328 CYTOLOGICAL METHODS. 



693. The Mann-Kopsch Method (WEIGL, Bull. Acad. Scien. 

 Cracovie, 1912 ; HIRSCHLER, Arch. mikr. Anat. 89 ; GATENBY, 

 Journ. R. Micr. Soc., 1919). For a study of cell structure, and 

 in general cytology, the Mann-Kopsch method gives invaluable 

 results. It is an alternative to the formalin-silver nitrate tech- 

 niques of Golgi, Cajal or Da Fano, but in addition preserves fatty 

 substances. 



The Mann-Kopsch technique in itself is easy to work, but the 

 subsequent steps in staining are often extremely difficult. The 

 ordinary Kopsch technique may cause extreme shrinkage, and is 

 not generally so specific. First fix in Mann's osmo-sublimate fluid 

 ( 71) for from one quarter-hour to two or three hours or more. 

 Pieces to be fixed must be small (not exceeding a centimetre in 

 diameter) and should only be left in the osmo-sublimate long 

 enough to complete the penetration of the fluid. For an insect 

 ovary, or small invertebrate, one half -hour is sufficient ; for solid 

 tissues like nerve, longer is necessary. These times must be ascer- 

 tained experimentally. After fixation the pieces are washed in two 

 changes of distilled water for half an hour or less, according to the 

 size of the tissue and its accessibility to the water. The pieces are 

 transferred to a glass-stoppered bottle containing just enough 

 2 per cent. Os0 4 in aq. dest. to cover them. Then they are left in 

 a cupboard at room temperature, for at least ten days, and preferably 

 two weeks. Every few days the bottle should be examined to see 

 whether the Os0 4 is evaporating, or whether it has completely 

 disintegrated. Should either have happened the pieces should be 

 washed quickly in aq. dest., and new Os0 4 solution added. It 

 should be noted, however, that the osmic solution nearly always 

 becomes slightly dark, but not until it has gone black or no longer 

 smells of Os0 4 should new liquid be added. When the right period 

 has elapsed the objects are taken out of the osmic, and preferably 

 washed for several hours in running water before transference to 

 50 per cent, alcohol. They are upgraded and embedded in hard 

 paraffin. Sections to be cut from 3 to 6 /;.. They are stuck on the 

 slide with albumen and water in the usual way and dried over- 

 night. One of the slides is taken, the wax removed in xylol, and it 

 is mounted in xyol balsam. Examination of this slide will enable 

 one to ascertain to what extent the process has acted successfully. 

 In completely successful preparations the Golgi apparatus, yolk 

 and fat alone are blackened, while nuclear organs, mitochondria 

 and cytoplasm are stained in shades of yellavv and greenish brown. 

 Having studied this untreated slide, and noted the extent of the 



