330 CYTOLOGICAL METHODS. 



brought down to distilled water, and cautiously treated in a '5 

 to -125 per cent, solution of potassium permanganate, in order 

 to recover the staining properties of the tissue. A very short time 

 suffices. Wash in water ; then stain ( 680). 



An important part of the technique is to ascertain the optimum 

 length of time to leave the tissue in the Mann's fluid. Examples 

 are as follows : 



(1) Saccocirrus (entire) overnight in Mann. 



(2) Cavia testis about five hours. 



(3) Chick embryos about one quarter-hour. 



The Mann-Kopsch technique can be used in combination with the 

 Kull staining method ( 681). We find that the cells are rather 

 liable to overstain in the toluidin blue, which must be left on for a 

 very short time. 



Explanation. Mann's osmo- sublimate fixes the cells successfully, 

 bscause the HgCl 2 aids penetration and the Os0 4 is not so strong as to 

 cause shrinkage. Thus, before the tissue is transferred to the Kopsch 

 fluid (Os0 4 of 2 per cent.), a complete fixation has taken place and the 

 distorting effect of the strong Os0 4 is avoided. Left for two weeks, the 

 lipoid materials which partly form the substance oi the Golgi apparatus, 

 the unsaturated fats, and the special lipoids of the mitochondria, aie all 

 able to reduce the Os0 4 in varying degrees. The subsequent treatment 

 of the sections by turpentine (oxidiser) introduces a further differentia- 

 tion, and so the various inclusions can be distinguished. The acid fuchsin 

 stains presumably the lipoid content of the mitochondria. Sae also 768. 



695. Osmic Vapour Method (W. CRAMER, Imp. Cancer Research 

 Fund Report, 1919). Choose a small glass-stoppered bottle, and 

 place a piece of wide glass tube open at both ends, in the bottom. 

 Arrange a piece of gauze over the top of the inner tube. Add 

 some 2 per cent. Os0 4 to the outer vessel. Objects to be fixed 

 by the osmic vapour are placed on the gauze. All the surrounding 

 (fatty) tissue should be removed from the organ or material to be 

 treated ; if too dry the outside of the material should be slightly 

 wetted. 



The bottle, with object suspended in the Os 4 vapour, is kept at 

 temperature of 40 C. for one and a half hours. Removed from 

 bottle, the tissue is placed in 50 per cent, alcohol and upgraded and 

 embedded in paraffin. Cut sections, mount in balsam without 

 staining. Such wax sections may be treated in 10 per cent, hydrogen 

 peroxide in 80 per cent, alcohol for two hours, after which they may 

 be stained in ordinary methods (e.g. iron hsematoxylin). 



GATENBY (Quart. Journ. Micr. Set., 1920) suggests two modifications. 

 (a) Fix as above for one and a half hours, and then transfer to 2 per 



