Zool— Vol. I.] EISEN—PLASMOCYTES. 7 



III. Staining. 



I have tried a great variety of stains and found only a very 

 few of them useful, while some, like hematoxylin, proved 

 even injurious. I will mention the stains in order of useful- 

 ness as regards bringing out the details of the plasmocytes. 

 Toluidine. — Watery solution, not quite concentrated. I 

 found this the most useful stain, since it differentiated the 

 various spheres and zones of the plasmocyte with great pre- 

 cision, and without fail. The glass was made to swim in the 

 solution for about three minutes, then washed off with distilled 

 water and dried between pieces of blotting paper. It 

 was then brushed off with a camel's hair brush, and 

 mounted in gum-thus-xylol. The toluidine stains the grano- 

 sphere violet, the other spheres blue, excepting the hyalo- 

 sphere which remains unstained. The centrosomes stand 

 out generally quite black. I tried a number of brands of 

 thionin, but none gave satisfactory results as compared with 

 the toluidine. 



Eosin-Methyl Blue "O." — Watery solution of eosin three 

 minutes, washing with water until the stain has receded 

 from the blood serum, leaving only the cells stained. Then 

 watery methyl blue "O" for about ten seconds, washing with 

 water, and mounting as before. This method gave now and 

 then very excellent results, as the eosin has a special affinity 

 for the centrosphere and the hyalosphere, while it leaves the 

 granosphere unstained, the latter being stained by the blue 

 (fig. 49). But this method was never sure, and fre- 

 quently quite unreliable, though when it succeeded it gave 

 results not obtainable in any other way. The eosin demon- 

 strated that the centrosphere is entirely distinct from the 

 granosphere on one side, and from the somosphere on the 

 other. I found methyl blue "O" more satisfactory than 

 any other brand or variety of this stain. It stains quicker 

 and more intensely. 



Iron-HcBmatoxylin. — Another staining method which I have 

 found of interest and value is the iron-alum-hasmatoxylin 

 stain as perfected by M. Heidenhain. The method is the same 



