METHODS OF STAINING. 419 



toxylin, but that devised by Bohmer will answer all purposes, and 

 is very simple : 



1. Hsematoxylin crystals, 1 gram. 

 Absolute alcohol, 10 cc. 



2. Alum, 20 grams. 

 Distilled water, 200 cc. 



Cover the solutions and allow them to stand over night. The 

 next day mix them and allow the mixture to stand for one week 

 in a wide-mouthed bottle lightly plugged with cotton. Then filter 

 into a bottle provided with a good cork. The solution is then 

 ready for use. Nearly all solutions of alum-hsematoxylin require 

 an interval of time for " ripening," and their staining-powers 

 improve with age. 



Alum-hsematoxylin is intended for staining sections from tissues 

 that have been fixed and hardened. It is especially useful when 

 the fixing-solution employed contained chromates, but may be used 

 after almost any method of fixation, if the time of staining is of 

 the right length and the sections are previously freed from acidity 

 by thorough washing. 



If the following directions are closely adhered to, the student 

 can hardly fail to obtain good results in the use of Bohmer's 

 hsematoxylin : 



Transfer the sections from the 80 per cent, alcohol in which they 

 have been kept to a dish of distilled water. At first they will float 

 on the surface of the water ; this is a favorable moment for removing 

 all folds and wrinkles. The sections should be manipulated with 

 platinum needles, prepared by fusing a bit of platinum wire into 

 the end of a glass rod. Such needles can be cleaned by heating 

 the wire red in a flame. 



When the sections sink to the bottom of the dish of water, and 

 remain there, it may be assumed that they are free from alcohol. 



Filter about 5 cc. of the hsematoxylin into a watch-glass or butter- 

 dish and transfer the sections from the water to the dye. 



Let the sections stain for three minutes by the watch, and then 

 transfer them to a dish of distilled water. At first the sections will 

 have a reddish tint, but as the washing proceeds the color will turn 

 to a pure blue. During the washing the water should be renewed, 

 until finally it acquires no color from the sections and the latter 



