THE BACTERIOLOGICAL LABORATORY 



21 



substage condenser (Fig. 3fi). This condenser, first 

 described by Professor Abbe (of the University of 

 Jena), 1 is of very short focus, and collects the light 

 reflected by the flat mirror into a cone of rays of 

 very large aperture, and projects it on the object. 

 Abbe's condenser is focussed on the object by coarse 

 and fine adjustments. ' When the whole field is to 

 be examined, the lamp is used with the whole 

 breadth of the flame, but when a small portion is to be 



K 



FlG. 4. MlCROPHOTOGRAPHIC APPARATUS. 



(After Carl Zeiss.) 



specially examined with a high power, it is necessary 

 to turn the lamp so that the edge of the flame is pre- 

 sented, by which the light is very much intensified. 

 The correct distance at which to place the lamp can 

 only be found out by practice. A piece of blue glass 

 should be interposed between the lamp and the con- 

 denser : this can be done by having it fitted into the 

 condenser or by having a separate stand ; different 

 shades of blue will be found useful for various objects. 



1 Archivfur Mikr. Anat. vol. ix. p. 496. 



