

BACTERIOLOGICAL DIAGNOSIS 273 





[3. Summary of diagnostic tests.] 



[As some difficulty may be experienced in differentiating the diphtheria 

 bacillus from other organisms and especially from Hofmann's bacillus it 

 will be convenient to summarize the purely specific characteristics of the 

 organism : references are given to the pages on which these characteristics 

 are discussed in detail and also to the pages on which the reactions under 

 similar circumstances of Hofmann's bacillus are considered : the reader will 

 thus be in a position readily to form a diagnosis. 



The true diphtheria bacillus is characterized by its : 



(a) Macroscopic growth on serum and morphology (p. 250 diphtheria bacillus : 

 and p. 273 Hofmann's bacillus). 



(/3) Power of producing acid in glucose broth (pp. 256 and 274). 



(y) Invisible growth on potato (p. 254). 



(8) The lesions produced in inoculated guinea-pigs (pp. 247, 255 and 274). 



Bacillus pseudo-diphtherice. 



(Hofmann's bacillus.) 



In the mouths of healthy persons and in some cases of non-diphtheritic 

 sore throat a non-virulent bacillus described by Loeffler as the pseudo- 

 diphtheria bacillus is, as has already been indicated, not infrequently present. 



[According to Graham-Smith, Hofmann's bacillus is most commonly found 

 in the throats of the poorer classes, especially the scholars in the public 

 schools (51 per cent, to 56 per cent.). The children attending better-class 

 schools are less commonly found to harbour this bacillus in their throats 

 (8 per cent, and 15 per cent.). In adults the extent of infection is less than 

 in children, but it is greater amongst the poor (20 per cent.) than amongst 

 the well-to-do (9 per cent.).] 



This organism is by some observers (Loeffler, Hofmann, [Cobbett] and others) 

 sharply differentiated from the diphtheria bacillus, while others (Roux and 

 Yersin) have brought forward arguments in favour of its identity with the 

 diphtheria bacillus : in the view of the latter school the pseudo-diphtheria 

 bacillus is merely a diphtheria bacillus 

 devoid of virulence (see also pp. 274 and 275). 



[Morphology. When taken from young 

 serum or alkalized glucose serum cultures, 

 stained with a weak solution of Loeffler's 

 blue and mounted in the stain, the bacillus 

 of Hofmann exhibits great uniformity of 

 type ; it is oval, stains deeply, has no gran- 

 ules, but shows one unstained septum. The 

 arrangement too is quite different from that 

 of the diphtheria bacillus: Hofmann's 

 bacillus ranges itself in parallel groups 

 resembling a paling. Occasionally the or- 

 ganism departs from this typical form, and 

 numerous many-banded forms O3cur ; on 

 sub-culture however these many-banded 

 forms revert to the type already described. Oc. 4, obj. T uh, Zeiss. 



[Staining reactions. Stained with a weak 



solution of Loeffler's blue and mounted in the stain, the organism will be 

 found to be a deeply and uniformly stained oval bacillus with one unstained 

 septum. On running a drop of acetic acid (5 per cent.) under the cover-glass 



s 



