CH. X] REAGENTS AND THEIR PREPARATION 355 



561. Elastic stain. For staining elastic substance the resorcin- 

 basic-fuchsin-iron-chlorid of Weigert is available. The stain is 

 prepared as follows. 



Basic fuchsin 2 grams. Resorcin 4 grams. Water 200 cc. Boil 

 for several minutes (5 to 10). Add to the boiling mixture 25 cc. of a 

 30% aqueous solution of chlorid of iron (FeCle). Boil for 3 to 10 

 minutes; then add a saturated solution of the iron chlorid until the 

 color is all precipitated. Try the liquid occasionally by letting a few 

 drops run down the side of the glass beaker used for the boiling. 

 If the color is precipitated it appears as fine granules and the liquid 

 is almost uncolored or slightly yellow 7 . 



Allow the liquid to cool. If there is plenty of time let it stand over 

 night. Then either pour off the supernatant liquid or if the precipi- 

 tate has not settled filter through filter paper. Then either scrape 

 off the precipitate from the filter paper or cut off the lower end of the 

 filter containing the precipitate and put it in the beaker. Add 200 cc. 

 of 95 % alcohol and heat over a water bath till the alcohol boils. 

 Continue the boiling 5 minutes or more and stir up the filter paper 

 so that all the precipitate may be dissolved. After boiling 5 minutes 

 or more filter the hot alcoholic solution into a warmed bottle. After 

 this alcoholic solution is cool add 5 cc. of strong hydrochloric acid. 



Stain sections in this solution i hour, sometimes less. Wash off 

 the stain with 95 % alcohol. 



This works well on sections by the paraffin or the collodion method 

 and for tissues hardened in any manner. 



562. Eosin. This is used mostly as a contrast stain with hema- 

 toxylin, which is almost a purely nuclear stain. It serves to stain 

 the cell-body, ground substance, etc., which would be too transparent 

 and invisible with hematoxylin alone. If eosin is used alone it gives 

 a decided color to the tissue and thus aids in its study. Eosin is 

 used in alcoholic and in aqueous solutions. A very satisfactory stain 

 is made as follows: 50 cc. of water and 50 cc. of 95% alcohol are 

 mixed and xV of a gram of dry eosin added. \ % aqueous eosin is also 

 good. 



563. Eosin in 95 per cent alcohol. For staining embryos and 

 tissues so that the tissue in the ribbons of sections may be easily seen 



