STAINING AND MOUNTING PARAFFIN SECTIONS I93 



5. Wash in running water for ten minutes or longer. This 

 removes the stain from the tissues before decolorizing the 

 bacteria, and a fairly differentiated specimen may be obtained if 

 the processes of staining and washing are carried out for suitable 

 lengths of time. 



Unna's polychrome methylene blue may be used in a similar 

 manner, and gives even better results. The staining should be 

 continued for about ten minutes, and decolorization effected by 

 very short immersion in dilute acetic acid (about ^ per cent.), 

 followed by a good washing in pure water. 



6. Remove as much water from the section as you can without 

 actually drying it by the cautious use of clean blotting-paper. 

 Then apply aniline oil until the section becomes perfectly trans- 

 lucent. Aniline oil mixes with water on the one hand and xylol 

 on the other, and can be used for dehydration just as alcohol 

 was ; the process is slower, and several lots of the oil must be 

 used. 



7. Wash off all the aniline oil by successive applications of 

 xylol. The permanence of the preparation will depend on the 

 thoroughness with which this step is carried out. 



8. Balsam and a cover-glass. 



IV. Staining sections to demonstrate the tubercle bacillus ; 

 applicable to the leprosy bacillus also. 

 ^ I, 2 , 3. Xylol, alcohol, and water, as before. 



4. Carbol fuchsin heated until the steam rises for five minutes 

 or longer, care being taken that the section does not dry up. Or 

 the slide may be immersed in the stain and kept in a warm place 

 for twenty-four hours. 



5. Dilute sulphuric acid until only a faint pink tinge appears 

 after washing. This will generally require an immersion of ten 

 minutes or more. 



6. Methylene blue for three or four minutes. Some of the 

 stain comes out in the alcohol, so that the section must be stained 

 more deeply than' will be required ultimately. 



7. Rinse off the blue stain in water, and then remove the greater 

 part of the latter with blotting-paper ; this is to render the dehy- 

 dration more rapid. '' 



8. Absolute alcohol, two lots in rapid succession. 

 g. Xylol. 



10. Balsam and a cover-glass. 



13 



