little practice will enable one to make films with 

 the upper and lowfer edges more or less parallel ' 

 with the edges of the slide, and terminating in a 

 pointed manner about half an inch from the right 

 hand end of the slide. Practically the whole of 

 the dropiof blood is then upon the shde, and the 

 edges to which the leucocytes tend to find their 

 way are in a suitable position for examination 

 (see differential counting of leucocytes, p. 41). 



13. In the case of very anaemic bloods, e.g., 

 those of ' malarial cachexia,' difficulty will arise 

 from the film being too thin. The needle in this 

 case must be carried very loosely and rapidly along 

 the slide and a thicker film thus made. When 

 blood with difficulty adheres to the slide, good 

 evidence of extreme anaemia is obtained. 



The Preparation of Wet Films 



A wet film is not so easy to make as a dry 

 film, and requires cleanliness and rapidity of 

 manipulation. Wet films are therefore difficult to 

 make in dusty countries, where a single particle of 

 grit will mar the process. 



Before proceeding to make films, several glass 

 slides and coverglasses should be carefully cleaned 

 and polished with a dry pocket handkerchief, and 

 wrapped in clean smooth paper, to ensure the 

 absence of dust or grit. In making a wet film the 

 result may be marred by — 



1. Too small or too large a drop of blood. 



2. Too slow manipulation allowing the drop 

 of blood to partially clot. 



3. An uneven coverglass or a coverglass with 

 a minute bubble or speck in its substance. 



4. Dust of any kind. 



