320 CYTOLOGICAL METHODS. 



689. J. A. MURRAY'S Chrome-Osmic Method for Mitochondria and 

 Bacteria of Mammalian Tissue. Fix tissue in formol-salt or formol- 

 Miiller overnight. Thin slices are then placed in Muller's fluid for 

 from two to seven days, and then transferred to 2 per cent. Os0 4 

 for two days more. Wash overnight in running water, dehydrate, 

 embed in paraffin. Sections to be not more than 5 \j. thick, fixed 

 on slide, and stained in 3| per cent, iron alum at 50 C. for fifteen 

 minutes, followed by \ per cent, aqueous hsematoxylin in same way 

 and for same time. Sections should now be jet black. If such 

 sections be decolourised in the ordinary way in iron alum, both 

 mitochondria and bacteria (if present) will retain the stain, and 

 nuclei are decolourised. 



If such sections are decolourised in 05 per cent. HC1 in 7.0 per 

 cent, alcohol, the mitochondria give up the lake and the bacteria 

 remain deeply stained. At the same time the details of the nuclei 

 are sharply stained. Wash sections for twenty minutes in tap- water, 

 counterstain in Van Gieson, mount in balsam (Report Imp. Cancel' 

 Research Bureau, 1919). 



690. Double-Staining in Hrematoxylin and Acid Fuchsin. It is well 

 known that different cell elements have varying powers of resisting 

 decolourisation or differentiation after iron alum or such hsematoxylin' 

 stains. Thus in a hermaphrodite gonad or during fertilisation it is 

 sometimes noticed that the mitochondria of the egg hold the haematin 

 lake much faster than those of the sparm or spermatogenesis stages. It 

 is possible in certain cases to make use of this fact for studying differen- 

 tially cell granules, etc. 



Fix tissue by some prolonged mordanting method, such as that of 

 Champy-Kull, or Regaud. Wash out well in running water and prepare 

 thin paraffin sections. Stain by some intense hseinatoxylin method, 

 such as that of Bend a or Heidenhain ; differentiate the cell element 

 which you wish to b3 stained subsequently a red colour, till it looks 

 pale greyish under the microscope : wash well in water, and counter - 

 stain in Altmann's acid fuchsin. Extract the fuchsin to the right stage 

 in 95 p?r cent, alcohol, quickly dehydrate and clear in xylol ; mount in 

 balsam. If necessary, aft3r staining in acid fuchsin, you may apply 

 the picric acid of Altmann's method ( 680), but this necessitates under- 

 differentiation in the iron alum. 



I have found that after staining in the acid fuchsiu you may differen- 

 tiate partly in aurantia as for the Kull method ( 681). 



A method to be tried only by experienced cytologists. The difficulty 

 is to differentiate the haematoxjdin just to the right stage, and to avoid 

 washing away the acid fuchsin (GATEXBY, Jouni. Roy. Micr. Soc., 

 1919 ; HANS HELD, Arcli. f. mikr. Anat., Bd. Ixxxix). 



691. On Post-Chroming and Post-Osmication in General. By 



soaking tissues in K 2 Cr 2 7 , with or without Cr0 3 , one produces 



