CHAPTER XIV. 165 



Series of sections on slides are conveniently cleared by pouring 

 the clearing agent over them. 



After clearing you may either mount at once in damar or balsam, 

 or stop the extraction of the colour, if clove oil have been used, by 

 putting the sections into some medium that does not affect the stain 

 (xylol, cedar oil, etc.). Chloroform should be avoided, either as a 

 clearer or as the menstruum for the mounting medium. 



283. General Results. The results depend in great measure on 

 the previous treatment of the tissues. If you have given them a 

 prolonged fixation in Flemming's strong chromo-aceto-osmic mixture, 

 and have differentiated after staining with acid alcohol and cleared 

 with clove oil, you will get, with some special exceptions, nothing 

 stained but nucleoli and the chromatin of dividing nuclei, that of 

 resting nuclei remaining unstained. If you have given a lighter 

 fixation, with Flemming's weak mixture or some other fixing agent 

 not specially inimical to staining, and have differentiated after 

 staining with neutral alcohol, you will get the chromatin of resting 

 nuclei stained as well. Either process may also stain mucin, the 

 ground-substance of connective tissues (especially cartilage), the 

 bodies of Nissl in nerve-cells, and the yolk of ova. 



284. HENNEGUY'S Permanganate Method (Journ. de VAnat. et de la 

 Pkysiol., xxvii, 1891, p. 397). Sections are treated for five minutes with 

 1 per cent, solution of permanganate of potassium. They are then 

 washed with water and stained (for about half the time that would have 

 been taken if they had not been mordanted with the permanganate) in 

 safranin, rubin, gentian violet, vesuvin, or the like, and are differentiated 

 with alcohol, followed by clove oil in the usual way. 



The mordanting action of the permanganate is so energetic that if it 

 has been overmuch prolonged before staining with safranin, or, still 

 more, with rubin, it becomes almost impossible to differentiate the 

 sections properly ; it may be necessary to leave them for a month or 

 more in clove oil. 



285. OHLMACHER/S Formaldehyde Process (Medical News, February 

 16th, 1895). Ohlmacher states that formaldehyde is a powerful 

 mordant for tar colours. Tissues may either be mordanted separately 

 by treatment for a short time (one minute is enough for cover -glass 

 preparations) with a 2 per cent, to 4 per cent, formalin solution ; or the 

 formalin may be combined with the stain. One grm. of fuchsin or 

 methylen blue dissolved in 10 c.c. of absolute alcohol may be added to 

 100 c.c. of 4 per cent, formalin solution. Sections are said to stain in 

 half a minute and to resist alcohol much more than is the case with 

 those treated by the usual solutions. 



286. Safranin. One of the most important of these stains, on 

 account of its power, brilliancy, and permanence in balsam, and the 



