with any experience with the subject whether either 

 anthrax or what I refer to as "anthrax-like" colonies are present. 

 The most striking character of these colonies is their "ground 

 glass" appearance, especially at the margins. To the unaided 

 eye, the colony appears like frosted glass. The reason for this 

 ground glass appearance may be readily appreciated when the 

 colonies are moderately magnified. Just as ground glass has 

 its well known opaque, whitish, velvety appearance because of 

 numerous small facets the surfaces of which are facing in many 

 directions and which reflect light from just as many directions 

 as there are faces, so do these colonies have this appearance 

 because they are made up of bacterial filaments arranged in 

 parallel to form bundles which run in many directions and which 

 reflect light as do the facets of the glass. The less the tendency 

 of the organism to arrange itself in parallel chains the finer does 

 the texture of the ground glass become. In colonies of B. 

 anthracis the bundles are larger than in most anthrax-like colonies 

 so the reflecting facets are larger and the texture of the ground 

 glass is coarser. 



The diameter of the colonies varies, depending on the number 

 on the plate. When not crowded anthrax colonies will reach a 

 maximum diameter of about 5 mm. If given plenty of room 

 some of the anthrax-like colonies will identify themselves by 

 spreading and becoming of much greater size than a true anthrax 

 colony ever reaches. This is not always true, however, especially 

 in a primary culture and the plates as made direct from the 

 suspected material, do not always allow sufficient room for this 

 growth to occur. 



