THE CAUSE OF BLACK DISEASE. 



Spores. These are almost invariably situated terminally or sub-terminally, 

 and are distinctly oval, measuring about T75 to 2 -7 5 by about 1*25 microns. 

 They distend the bacillary rod. Spores are not often found in the lesions if 

 the latter are fixed directly after death, but they will be found if there has 

 been a few hours delay in fixation. They are readily formed in media 

 containing serum, but very few in any media containing glucose. 



Staining reactions. The bacilli stain with any of the basic aniline dyes 

 and are Gram positive ; but in sections, if the tissue has been preserved any 

 length of time, the contained bacilli cease to retain the stain by the method 

 of Gram or Gram-Weigert, or retain it only feebly. By the Claudius method 

 they stain a deep purple. For the demonstration of the bacteria in sections, 

 the latter has been the method of choice, as the decolorisatiori of the tissue 

 elements can be carried to a considerable length without decolorising the 

 organisms. In sections also, the Giemsa and Kiihne-Nicolle methods 

 have given good results, but more care has to be observed in the 

 manipulation. 



Occurrence in the body. In naturally occurring cases, if the autopsy be- 

 held immediately after death, the baccilli will be found confined to the 

 hepatic lesion or lesions. The unaffected liver tissue, other organs, exudates v 

 blood, &c., appear to be quite free from them, even on cultivation. Conse- 

 quently the condition is really a toxaemia. There is every reason, however, 

 to believe that invasion of the adjoining liver tissue, and possibly the blood, 

 may take place soon after ckeath, together with invasion from the intestines 

 of cadaver bacilli. Invasion by the latter, of course, invariably occurs unless 

 the tissue is removed directly the animal dies. In two cases where the post 

 mortem was unavoidably delayed for about an hour, microscopical examina- 

 tion of the affected liver showed that the bacilli in the necrotic lesion had 

 already begun to extend through the zone of reaction into the unaffected 

 liver substance. 



In experimentally infected cases, the disposition of the causal organisms 

 depends upon the method of introduction. When inoculated subcutaneously r 

 the bacilli are found in greatest number in the neighbourhood of the inocula- 

 tion site. If the injection has been made intramuscularly, they will be found 

 numerously present in the inoculated muscles, but very frequently the sub- 

 cutaneous exudate immediately in their vicinity may be very scanty in 

 bacilli. Although this exudate may be abundant, and the causal organisms 

 numerous in it around the site of inoculation, it is, nevertheless, difficult by 

 the microscope to find bacilli at any considerable distance from this area, 

 and at times in such cases even cultural methods fail to reveal them. The 

 thoracic, peritoneal, pericardial, and intermuscular exudates (when the latter 

 occurs some distance from the inoculation area) when present in such 

 experimental cases are bacteria free. 



Cultural Characters. This description, as noted in the footnote on page 3, 

 is incomplete, and relates mainly to culture in liquid media. The bacillus is 

 an anaerobe, and grows best at body temperature, but, like other anaerobes,. 



