154 



stain for 24 to 48 hours, are then rinsed in distilled water, 

 and placed in an acid alcohol wash 



Alcohol (70%} 100 c. c. 



and hydrochloric acid 3 to 5 drops, 



for 3 to 6 hours. They are then washed in flowing water 

 for 1 to 2 hours, dehydrated, and embedded in paraffin or 

 celloidin. Embryos are very well stained by this method. 



Heidenhain's Haematoxylin Solution. 



Tissues need to be hardened in alcohol, and stained 

 en masse. Gland tissues are well stained by this method. 

 Small pieces of the tissue are placed in a 1% aqueous 

 solution of hsematoxylin crystals, where they remain for 

 8 to 12 hours. They are then transferred to a 1% aqueous 

 solution of bichromate of potash for 12 to 18 hours ; in 

 this solution the tissues become jet black. Embed in 

 paraffin. 



Heidenhain's Iron-Lack-Haematoxylin Solution. 



The tissues are to be hardened in alcohol, mercuric chlo- 

 ride, Flemming's or Hermann's solution, or in the osmium, 

 platinum chloride, and mercuric chloride mixture suggested 

 by the author. They are then embedded in paraffin. The 

 sections must be cut very thin. These are fixed to cover 

 glasses with albumen fixative, which is best done by 

 floating the sections on warm distilled water, and drawing 

 them upon a cover smeared with a thin layer of the fixa- 

 tive. 



The steps are as follows : 



Remove paraffin from sections, 



4 



Place cover glass with sections fixed to it in a 3% aqueous 

 solution of ammonium sulphate of iron. for. I to 3 hours.: 



V 



Rinse in distilled water for a few minutes. 



I 



Place sections into a saturated aqueous solution of hsema- 

 toxylin crystals for 1 to 3 hours. 



; 



Rinse in distilled water. 



