6 CLINICAL BACTERIOLOGY AND 



cerned. The instrument is also fitted with an arched limb, 

 which gives a large working space above the object stage, 

 and incidentally acts as a convenient handle for lifting the 

 microscope without putting any extra strain upon some of 

 the other vital parts. 



The stage is circular, and can be rotated on its own 

 axis; it is also fitted with a centring arrangement, which 

 is an advantage when making an examination of urinary 

 deposits, etc. 



The mechanical stage is detachable, and is so fitted to 

 the limb of the microscope that after removal it can be 

 screwed back and occupy exactly the same position each 

 time. 



The instrument, of course, inclines to a horizontal posi- 

 tion, and possesses all the necessary movements for ordi- 

 nary bacteriological purposes. 



The Use of the Microscope. 



Beginners should accustom themselves to use either eye, 

 and the unemployed eye should remain open and passive. 



Daylight is the best illuminant, and especially so if 

 reflected from a white cloud. Direct sunlight, of course, is 

 useless. As the majority of practitioners, however, of 

 necessity do their microscopical work when the light of 

 day has departed, artificial illumination is called into requi- 

 sition. There are some excellent illuminants made by 

 microscope-makers for this purpose, but an ordinary gas or 

 oil light suffices for one's needs. 



When examining an object with the dry lens, the concave 

 mirror should be used, which converges the light on to the 

 object. With an oil immersion lens a flat mirror should be 

 used ; the rays reflected are converged b} T the condenser 

 and brought to a focus on the object, so that by the use of 

 the condenser a considerable amount of light is obtained. 

 To reflect the light on to the condenser, the mirror should 

 be moved about until a suitable angle is arrived at. 



To a beginner this is often somewhat difficult, in which 



