NEW METHODS OF USING THE ANILINE DYES. 411 



geneous masses plugging the smaller blood-vessels and expand- 

 ing the capillaries. There was absolutely nothing to show 

 whether or not these were masses of bacteria. But after I 

 had exposed the mounted sections to sunlight for a day, the 

 Spiller's purple present in the interspaces between the bacilli 

 was completely destroyed, and the masses that before seemed 

 to be amorphous were now seen to consist of clusters of minute 

 bacilli marked out with perfect distinctness. 



Some sections stained by the method last described were 

 exposed to ten days' sunlight during the hottest part of last 

 July, without appreciable change, and they still show every- 

 where the bacilli of a dark blue black tint, though the back- 

 ground of the tissue has become so bleached as to be nearly 

 invisible. This permanency of the stain produced by methyl 

 blue and fuchsin in combination is remarkable, when it is 

 remembered that manufacturers regard a dye as '' fast to light " 

 when a tissue stained by it is unchanged by three hours' 

 exposure. 



These methods of staining are generally inapplicable to 

 coverslip specimens. But preparations of anthrax blood or 

 pneumonia sputum, very excellent for demonstration purposes, 

 can be made as follows : 



The films are stained with methyl blue or Spiller's purple, 

 washed and dried as usual, and then a drop of eosin dissolved 

 in oil of cloves is placed on them for a few minutes ; this is 

 then washed off with clove oil and benzine mixture. This 

 again is removed with benzine and the coverslips are then 

 mounted. Bacteria are seen to be stained blue, red blood- 

 corpuscles are red, pus-cells or leucocytes generally have purple 

 nuclei, and the background has a pinkish tint. 



The method of staining by means of eosin and methyl blue 

 gives very good results from a histological point of view, but 

 will only succeed with bacteria that are easy to stain. 



The methods of double treatment with fuchsin and Spiller's 

 purple are successful with nearly all bacteria. 



Tubercle bacilli, however, cannot be satisfactorily stained 

 by any of these methods. 



