RECIPES, FORMULAE AND USEFUL HINTS. 137 



Eosin andfuschine (aniline colors) are used in a two per cent, aque- 

 ous solution but have a tendency to stain all parts equally. The method 

 of operation is similar to that with carmine. 



Nitrate of silver is used for differentiating the walls of cells. The ob- 

 ject is placed for a few moments in a solution made of nitrate of silver, 

 one part, distilled water, 500 parts, then washed in distilled water and 

 exposed to the direct rays of the sun. It is then mounted as may be 

 desired and shows the cell walls black, and in many cases this is the 

 only way in which they can be seen at all. 



Osmic acid, in one-tenth per cent, solution, is useful fo studying 

 nerves and fatty tissues as it stains them black. Great care should be 

 taken in using osmic acid as it is one of the most poisonous substances 

 known, and its vapor badly affects the eyes and nasal passages. 



Chloride of gold is also of value in studying the histology of the 

 nerves. Sections are first placed from five to seven minutes in a one 

 half per cent, solution of the chloride, then soaked in distilled water 

 several hours, next placed in water acidulated with lactic acid to reduce 

 the chloride, and after the proper color (a dark purple) is obtained, the 

 specimens are washed with distilled water and soaked in alcohol and 

 mounted as may be desired. 



Moleschott's acetic acid and alcohol (strong). 



Strong acetic acid (sp. gr. 1 . 070) i part. 



Strong alcohol I part. 



Distilled water 2 parts. 



This hardens many organs, makes connective tissue transparent and 

 renders albumen distinct. 



Moleschott's acetic acid (weak). 



Acetic acid (sp. gr. 1.070) I part. 



Alcohol 25 parts. 



Distilled water 50 parts. 



This is better for delicate tissues than the strong. Besides rendering 

 connective tissue transparent, acetic acid renders the nuclei of cells 

 more plainly visible. When a one per cent, solution of acetic acid is 



