CHAPTER XIII. 153 



best means of all.) After staining, sections may be washed out 

 either with distilled or common water. It is admirable for staining 

 in bulk. Large objects will, however, require twenty-four hours' 

 staining, and should be washed out for the same time (this should be 

 done with 1 per cent, alum solution if a sharp nuclear stain be 

 desired). All alum must be carefully washed out of the tissues 

 before mounting in balsam ; and it is well to blue the stain with 

 tap- water or otherwise, 257. The stain is generally a nuclear one ; 

 in any case such may be obtained by washing out with alum-solution. 

 Mayer's preparations have kept well in glycerin (care being taken 

 not to have it acid), also in balsam. If oil of bergamot be used for 

 clearing, it must be thoroughly removed by means of oil of turpen- 

 tine before mounting, and oil of cloves is dangerous. It is best 

 (Mayer, in litt.) to use only xylol, benzol, or chloroform, and to 

 mount in xylol-balsam or chloroform-balsam or benzol-balsam. 



Haemalum may be mixed with alum-carmine, Saurefuchsin, or 

 the like, to make a double staining mixture ; but it seems preferable 

 to use the solutions in succession. 



249. MAYER'S Acid Haemalum (Mitth. Zool. Stat. Neapel, x, 1891, 

 p. 174).- -This is ha3malum with 2 per cent, glacial acetic acid (or 

 4 per cent, common acetic acid). To be used as the last, washing 

 out with ordinary water in order to obtain a blue- violet tint of 

 stain. The solution keeps better. 



250. UNNA'S Half-ripe Constant Stock Solution (Zeit. wiss. Mik., 

 viii, 1892, p. 483). 



Hsematoxylin ....'.. 1 



Alum ........ 10 



Alcohol ....... 100 



Water 200 



Sublimed sulphur ..... 2 



If the sulphur be added to the hsematoxylin solution only when the 

 latter has become somewhat strongly blue, i.e. after two or three days' 

 time, the stage of oxidation attained by the solution will be fixeo^ for 

 some time by the sulphur, and according to Unna the solution will 

 remain " constant ' in staining power. MAYER (Mitth. Zool. Stat. 

 Neapel, xii, 1896, p. 309) finds that the sulphur process does not 

 preserve the solutions for long, whilst glycerin does. See below, 

 " GLYCHJEMALUM." 



251. MAYER'S Glychaemalum (Mitth. Zool. Stat. Neapel, xii, 1896, 

 p. 310). Hsematein (or haemateate of ammonia), 0-4 grm. (to be rubbed 

 up in a few drops of glycerin) ; alum, 5 grms. ; glycerin, 30 ; distilled 

 water, 70. The stain is not purely nuclear, but may be made so by 

 washing out with alum solution or a weak acid. The solution keeps 

 admirably. 



