l62 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. If you 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. 



II. METHOD WITH CIGARETTE PAPERS. 



Requisites. i. Perfectly clean slides. 



2. Some fairly stiff cigarette papers cut in half 



