336 CYTOLOGICAL METHODS. 



a few drops are taken from it and added to a beaker of 

 distilled water until there is obtained the crimson tint of the 

 first test-beaker. Addition of acid should then cease, and 

 the staining bath is ready. If the preparations should not 

 turn out quite satisfactory a small further quantity of acid 

 may be added. 



Before staining, sections should be treated for a couple 

 of hours with O'l per cent, acetic acid, then for ten to 

 fifteen minutes with officinal tincture of iodine, and be rinsed 

 with alcohol before bringing into the stain, in which they 

 should remain for twelve to eighteen hours. The treatment 

 with acid is necessary in order to ensure having the sec- 

 tions acid on mounting in balsam. The primary object of the 

 iodine is to remove any sublimate from the preparations 

 (Heidenhain's descriptions refer to sublimate objects, but 

 Ehrlich-Biondi mixture will work with chrome objects) ; but 

 it also enhances the power of staining of the chromatin with 

 methyl green, and produces a more selective staining of 

 protoplasmic elements. 



Instead of acidifying with acetic acid, the mixture may be 

 modified by increasing the proportion of acid fuchsin, a sug- 

 gestion which is, I gather, also due to HEIDENHAIN (I do not 

 know whether it has been published). Dr. Griibler has sent 

 me a mixture of the three colours in the dry state in such pro- 

 portions that you have only to dissolve 0'4 grin, of the mixture 

 in 100 c.c. of water, and add 7 c.c. of a 0'5 per cent, solution 

 of Sauref uchsin . I greatly regret that I am unable to make 

 trial of this preparation before going to press. 



BENDA ( Verh. ph ysiol. Ges. zu Berlin, Dec. 18th, 1891, Nos. 4 

 u. 5 ; see also Zeit.f. WISH. Mik., viii, 4, 1892, p. 516) proceeded 

 as follows (testes of Mammalia) : Sections stained for twenty- 

 four hours in anilin- water safranin solution, then for about 

 half a minute in a solution of ! 5 grm. " Lichtgrim F. S." or 

 Saureviolett (Griibler) in 200 c.c. of alcohol, dehydrated, and 

 mounted in balsam. Chromatin red, archiplasma bright green 

 (or violet), centrosomata and " Spitzenknopf " (of spermato- 

 zoa) sometimes green, sometimes red. The chroinatoid 

 " Nebenkorper " of HERMANN stains red. 



The achromatic structures of the ova of Axc<tri* are best 

 demonstrated, according to VAN BENEDEN and NEYT (None. 

 liech. sur la Fecund. < t La Uiv. mitorique), by fixing with acetic 



