206 THE AMERICAN MONTHLY [June 



ject. In photographing with all but the lowest powers 

 some form of substage condenser is necessary. This is 

 due to the fact that the light must be focused on the ob- 

 ject to give proper definition. In working with object- 

 ives of from eight millimeters up to but not including 

 oil-immersion objectives, it will be found advantageous 

 to use objectives of lower power as substage condensers, 

 for if so used in ordinary observations they greatly im- 

 prove the definition of objects. In fact, it may be laid 

 down as a general rule that whatever gives the best 

 microscoi^ic definition will give the sharpest photograpic 

 image. Consequently in high-power work it will seldom 

 be necessary to change the microscope attachments when 

 a photograph is to be taken, for in bacteriological work 

 the ordinary Abbe condenser which gives good 

 definitions will, when properly adjusted, give good 

 photographic definitions, statements to the contrary not- 

 withstanding. 



To adjust the light and sabstage condenser proceed as 

 follows: With microscope and lantern in position and 

 substage condenser centred, place the light to be used in- 

 side the lantern body, place an opal or ground glass be- 

 tween lamp and microscope, attach a low power objective, 

 and, seated at the microscope, focus the objective accu- 

 rately on the object. The opal glass is used to reduce 

 the light which otherwise might injure the observer's 

 eye. The ground glass is then removed, a fine wire 

 screen placed close against the front of the lantern con- 

 denser, and by means of the substage condenser au 

 image of the screen is projected on the object. The 

 screen is then removed and a white card held above the 

 eyepiece of the microscope with one hand, while with the 

 other the light is moved about inside the lantern body 

 until the image of the light jirojected on the card appears 

 oval in form and equally brilliant in all parts. If the 

 light is placed too near the condensers, there will be dark 



