n8 ELEMENTARY TECHNOLOGY. 



strong alcohol till needed for section. For the freezing micro- 

 tome the gum process is best 



6. Increasing transparency of tissues. 



1. Impregnating with strongly refractive fluids, as glycerine, 

 turpentine, clove oil, Canada balsam or Damar varnish. 



2. Partially or completely dissolving some elements of the 

 tissues so as to permit others to be seen. Acetic acid, or 

 caustic potass, or soda for dissolving soft albuminoid elements- 

 Glycerine and caustics for wet preparations, clove oil or tur- 

 pentine for dry or alcoholic. 



7. Sta in ing t issues . 



1. The stain may be uniform and be serviceable by render- 

 ing very transparent parts more evident. 



2. Some parts may be more affected than others and so 

 differentiate elements. Thus the nucleus is most deeply 

 tinged by' carmine or magenta, epithelial cement by silver 

 nitrate, and nerve fibrils by gold chloride. 



From a large list the following most useful. Best procured 

 in solution from opticians. 



Carmine. Beale's weak and strong fluids, or solution of 

 alum carmine. 



Picro-carmine. For double stain. Nuclei, etc., red; muscle, 

 epithelium, etc., yellow. 



Logwood. Violet. 



Magenta. For rapid stain. One gr. to gi water and 3 i al- 

 cohol. 



Nit. silver. ^ per cent solution. Tissue afterwards ex- 

 posed to light. 



Gold chloride. ^ per cent solution. After soaking tissue 

 in it 15 minutes to 2 hours, place it in I to 2 per cent acetic 

 or lactic acid and expose to daylight till a gray or violet tint 

 appears. 



For staining bacteria various methods are used, as different 

 bacteria stain differently. It is more difficult to stain them in 

 tissue sections than in fluids. Watery solutions of stain must 

 be used and sections cleared up after alcohol with cedar oil o r 

 xylol and not with oil of cloves. 



