SPECIAL METHODS. l8l 



few days and is filtered again. Since the method of pre- 

 paring it is somewhat complicated, many will prefer to- 

 obtain it ready prepared from a chemist (e.g., from Dr. G. 

 Griibler, Leipzig). 



315. The so-called Bohmers hcematoxylin is also very useful. 

 It is prepared from a concentrated alcoholic solution of 

 haematoxylin which, contains .35 gram of haematoxylin to ia 

 grams of alcohol and will keep indefinitely. A few drops of 

 this are added to a solution of .10 gram of alum in 30 ccm. 

 of water. This mixture is allowed to stand for a few days, 

 and is filtered before use. 



P. Mayer (III) obtained an haematoxylin solution that may 

 be used at once by dissolving i gram of hcematein or hamate'in- 

 ammonia in 50 ccm. of 90$ alcohol by warming, and then 

 adding the whole to a solution of 50 grams of alum in a litre 

 of water. This solution may be diluted with distilled water 

 for staining, as desired. 



Concerning the other solutions of haematoxylin which may- 

 be valuable in special cases, and may in part be obtained 

 ready for use from various chemists, reference may be had 

 to the compilation of Gierke (I, 32-35). 



316. If it is desired to stain sections with haematoxylin^ 

 they are best placed in a very dilute solution and left in it 

 for a considerable time (i to 24 hours). With alcoholic 

 material it is advisable to place it in water for a short time 

 before staining it, as otherwise precipitates are readily 

 formed. 



Beautifully differentiated stainings may usually be ob- 

 tained by staining sections too deeply (" overstaining") and 

 then washing them out with a suitable fluid. With an 

 haematoxylin stain, a solution of alum (about 2%) is com- 

 monly best ; but it must be thoroughly washed out before 

 the transfer to alcohol or to Canada balsam, as otherwise 

 alum crystals will be formed in the preparation. 



Acid alcohol has also been recommended for washing out 

 haematoxylin ; but the acid must be completely removed 

 with pure alcohol before the final mounting. 



Very good nuclear staining may often be obtained by 



