154 THE MICROSCOPE. Nov 
of a half-inch strip is drawn its full length through a drop 
of blood on the finger tip not larger than the head of a pin 
the finger tip and the cover glass being previousy cleansed 
thourghly in the usual way. If too much blood be taken 
on the strip the film will be too thick and useless. The 
edge of the strip is quickly drawn across the cover glass, 
the strip being held nearly at rightangles to the surface 
of the glass and before the blood has had time to dry upon 
the paper. In this way is spread on the cover glass (or 
slide if preferred) a fine film of blood which dries very 
quiekly, and in it many excellent fields will be found, with 
the corpuscles lying on the flat and practieally unaltered. 
The cover glass must not be fixed to the slide by any med- 
ium that will rub between the two, causing everything to 
disappear from view. but it must be mounted dry. It can 
be gummed tothe slide by astrip of thin paper, with a 
window exposing the blood smear, when the latter can be 
examined with a dry or an immersion lens. With a good 
quarter-inch objective crescents and the larger pigmented 
parasites, and with an oil twelfth the smaller pigmented 
forms, can easily be seen. The specimens can be thus pre- 
served and examined at any subsequent time, and even 
stained later. The film ona slide can be examined witha 
dry lens without the intervention of a cover glass; then 
stained, dried, and examined without a cover glass with or 
without balsam. If an oil-immersion lens is used, the film 
when dried and unstained should be on the cover glass, as 
the layer of air between the cover glass and the slide, if 
the film is on the latter, prevents the oil working at its 
best. The films should be carefully protected from dust 
before they are mounted. ‘The color of the protoplasm of 
the parasite is not quite the same dried as undried, and of 
course no movement of parasite or of pigment is possible 
in the dried state. Even the unpigmented parasites have 
been detected in the dried form as rings or signets, and 
they have been stained. Blood films treated in the manner 
outlined are subject to less interference than when fixed 
by heat, alcohol, ether, or other means, or when treated 
with one or more staining solutions, washed, dried, etc. 
