MORPHOLOGY OF LEUCOCYTES AND RED CORPUSCLES 225 



which Jenner has been used, the main point being that the nucleus 

 of the leucocytes is a fine purplish-red ; the leucocytes, however, 

 can be easily recognized from the coloured plates. 



Leishman's method is the best for working with malaria and all 

 parasitic protozoa, the nuclei of which are stained a bright red. 

 For ordinary blood-work I personally prefer Jenner (perhaps 

 because I am more used to it), and the practitioner is recommended 

 to choose one process and stick to it. If he is likely to need it for 

 malaria or other parasites, Leishman's stain should be used. 

 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 : 4 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 difficult part of the pro- 

 cess, 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 distinguished with great ease with the |-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 resemble those afforded by 

 Jenner's stain, except that the fine eosinophile granulations in the 

 polymorphonuclear cells are always less obvious and often quite 

 invisible. It is also suitable for malarial parasites and bacteria. 



The practitioner is recommended to practise this method of 

 staining, as it does not require any reagents which are not to be 

 found in every well-stocked surgery. The watery solution of 

 methylene blue which is used as a counterstain for the tubercle 

 bacillus and some red ink are all that are necessary. 



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