ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
149 
solidified ones. The method can of course be varied in many ways ; but 
one of the simplest, and one of those which I have used with satisfactory 
results, is the following. At each end of a glass slide (1J in. by 3 in.) 
a narrow slip of glass is fixed A A. This, as will be seen later on, is 
to act as a support. (The surface of the slide on which these slips are 
fixed will be called the upper one hereafter.) Three small drops of 
sealing-wax are dropped on the upper surface of the heated slide (any 
other thick cement, solid, and emitting no antiseptic vapours, at the 
temperature of the body, may be used instead of sealing-wax.) These 
drops will be used to support a cover-glass C, lj in. in diameter, 
at a certain distance above the slide, and thereupon must form 
the apices of a triangle capable of being inscribed in the circumference 
of such a cover-glass. Before placing the drop of fluid on it, the slide 
must be thoroughly sterilized in the flame of a Bunsen burner, or other- 
wise. (The sealing-wax does not interfere with this process.) Then the 
slide is inverted or placed under a thoroughly sterilized plate. A 
cover-glass 0, 1| in. in diameter, is sterilized also, and the surface 
which is to be next to the slide is carefully protected from the 
access of any germ or dust. On this surface a very small drop D of 
sterilized material may be placed, and this drop touched with a wire 
charged with a few organisms. A number of cover-glasses being j>re- 
pared in this way, they may be examined over a sterilized plate with a 
pretty high power, inoculated surface downwards, and not in contact 
with the supporting slide, which must also be thoroughly sterilized, 
until a drop is found to contain the number of organisms wanted. 
Instead of a drop, a streak E E can be used, according to the nature of 
the organisms investigated. On the upper surface of the sterilized slide 
a drop of sterilized nutrient or other medium is deposited by means of 
a perfectly sterilized pipette. The size of the drop depends on the 
thickness one desires to give to the preparation or the surface one intends 
to cover. The diameter of the inclosed film should, in order to prevent 
contamination, never be more than 3/4 in. when the cover is not 
more than lj in. in diameter. (I often use larger covers and slides, 
but this in most cases has no advantage.) The centro of the side 
of such a drop may now be inoculated (in case the cover has not 
been previously inoculated). Then the cover is placed over the 
drop. It should be well supported by the three drops of sealing-wax, 
and should not at this stage flatten much the drop underneath. A heated 
rod is then applied successively over the three drops of sealing-wax, 
until the inoculated fluid has spread evenly over a certain surface under 
central parts of the cover ; the preparation is then ready for the incuba- 
tors. It has, however, to be kept in mind that, owing to the free access 
of air to the surface of the inoculated fluid, it is necessary to keep 
the preparation in a moist chamber. The extremely small size of these 
inoculated slides allows of a large number being packed in an extremely 
small space. Before incubating the preparation it is necessary to select 
out of the micro-organisms which have been sown into the fluid one or 
several, the position and relation of which are carefully noted. 
For this purpose, divided cover-glasses or slides, or, as I prefer, a 
finder, can be used. I have in this way followed the development of 
bacteria and spores of the pathogenic Pyrenomycetes for days and weeks. 
