BACILLUS DIPHTHERIA COLUMBARUM. 327 



semi-transparent layer ; on potatoes a deposit which is 

 only distinguishable from the surface of the potato by 

 having a somewhat greyer colour. Pigeons inoculated Experiments 

 subcutaneously with pure cultivations of these bacilli on ammals - 

 are attacked by inflammations ending in necrosis ; after 

 inoculation on the mucous membrane of the mouth 

 a morbid process develops, which completely coincides 

 with the natural infective disease. Sparrows and rabbits 

 are susceptible to the action of the bacilli ; fowls, guinea- 

 pigs, rats, and dogs are immune, or only show a tran- 

 sitory local aifection. Mice show very characteristic 

 effects ; they die as a consequence of subcutaneous inocu- 

 lation in about five days, and the short bacilli, described 

 above, are found in the blood, and in all the organs, 

 most numerous in the liver ; they lie everywhere in the 

 interior of the blood vessels, and often also in the interior 

 of colourless blood cells. To the naked eye the peculiar Characteristic 

 character of the liver is most striking in the mice, as appe'araiufeT 

 also the marked swelling of the spleen, and the patchy in mice - 

 redness of the lungs ; the liver has a marbled white 

 appearance, due to the fact that in the pale red liver- 

 tissue numerous white irregularly limited patches were 

 present. Under the microscope no liver-tissue can be 

 seen in the neighbourhood of these patches, and the 

 nuclei do not stain at all ; in the centre of the patches, 

 however, there are dense masses of bacilli within the 

 vessels, which have evidently led to the death of the 

 surrounding tissue of the liver over a considerable area. 

 As this post-mortem result is found in all the mice 

 inoculated, we have in the inoculation of mice with these 

 bacilli the best means of recognising them. 



These bacilli must therefore be looked on as the ex- 

 citing agents of pigeon diphtheria. As they were not 

 found in human diphtheritic membranes, even after the 

 most careful microscopical examination, we must con- 

 clude that the two forms of diphtheria are not etiologi- 

 cally the same. The view that human beings can 

 become affected with diphtheria from infection from 

 diseased pigeons and fowls has been repeatedly ex- 

 pressed, but has been objected to by a number of 



