CHAPTER XXXV 



METHOD OF PREPARING AND EXAMINING THICK- 

 FILMS FOR THE DIAGNOSIS OF MALARIA 



By 



M. A. Barber and W. H. W. Komp 

 U. S. Public Health Service 



Slides should be well cleaned. It is a good plan to wipe shdes 

 cleaned in the ordinary manner with an alcohol-wet cloth to free 

 them from grease. Old slides are usable if not fogged or scratched 

 If any dust gets on the slides in carrying them to the field, brush 

 each one on a clean cloth just before using. 



Select slides of a proper length to fit the slide box, and suffi- 

 ciently thick to fit the mechanical stage of the microscope. 



Collecting blood specimens. It is essential that the blood be free 

 from dirt coming from the skin, from dust or other debris. 

 Clean the skin with alcohol and gauze. Dry, Prick the skin deeply 

 enough to allow the blood to well up in a large drop. Touch 

 the slide to the upper part of the drop, avoiding as far as possible 

 the blood which has been in immediate contact with the skin. 

 In any case, avoid rubbing the skin with the flat of the slide or 

 scraping it with the edge. Bacteria or other debris, which confuse 

 the search for parasites in the thick-film, usually come from the 

 dirt which is carried by the blood from the surface of the skin ; 

 and cleaning with alcohol and gauze does not always wholly free 

 the skin from such debris. 



It is possible to get fair specimens from a dry skin without 

 any preliminary cleaning if one takes the blood from the top of the 

 drop only, but it is better to clean the skin as an additional 

 precaution. We usually take the blood from the upper surface 

 of the middle finger, pricking the skin about one-half centimeter 

 below the base of the nail. 



One can spread the blood sufficiently by dragging the drop on 



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