l68 BACTERIOLOGICAL DIAGNOSIS. 



Jenner's stain is suitable for a study of the parasite of 

 malaria, which it stains blue. It may be used for the 

 detection of bacteria. 



3. Eosin and methylene blue used separately. 



In this method the films are to be stained with the 

 eosin first and then with the methylene blue. Its 

 successful application requires a certain amount of 

 practice. 



The eosin used must be in watery solution, and the 

 exact strength does not matter ; four per cent, is a 

 convenient strength to use. Most specimens of red ink 

 (slightly diluted) will do quite well. The films are 

 to be stained in this solution for three or four minutes ; 

 no harm will result if they are left in much longer. 

 They are then washed and immersed in a saturated 

 watery solution of methylene blue. This is the diffi- 

 cult part of the process, for no general rule can be 

 given as to the length of time for which this stain must 

 be applied ; it may be ten seconds, or it may be two or 

 three minutes. The only safe way is to stain the film 

 for a quarter of a minute, wash it, and then examine it 

 under the low power of the microscope. If the film is 

 properly stained the nuclei of the leucocytes will be seen 

 as blue points which can be distinguish with great ease 

 with the f inch objective. If they are not visible the 

 methylene blue must be applied for about a quarter of 

 a minute more and the examination repeated. When 

 the nuclei are seen to be well stained the film is dried 

 and mounted. 



This process gives results which resembles those 

 afforded by Jenner's stain except that the fine eosino- 

 phile granulations in the polymorphonuclear cells are 

 always less obvious and often quite invisible. It is 

 also suitable for malarial parasites and bacteria. 



