STAINING AND MOUNTING PARAFFIN SECTIONS 22/ 



This method of staining is very easy of application, and 

 the results are exceedingly beautiful. Bacteria which take 

 the stain are coloured blue or violet, and actively dividing 

 nuclei and keratin are stained in the same way, while all other 

 structures are stained pink. 



III. Method for bacteria which do not stain by Gram's 

 method, suitable for sections of typhoid ulcers, lymphatic 

 glands containing plague bacilli, etc. 



The problem before us in this case is not at all easy of 

 solution. In the first place, the stains which colour the bac- 

 teria also colour the tissues, especially the cell nuclei; the 

 bacteria are easy to stain, but it is difficult to stain a section 

 in which there is good differentiation. In the second place, 

 the stains which are used for bacteria are all soluble in 

 alcohol : but alcohol is used to dehydrate the sections. The 

 following method will be found to serve fairly well in most 

 cases, though it requires a certain amount of practice for its 

 successful accomplishment : 



i, 2, and 3. Xylol, alcohol, and water, as before. 



4. Stain in carbol thionin for ten minutes or a quarter of 

 an hour. 



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 blot- 

 ting-paper. Then apply aniline oil until the section becomes 

 perfectly translucent. Aniline oil mixes with water on the 

 one hand and xylol on the other, and can be used for dehydra- 

 tion 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. 



