128 THE NORTHERN MICROSCOPIST. 
The series of drawings to which we refer are magnified 400 
diameters, but it is stated in the text that powers of 800 and 1,000 
diameters were employed where necessary. An inspection of the 
series which illustrate Dr. Cunningham’s researches show us clearly 
that other than fungi spores are present in the air. Lichen spores 
and algz spores are normal constituents of the air, and if we allow 
these why should we be so unwilling to admit the presence of Bacillus 
and Bacteria spores which are so much more exceedingly minute. 
Whether these organisms are really the causes of the various 
diseases is quite another question, and in this connection an 
abstract of some work which has been done in this direction may 
be given on some future occasion. 
DOUBLE 'STAININE 
By ARTHUR J. DOHERTY. 
HERE are few microscopic objects which are more beautiful 
and interesting, and more worthy of a place in the cabinet 
than stained vegetable sections; and it is a matter of surprise, 
considering their great popularity, that the number of persons by 
whom they are prepared is, comparatively speaking, small. It 
appears, however, that this inequality is attributable, not to any 
difficulty in the art itself, but to the paucity of instruction ; for it 
cannot be doubted that less has been written upon this subject 
than upon any other branch of microscopical study. Certainly 
Double Staining does not stand isolated from all other departments 
of the science by an entire absence of information regarding it, but 
the subject has nevertheless been treated upon only in such jour- 
nals as one would not directly think of consulting with reference to 
it, whereas those works which ought manifestly to have exhausted 
the subject have dismissed it with a few words, or a chapter upon 
the staining of animal tissues only. 
Perhaps the best paper which has yet been published on double 
staining is that which appeared in “Science Gossip” for January, 
1880; but even the process therein described is in several points 
open to modification and improvement. It is in the hope, there- 
fore, of supplying a want which must have been long felt that this 
article has been written; and though it would be perhaps pre- 
sumptuous to say that the method here advocated is in anyway 
superior, or even equal, to many others which may be adopted, we 
believe it can be affirmed that it is the simplest and cheapest yet 
made public. 
The art of staining in carmine and green consists of five stages 
or processes,—(1) decolourising the sections, (2) washing the same, 
