CHAPTER XXVI. 327 



stainaV-e compounds of cell proteins and lipoids which are not easily 

 dissolved out by alcohol and a clearing oil. One may fix in almost any 

 mixture not containing alcohol, chloroform and acetic acid. Wash 

 the tissue in aq. dest. for a short time (say half an hour or less), cut 

 into small pieces, and transfer to 3 per cent, potassium bichromate 

 for several days, and then to 1 or 2 per cent. Os0 4 for a day. Wash 

 under tap overnight and stain in Heidenhain or an Aitmann. Thus 

 tissues or embryos fixed in special formol-chrome, corrosive formol, 

 chrome-corrosive, and other mixtures which one has found most 

 suitable for one's purpose, may be post-chromed, or post-osmicated 

 as well. Schridde's and Murray's methods (above) include both 

 post-chroming and post-osmication. 



692. KOPSCH'S Osmium Tetroxide Method (Sitzungberg. d. k. 



preuss. Akad. d. Wiss. zu Berlin). Osmium tetroxide solution will 

 fix both fats and lipoids, and proteid substances. As has been 

 mentioned above, the various cell inclusions, such as mitochondria, 

 Golgi apparatus, yolk and fat, are nearly always mixtures of different 

 quantities of several definite substances, and consequently will 

 reduce the osmic solution in varying degrees of intensity. Kopsch 

 methods are somewhat capricious, but one gets results unequalled 

 by other methods ; for chrome-osmium, or chrome-formol, followed 

 by iron hsematoxylin, or Aitmann, generally will not demonstrate 

 the Golgi apparatus (except in male germ-cells), while the Kopsch 

 methods preserve and demonstrate Golgi apparatus, mitochondria, 

 yolk, fat and chromatin structures, and occasionally neurofibrils 

 of embryos. 



For this method dissect out organs, and cut tissue into small 

 pieces ; dip these quickly into aq. dest. to remove blood or cell 

 detritus from surface, and then transfer to a small glass-stoppered 

 or glass-covered capsule of 2 per cent. Os0 4 . Leave in a darkened 

 cupboard for two weeks (fourteen days) at room tempera- 

 ture. Wash in running water for several hours, dehydrate, 

 embed in hard wax ; section about 3 p.. Mount unstained, or 

 stain chromatin in safranin or methyl-blue eosin. Unsaturated 

 fats black, others yellowish, Golgi apparatus, and sometimes 

 mitochondria, black. 



This method succeeds for mollusc and many invertebrate and 

 vertebrate tissues, but the following Mann-Kopsch method is 

 generally superior. Note that a trace of chromic acid, potassium 

 bichromate, or platinum chloride, in the Os0 4 solution will inhibit 

 the blackening of the Golgi apparatus, but not of fat. See also 

 776. 



