io6 
Staining Small Objects . 
in an atmosphere of alcohol), are fixed to the slide by 
means of a thin film of celloidin. The objections to this method 
are, that though it allows of a rapid transference from one fluid to 
another, yet the presence of the film, not only introduces difficulty 
of clearing, but also prohibits the use of ceitain stains which colour 
the celloidin too deeply. 
A considerable step in advance was made by the “Stippling” 
method of Harper and Fairchild (Trans. Wisconsin Acad, of Sc., Vol. 
XII., p 479) in which the fixing fluid together with the objects is 
“ stippled ” in drops by means of a fine pipette, upon the surface of a 
slide prepared with Mayer’s albumen fixative. The fixing fluid partly 
coagulates the albumen and the coagulation is completed by passing 
through increasing strengths of alcohol, so that the objects remain 
firmly fixed to the slide. This method is exceedingly ingenious, but 
is difficult to carry out, is applicable only to very small objects, 
and, as Harper states, a large proportion of the material is lost in 
the process. The method now to he described is applicable to both 
small and large objects (e.g. large Desmids and large teleutospores) 
and when carefully used all the material placed upon the slide is 
held fast. Historically it would appear to be a modification of 
the Harper and Fairchild process, but it was actually arrived at by 
a consideration of the condition of affairs when one melts the 
paraffin of a microtome section which is lying upon a layer of 
albumen fixative. 
The material to be treated is brought up by decantation, 
filtration, etc., if necessary, very gradually, to some clearing fluid 
(xylol, cedar-wood oil, bergamot oil, &c.). Drops of the clearing 
fluid containing the objects are then placed upon tbe surface of a 
slide prepared with egg-albumen ; either in fairly large drops or 
the “ stippling ” process can be used, according to the closeness of 
the objects in the fluid. The drops spread out, but the objects are 
retained by the albumen. When the fixing fluid has evaporated 
and spread out to a very thin layer, the slide is placed slightly 
obliquely, and absolute alcohol is allowed to flow very slowly from a 
pipette over the surface of the slide. The clearing fluid is washed 
away, but the objects are retained in position by the sticky albumen, 
which, being immediately coagulated by the alcohol, holds the 
material fast. The slide can then be treated in the same way as 
one to which microtome sections have been fixed. Of the clearing 
1 Harper states that the method can be made applicable to 
larger objects by washing away the fixative with fairly strong 
alcohol, but in my hands this has led to collapse of the cells. 
