LIST OF EEAGENTS, ETC. 387 



board of medium thickness cut a square wliicli does not 

 exceed a glass slide in width ; in the centre of the square 

 cut a circle whose diameter is somewhat less than that 

 of a cover-glass ; immerse the frame thus made in strong 

 alcohol for a few hours in order to kill any organisms 

 that may be attached to the pasteboard, otherwise they 

 may later become active and vitiate the culture ; when 

 ready to start the culture remove the frame from the al- 

 cohol and soak it in distilled water until thoroughly sat- 

 urated, then lay the frame on the glass slide ; in the 

 centre of the cover-slip put a drop of the culture-fluid, 

 which has previously been sterilized by boiling ; sow in 

 the drop a few of the spores which are to be cultivated ; 

 then, with the drop hanging from the under side, place 

 the cover -glass on the pasteboard frame, and keep the 

 preparation under a bell -jar with a dish of water to 

 keep the atmosphere moist and to prevent the paste- 

 board from drying ; examine the pasteboard frequently, 

 and if it shows signs of drying moisten its edges 

 with distilled water. It is convenient to keep in strong 

 alcohol a permanent supply of these frames. Moist 

 chambers may also be made by using glass rings, 

 which are furnished by dealers in microscopical sup- 

 plies. 



25. Miiller's Fluid. 



Use. — Hardening reagent. Specimens may be left in it 



from two to several weeks. 

 Preparation. — In one litre of water dissolve twenty -five 



grams of bichromate of potash and ten grams of sodium 



sulphate. 



26. Nitric Acid. 



Use. Hardens nerve, macerates muscle, and decalcifies 



osseous tissues ; colors proteids and cuticularized cell- 

 walls yellow ; swells cellulose and lignified cell-walls. 



Preparation. — Make dilute solutions from the colorless con- 

 centrated acid. Keep in glass-stoppered bottles. 



