STAINING, PRACTICAL AND THEORETICAL 



i8. Dip the section for one second in the silver solution (F). 



19. Immediately reduce in the gelatine-formalin (solution H), 

 omitting the pre-washing in solution G. 



Notes: 



(i) If necessary this step can be repeated, 

 (ii) Connective tissue fibres can be fully stained by this pro- 

 cedure but the cells and some tissues may remain unstained. 



20. If the staining is too intense, decolorize in the iron alum 

 (solution C). 



Note: If the decolorization is carried too far, the desired depth 

 of staining can be achieved again by repeating steps 12 to 15, 

 but it is best to avoid prolonged soaking in the iron alum as this 

 causes the staining to lose its precision. 



*2i. Tone in gold chloride (solution I) for five minutes or more. 

 *22. Fix in the sodium thiosulphate (solution J) for one to two 

 minutes. 



23. Counterstain in eosin or erythrosin (solution K), if desired. 



Results: 



Successful preparations show brilliant and complete staining: 

 even the finest reticulum fibres are stained black, and the col- 

 lagenous fibres light brown. When the staining of cells is achieved 

 and the gold toning omitted, the cytoplasm is stained in various 

 shades of yellow and the nuclei are black. In some cases only 

 the cytoplasm is stained, with the nuclei barely visible. The 

 background is transparent and without precipitates. 



Notes: 



(a) The original author (Lascano) states that this method, 

 which is also applicable to frozen sections, can be applied to 

 sections attached to slides but the results are less satisfactory, the 

 structures possessing less brilliancy with little if any colour 

 differentiation. 



(b) The author states that there are no fixed rules or periods of 

 time in his technique, described above, which may be varied 

 with each kind of tissue. Sections must be stained one by one, 

 and checked during the process by microscopic examination, 



* Steps 21 and 22 are optional. 



412 



