162 BACTERIOLOGICAL DIAGNOSIS. 
holding with the other pair of forceps; draw the two 
apart with a steady even pull; they should separate 
easily, and, if all the stages of the process have been 
properly carried out, leave you with two perfectly 
spread films. 
Here again you find whether you have taken the 
right amount of blood. If you have taken too little 
the cover-glasses will be very difficult to separate ; 
may indeed be impossible to do so without breaking 
them. Ifyou have taken too much they will separate 
with great readiness and the blood will spread in 
uneven smears instead of forming a uniform film. 
A word is necessary concerning the method in which 
the cover-glasses are to be pulled apart. They must 
always be kept in the same plane; if this is not done, 
and if the upper cover-glass is lifted from the lower one, 
the film will resemble the marks left on a knife which 
has been pressed upon butter and then lifted off; such 
films are useless. 
The blood may be taken by means of the platinum 
loop, and this is a good plan, as all danger of smearing 
the cover-glass upon the skin is avoided. If several 
films are to be taken a number of platinum loops should 
be provided, as the blood upon them soon coagulates. 
The exact size of the loop can only be learnt by 
experiment, and when one has been found to deliver 
a drop of the right size it should be kept entirely for 
this work and carefully protected from injury. 
Il. MeTHOD WITH CIGARETTE Papers. 
Requisites.—1. Perfectly clean slides. 
2. Some fairly stiff cigarette papers cut in half 
