200 THE AMERICAN MONTHLY [June 



incident to changing the slide from one stand to another 

 and refindiug a given field is avoided. Every worker, 

 especially in bacteriology, knows the difficulty and time 

 spent in refinding a field once lost. The microscope 

 stand may be of any well-constructed form. Any stand 

 which can he depended upon for clinical or laboratory 

 work can he used for photomicrography. For all-around 

 photographic work it should have a suhstage ring and 

 adapter for using objectives as substage condensers. A 

 mechanical stage is convenient but not necessary. The 

 microscope is used in the upright position. This position 

 rather than the horizontal is to be preferred for several 

 reasons. The upright position is necessary when mova- 

 ble objects, as colonies of bacteria floating on liquefied 

 gelatin (Eig. 4), are to be photographed, or when, as in 

 clinical photomicrography, photographs have to be made 

 of urinary deposits. In bacteriological work, when 

 bacteria are stained on the cover glass and examined or 

 photographed before the balsam is dry, the cover is 

 apt to slip if the microscope is used horizontally; but 

 this does not occur with the microscope used vertically. 



The horizontal position and long extension of camera 

 is necessary for some classes of work, particularly when 

 large pictures have to be taken and when it is desired to 

 obtain high amplification by extension of camera rather 

 than by high eyepiecing, or when test diatoms have to be 

 photographed with very high amplifications. For prac- 

 tical work, however, up to amplifications of one thousand 

 diameters, and for photographs for illustration or repro- 

 duction, which are seldom required of over three and one- 

 half or four inches in diameter, the upright position of 

 microscope and camera is much to be preferred, on ac- 

 count of its ease of application and practical advantages. 



The vertical position of the microscope necessitates a 

 similar position for the camera. To allow easy working 

 distance the camera is hung on a rackwork attached to a 



