STAINING AND MOUNTING PARAFFIN SECTIONS igi 



water. It will hasten the process to rinse them in a very dilute 

 solution of ammonia, or, best of all, a saturated solution of lithium 

 carbonate. 



6. Stain in watery eosin for a minute or so. This is the 

 counterstain. The hasmatin will stair> all nuclei blue, but will 

 scarcely tinge anything else ; the eosin is added to stain other 

 structures a pale pink, and thus make them more visible. It 

 stains almost instantaneously. 



7. Wash off the eosin under the tap. 



The sections are now stained. But they are opaque, and not 

 in a suitable condition to be examined under the microscope, and 

 are to be rendered transparent by being mounted in balsam. 

 Now this cannot be done in the same way as was used in the 

 mounting of films, for the drying would cause the sections to 

 shrivel and obscure their structure. The water is to be removed, 

 it is true, but by the use of absolute alcohol ; at least two lots 

 should be used, and the slide rocked from time to time. Then 

 the alcohol (which will not mix with balsam) is to be removed by 

 the use of xylol, balsam added, and the section covered with a 

 cover-glass. The remaining steps are therefore : 



8. Absolute alcohol, two lots (to dehydrate). 



9. Xylol, two lots (to render the section permeable to balsam). 



10. Balsam and a cover-glass. 



The last three steps are practically the same as the first three, 

 but in the reversed order, and similar phenomena are seen. The 

 section is opaque whilst wetted with the alcohol, and becomes 

 transparent when the xylol is added, and this transparency is the 

 proof that the steps have been carried out properly. If the 

 section looks opaque when held against a perfectly dark back- 

 ground, an additional dose of alcohol must be used, and the xylol 

 applied again. 



11. Gram's method as applied to sections, suitable for sections 

 of diphtheritic membrane, organs containing anthrax bacilli, 

 streptococci, staphylococci, etc. : 



1. Xylol, two lots. 



2. Absolute alcohol, two lots. 



3. Water. 



These steps are- always the same with paraffin sections, no 

 matter what stains are to be used subsequently. 



4. Aniline gentian violet — five minutes. 



c Gram's iodine solution — three minutes or more. 



