EXPERIMENTS ON DYEING 325 



Treat another pair of slides in exactly the same way, with this 

 exception: after rinsing with distilled water, leave the slides for i 

 minute in the solution of hydrochloric acid in 70% alcohol. 



The results will be as follows : — 



Basic fiich sine. Chromatin and the mucosubstance of the goblet- 

 cells are strongly coloured ; the somewhat basiphil cytoplasm 

 of certain cells takes the dye feebly; nothing else coloured. 



Basic fuchsine followed by acid alcohol. There is no dye in the 

 section. 



Acid fuchsine. Chromatin and cytoplasm are both strongly 

 coloured, especially the cytoplasm at the bases of the epi- 

 thelial cells. The mucosubstance of the goblet-cells is not 

 coloured. Collagen is coloured. 



Acid fuchsine followed by acid alcohol. Same as acid fuchsine 

 alone, but even more strongly coloured. 



The effects of fixatives on the subsequent action of dyes 



Fix testes of the mouse (quartered) and small pieces of the kidney- 

 cortex of the same animal in these fluids : — 



(i) ethanol, absolute 



(2) picric acid, sat. aq., 100 ml 

 sodium chloride, 0-7 g 



(3) mercuric chloride, sat. aq. 



(4) chromium trioxide, 0-5% in 0-7% sodium chloride 



(5) formaldehyde, 4% in 0-7% sodium chloride 



(6) osmium tetroxide, 1% in 0-7% sodium chloride 



(7) potassium dichromate, i*5% in 0-7% sodium chloride 



(8) acetic acid, 5% aq. 



For a small experiment it is best to choose nos. (4) and (5) only, 

 since these will give the extremes of cytoplasmic acidophilia and 

 basiphilia respectively. No. (2) should be chosen if one wants to 

 show strong colouring of the meiotic chromosomes by acid dyes. 



Wash out in the appropriate ways; embed in paraffin; cut sec- 

 tions at 8 [i. Each slide may carry sections of material fixed in each 

 of the fixatives under test, so that subsequent treatment will be 

 identical. Sections of tissues fixed in osmium tetroxide should, 

 however, be attached to separate slides, bleached overnight in 

 sodium iodate (1% aqueous solution), and then washed in distilled 

 water before dyeing. 



X2 



