164 THE AMERICAN MONTHLY [Sept 



A nearer view may often be obtaided, for they will attach 

 themselves to the side of the g-lass to enjoy the lig"ht, 

 which they seem to love. — R. Blig-ht in Pop. Sci. Mo. 



Mucilage Cells, — Methylene blue has the advantage of 

 beinj^ a decisive reag-ent for mucilage in plants ; only some 

 lig-nified cell-walls otherwise take up the color, and the 

 stain may be applied by proper manipulation to dry as 

 well as to fresh plant material. Fresh specimens of 

 leaves, etc., are left for several hours in a solution of 

 methylene blue, 0.4 gm. in 95 per cent alcohol, 100 c. c. ; 

 afterwards cut sections and transfer each to a slide with a 

 few drops of a similar solution, in which four-fifths of the 

 alcohol is replaced by an equal volume of nearly anhy- 

 drous glycerin. The mucilage cells are stained blue in a 

 short time, and after covering the specimens they may be 

 kept indefinitely, the contrast between the stained and 

 unstained portions becoming more marked as time 

 passes. Dried material should first be softened in water, 

 then transferred to strong alcohol prior to cutting sec- 

 tions. — Am. Journ. Phar., Ixx.. 285. 



London Air. — Its dust particles, in a suburb, number 

 20,000 per cubic centimeter in the open air, and 44,000 in a 

 quiet room ; while in the city the totals per cubic centi- 

 meter were 500,000 when taken from a roof, 300,000 in a 

 court, and about 400,000 in a room. In other words, the 

 air of the square mile is 900 per cent thicker than in the sub- 

 urbs; which is in accord with the general experience that 

 fogs are both more dense and more frequent over the center 

 than in the outskirts. But what is especially interesting 

 is to learn that although dust is the great carrier of micro- 

 organisms, there is only one of these articles per 38,000,000 

 atoms of dust. Thus it is calculated that a man could live 

 in the metropolis for seventy years and only absorb 

 25,000,000 microbes into his system from the air, or about 

 the same number as he drinks in a half-pint of unboiled 

 milk. Of course there are other serious objections to 

 dust ; but it is something to know that there is only one 

 microbe to many millions of motes, — London Telegraph. 



