4 4 ME THODS OF EX A MIX A TION. 



a rapid double staining of sputum is desirable. He uses the following 

 mixture : — 



Rosaniline hydrochloride, . . .2 parts. 



Methyl blue, ... 1 part. 



Triturate in a glass mortar. 



Then dissolve aniline oil, . 3 P arts - 



In rectified spirit, . . ■ • l 5 P arts - 



And slowly add distilled water, . .15 P arts - 



Keep in a stoppered bottle ; allow the cover-glass with the hardened 



film of sputum to remain in this solution (warmed) for four or five 



minutes, and then wash in methylated spirit until no more colour 



comes away ; drain thoroughly, and dry. Sections may be stained 



in the same fluid in three or four hours.. Mount in Canada 



balsam. 



Each of the above methods has its own adherents, but the most 

 satisfactory results are obtained by Ehrlich's method, as modified 

 by Koch and Kaatzer. 



Sources of Error in Observation. 



30. In examining stained specimens, the difficulties as regards the 

 identification of the various micro-organisms are to a very great 

 extent removed, but the beginner will, through imperfect staining 

 and inaccurate observation, undoubtedly be led into error, if it be 

 not borne in mind that, unless special methods of treatment be 

 adopted and carried out in all their details, the nuclei or parts of the 

 nuclei retain the germ-tinting reagents. In a great number of cases 

 these nuclei appeared to be greatly broken up, and in such cases it is 

 an extremely easy matter to mistake the fragments of the nucleus for 

 a mass of micrococci in the centre of the cell. 



Compound granular corpuscles, the small rounded masses of 

 fatty granules that are so frequently met with in tissues undergoing 

 fatty degeneration, are also not unfrequently mistaken for masses of 

 micrococci, even in fairly well stained specimens, and albuminoid 

 granules or other amorphous particles are similarly mistaken for 

 stained micrococci. 



Such mistakes, however, cannot be often repeated, and after very 



