CHAEACTERS OF THE B. PEST IS 17 



between blood corpuscles and connective tissues — pink, — 

 bacteria and nuclei — blue, — is very striking. 



I have extensively used this mixture both for film 

 specimens of tissues and for sections for the last thirteen 

 years, and do not consider any other mixture comparable 

 to it in effecting strong contrasts and bringing out the 

 different parts of the tissues, bacteria, fungi, etc., with 

 admirable distinctness. 



(6) The ordinary Ziehl's carbolfuchsin is used ; a 

 small quantity of it is diluted with an equal volume of 

 absolute alcohol ; over this fluid in a watch-glass is placed 

 the cover film specimen, having previously been kept for 

 half a minute in absolute alcohol as above ; the film 

 specimen remains in the dilute fuchsin for ^-f-1 minute, 

 then it is well washed in tap water, then in distilled 

 water, dried, and mounted in balsam. The plague bacilli 

 both of tissues and of recent culture show polar staining 

 very distinctly ; but it is essential that the films after 

 staining should be well washed — that is, until no further 

 discharge to the water of pink colour is noticed. 



These two methods suffice for all purposes ; in fact, the 

 first-named double stain will practically be found quite 

 efficient. B. pestis do not retain the stain after Gram 

 solution, that is they are Gram-negative, and share there- 

 fore this character with the microbes of the coli-typhoid 

 and with those of the proteus group ; it is important to 

 remember this, because it is just with these two groups 

 (B. coli, B. Gaertner, proteus) that error in diagnosis may 

 be, and as a matter of fact has been, in some instances, 

 committed. Judging from the accounts given by different 

 observers, "Gram staining" appears as a sort of variable 

 quantity ; I will therefore state here the manner which 



C 



