GENERAL STAINS. 411 



haematoxyline solution from 2 minutes to an hour. They are then placed 

 in water changed repeatedly for half an hour or longer (they may remain 

 in it over night). As seen under the microscope the nuclei should be deeply 

 stained but the protoplasm should be nearly free from color. Stain in 

 cosine for i to 5 minutes; dehydrate, clear, and mount. For paraffin 

 sections this means treatment with 95 per cent., absolute and xylol, xylol, 

 and damar. For celloidin sections, 95 per cent., oil of origanum, and 

 damar. 



Methykne blue and eosine is highly recommended, especially for tissues 

 fixed in Zenker's fluid and sectioned in paraffin. Stain in a 5 or 10 per cent, 

 aqueous solution of eosine for 20 minutes or longer, overstaining the tissue 

 since the eosine is partly lost in the subsequent treatment. Wash out the 

 excess of stain in water, and transfer to Unna's alkaline methylene blue 

 diluted with three or four times as much water. Unna's blue is made by 

 dissolving i gr. of methylene blue and i gr. of potassium carbonate in 100 

 cc. oftwater. Sections should be stained in the diluted solution for 10 to 

 15 minutes. Then they are washed in water and dehydrated and decolor- 

 ized in 95 per cent, alcohol, moving the section about so that the stain may 

 be washed out evenly. The pink color returns and when, as seen under 

 the microscope, the blue is limited to the nuclei the section is cleared in 

 xylol and mounted in damar. 



Borax carmine and Lyons blue is perhaps the best general stain for 

 embryos. Dissolve 4 gr. of borax in 100 cc. of hot distilled water. When 

 cool stir in 6 gr. of the best carmine and then add 100 cc. of 70 per cent, 

 alcohol. After 24 hours, filter. The Lyons blue may be used in i per cent, 

 alcoholic solution, made with 50 per cent, or 95 per cent, alcohol. 

 Generally it is desirable to dilute it somewhat with alcohol before using. 



Before imbedding the tissue, it is stained in borax carmine from 24 to 

 48 hours, larger blocks of tissue requiring more time than small ones. 

 After being placed in water for 5 minutes (a step which some omit), the 

 tissue is transferred to acid alcohol (0.5 cc. of hydrochloric acid in 100 cc. 

 of 70 per cent, alcohol). In this the excess of stain comes out but the tissue 

 acquires a deeper color. After remaining in the acid alcohol from 15 

 minutes to an hour the tissue is washed thoroughly in 70 per cent, alcohol 

 and is imbedded and sectioned in paraffin in the ordinary way. After the 

 sections have been attached to the slide they are stained in Lyons blue, 

 rinsed in alcohol, dehydrated, cleared and mounted. 



SPECIAL STAINS. 



An attempt to present all of the important histological stains would 

 exceed the desired limits of this book. The four modifications of Golgi's 



