146 ANTHRAX 



bility of error, if the conditions restrict the examination to the 

 study of the microscopic preparations. 



Differential stain. M'Fadyean has described a peculiar 

 staining reaction, first pointed out by Heins, which he con- 

 siders of value for the microscopic diagnosis of this disease. 

 The reaction is in evidence when films of blood, exudates, or 

 tissue juice containing the bacteria are stained with a simple 

 aqueous solution of methylene blue. The method as applied 

 to blood is as follows : 



Place a drop of the blood on a clean slide. The size of 

 the drop should be about 2 mm. in diameter. It is spread 

 quickly with a platinum needle until it covers an area about 

 12 mm. in diameter. Protect from dust and allow the slide to 

 remain until all evidence of moisture has disappeared. When 

 dry, heat the preparation by lowering it film upwards into the 

 flame of a Bunsen burner or an alcohol lamp for a second. 

 Repeat this three times or until the glass is too hot to be borne 

 by the skin in the palm of the hand. Allow the slide to cool 

 and then cover the film with i per cent aqueous solution of 

 methylene blue. After a few seconds pour off the free stain 

 and wash the slide thoroughly in tap water. Dry the slide by 

 pressing it gently between two layers of bibulous paper, and 

 then more thoroughly by holding it in the current of hot air 

 above the Bunsen flame. Finally, mount in Canada balsam. 



The microscopic examinations (x 800 to 1000) will show 

 an occasional leucocyte and the anthrax bacteria. There will 

 appear no other visible formed elements. The nuclei of the 

 corpuscles generally exhibit a greenish-blue tint, the anthrax 

 rods are stained blue. The intensity of the stain depends upon 

 the length of time after death before the films were made. 

 Usually the segment character of all but the shortest rods will 

 be apparent. If they are deeply stained this is not very dis- 

 tinct. The peculiarity in the reaction lies in the color of the 

 amorphous material Tchich is present betwecJi and around the bac- 

 teria. This material presents itself under the form of coarse 

 or fine granules of a violet or reddish-purple color, which is in 

 sharp contrast to the tint of the bacteria or cell nuclei, espec- 



