CHAPTER XIII. 



distilled or common water. It is admirable for staining in 

 bulk. Large objects will, however, require twenty-four 

 hours 3 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 care- 

 fully 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 turpentine before mounting, and oil of cloves 

 is dangerous. It is best (Mayer, in Hit.) 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 hasmalum 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 (Zeii. wiss. Mik., 

 viii, 1892, p. 483). 



Hseinatoxylin ........ 1 



Alum ......... 10 



Alcohol ......... 100 



Water ......... 200 



Sublimed sulphur ....... 2 



If the sulphur be added to the liaBmatoxylin 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 J)e fixed 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 telow, " 



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

 p. 310). Ha?matein (or hsomateate of ammonia) 0'4 grm. (to be rubbed 

 u]i 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 



