1899] MICROSCOPICAL JOURNAL 313 



gum may collect around the margin, but by properly regu- 

 lating- the quantity originally added, enough will remain 

 under the larger grains to hold them so fast that they will 

 not be squeezed out in the excess of balsam. 



Ink. — Dr. Marpmann, of Leipsic, has recently publish- 

 ed the results of his microscopical examinations of sixty- 

 seven samples of ink used in schools. Most of these inks 

 were made with gall nuts, and contained saprophytes, bac- 

 teria, and micrococci. Nigrosin ink taken from a freshly 

 opened bottle was found to contain both saprophytes and 

 bacteria. Red and blue inks also yielded numerous bacte- 

 ria. In two instances he succeeded in cultivating from ni- 

 grosin ink a bacillus which proved fatal to mice in four 

 days. This ink had stood in an open bottle for three months, 

 and the inference to be drawn from the enquiry is that 

 ink used in schools should always be kept covered when 

 not in use. 



Stain. — According to Nocht, the success of the nucleus 

 stain of Romanowsky, a mixture of eosin and methylene 

 blue, depends upon the presence of certain impurities in 

 the methylene blue. To obtairtfthe best results the use of 

 polychromic methylene blue is suggested, as the essentials 

 for the formation of the nuclear stain are more frequently 

 met with in this than in any other. Before using, its alka- 

 line reaction should be neutralized with acetic acid, and the 

 solution should then' be'' mixed with ordinary methylene 

 blue until it fs-clear and blue. Finally dilute the fluid with 

 a one per cent aqueous solution until a reddish tinge is ap- 

 parent near the edges. • Macerate the preparations in this 

 for some time, and if too much stain is taken up decolor- 

 ize with dilute acetic acid. 



Colored Leaves. — The causes of the coloring of leaves 

 in autumn has formed the subject of a series of investiga- 

 tions by Mr. E. Overton. The leaves that turn red he 

 classifies under two heads, those which remain throughout 

 the winter, and .those that fall soon after their change of 

 color. r Microscopic examination show that in both cases 

 the palisade -cells, and the cells that line the air-chambers 



