396 GENERAL MICROSCOPIC TECHNIQUE. 



washed out of the protoplasm. This usually takes twenty- 

 four hours or longer, and the acid alcohol should be changed 

 often. 



Alum carmine of Grenadier is a pure nuclear stain. It is 

 prepared as follows : 2 grammes of carmine are boiled in 5 per 

 cent, aqueous alum solution for from ten to twenty minutes. 

 On cooling, it is filtered, and 2 drops of carbolic acid added. 

 Sections are stained in this for five minutes or longer. There 

 is no danger of overstaining. Very small pieces of tissue may 

 also be stained in this fluid. 



Delafield' s Hcematoxylin. Two grammes of crystallized 

 haBmatoxylin are dissolved in 12.5 cc. of absolute alcohol ; this 

 solution is poured into 200 cc. of concentrated aqueous ammo- 

 nium-alum solution. It is left for from three to four days in 

 an open vessel in the light, and then filtered and mixed with 50 

 cc. of pure glycerin and 50 cc. of methyl alcohol. It is then 

 filtered a second time, and after standing for several weeks is 

 ready to use. It is best to use this stain very dilute; 1 or 

 2 drops in 20-50 cc. of distilled water make a solution 

 which gives a good nuclear stain in from twelve to twenty-four 

 hours. Mucus and the ground substance of hyaline cartilage 

 are also stained blue by this method. 



Hcemalum (P. Mayer) is prepared from crystallized ha3ma- 

 tein, 1 gramme of which is dissolved either in 50 cc. of 90 per 

 cent, alcohol (with warming), or in a small quantity of 

 glycerin, and mixed with 1 litre of 5 per cent, alum solution. 

 This is filtered, and is ready for use at once. It may be used 

 for sections or pieces of tissue. Sections are stained almost 

 immediately, while pieces of tissue require from twenty-four to 

 forty-eight hours. For washing out the tissues or sections, it 

 is best to use 1-2 per cent, solution of alum. This gives a 

 pure nuclear stain. 



Hcematoxylin-iron-alum (Heidenhain) is used for thin sec- 

 tions of tissue which has been hardened in corrosive sublimate. 

 These are immersed in a 1.5-4 per cent, (for centrosomes, 2.5 

 per cent.) solution of iron alum for from one-half to three 

 hours (for centrosomes, six to twelve hours). They are washed 



