11 8 PRACTICAL BACTERIOLOGY. 



staining. Ziehl's carbolic fuchsine also yields very 

 good results with methylene blue, and may be recom- 

 mended for examinations of sputum. In this case 

 decolourisation is effected in the same way as when the 

 aniline water staining solutions are used. 



If a preparation of sputum be put into simple 

 aqueous staining solutions, and then rinsed with water, 

 the tubercle bacilli are unstained, and are therefore 

 not to be seen, whilst the other objects, the elements 

 of the animal tissue, and the other bacteria are 

 coloured. Tubercle bacilli are to be distinguished 

 from nearly all other bacteria by these characteristics, 

 namely, that on the one hand, it is so diflBcult to stain 

 them ; and on the other, that it is even more difficult to 

 decolourise them. The leprosy bacilli alone resemble ^ 

 them in these particulars, but they are hardly ever 

 met with in Germany, and, moreover, are not likely 

 to be found in sputum. 



It is absolutely necessary to keep strictly to one of 

 the methods described above, if the student wishes to 

 make himself fully acquainted, with the peculiarities 

 of the tubercle bacillus, so that he may be certain to 

 discover and recognise it under all conditions. He is 



' Amongst those forms which have been less frequently 

 and fully examined are found the syphilis bacillus of Lust- 

 garten, and the Smegma bacillus, both of which behave in a 

 similar manner towards staining solutions ; and also the 

 bacillus of fowls' tuberculosis, which apparently may be dis- 

 tinguished from the trtie tubercle bacillus. 



