CH.i.] MICROSCOPIC EXAMINATION. 5 



ascertain as far as possible the appearances, chemical 

 reactions, and general morphology of perfectly fresh speci- 

 mens. Blood, juices, tissues, and fluids in which the micro- 

 organisms have been growing, are subjected directly, without 

 any previous preparation, to microscopic examination. With 

 artificial nourishing media in which micro-organisms have 

 been growing, the examination of fresh specimens is of 

 great importance, for the reason that the organisms can be 

 easily identified and their size and general morphological 

 characters be more correctly ascertained than after drying, 

 hardening, and staining. Besides, the chemical reactions 

 can be satisfactorily studied in fresh specimens only. All 

 one has to do is to draw up with a capillary pipette or to take 

 up with the point of a needle a drop or particle of the 

 material, to place it on an object-glass, and to cover it up 

 with a thin cover-glass. Where one has to deal with liquids, 

 such as artificial nourishing fluids, blood serum, tissue- 

 juices, secretions, transudations and exudations, no addition 

 is required. In the case of more solid material, such as 

 solid artificial nourishing material, bits of tissue, &c., the 

 addition of a drop of neutral previously well-boiled saline 

 solution (of 0*6 to 075 per cent.) is advantageous .although 

 not absolutely necessary, since by pressing down the cover- 

 glass a layer of the material sufficiently thin for examination 

 can be obtained. In some instances a bit of tissue .can be 

 teased out into fine particles by means .of two clean needles. 

 Where it. is a question of micro-organisms sufficiently con- 

 spicuous by their shape, size, and general appearance, their 

 identification in the fresh condition is not difficult ; this is 

 the case with bacilli, actinomyces, and mycelia, but in the 

 case of micrococci, especially when isolated ox in couples, 

 and lying in blood, juices, or tissues, their recognition is 

 often extremely difficult. When in laige clumps, such as 



