220 CLINICAL BACTERIOLOGY AND HjEMATOLOGY 



lower one, and the film will resemble the marks left on a knife which 

 has been pressed on butter and lifted off; such films are useless. 



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 ; it 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. 



I used formerly to recommend the use of forceps for holding 

 the cover-glasses in making these films. The only advantage is 

 that it avoids "steaming" the cover-glasses by the condensation 

 of moisture from the fingers, which may distort the corpuscles. 

 Except when the operator's fingers are very moist it is quite 



Fig. 48. 



unnecessary, and perfect films may be obtained with the cover- 

 glasses held in the fingers. 



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 longitudinally. 

 Paper which is decidedly ridged or ribbed will not answer. 



3. Needle. 



