1. Thin smears are better suited for the examination of 

 parasites and blood cells and hence make differential diag- 

 nosis easier. 



If the blood specimen contains but few parasites it re- 

 quires a long search to find them in a thin smear. Before the 

 thick drop method came into vogue the accepted rule was 

 that the film must be examined for a full hour before it 

 could be pronounced negative. This was often necessary, 

 because many patients had taken a dose of quinine on their 

 own initiative before consulting the doctor, with the result 

 that it took a very long time to discover the few remaining 

 parasites. 



Parasites are very scarce during the initial stages of the 

 fever (Korteweg), and the same is true in the case of 

 "healthy" carriers. 



2. With a thick drop the same amount of blood may be 

 examined in five minutes which requires a full hour with a 

 thin smear. Hence the thick drop method is the only feasible 

 one for large scale investigations, such as the examination 

 of a great number of inhabitants of the same village, healthy 

 parasite carriers or persons who have already had a dose of 

 quinine. 



The thick drop method increases the number of positive 

 finds, but it requires a more accurate technique for staining 

 than the thin smear method. If the following rules are ob- 

 served, however, thick drop films will in many cases enable 

 the investigator to use them also for the differential diag- 

 nosis of the various forms of malaria. 



Hence our advice is as follows: For routine examination 

 the thick drop is preferable to the thin smear; but the latter 

 is needed when more delicate cytological examinations have 

 to be made. 



STAINING 



The same stain may be used for both the thin smear and the 

 thick drop. Giemsa stain may be obtained ready made in 

 small bottles from many dealers or it can be prepared from 

 the following recipe. 



