NUTRIENT MEDIA AND METHODS OF CULTIVATION. 



123 



Warm Stages. To apply warmth while a preparation is under 

 continuous observation, we must either place the microscope bodily 



FIG. 50. WARM STAGE. 



within a special incubator, with the eye-piece protruding through an 

 opening, or we must employ some means of applying heat directly 

 to the preparation. 



A simple warm stage may be made of an oblong copper plate, 



FIG. 51. WARM STAGE SHOWN IN OPERATION. 



two inches long by one inch wide, from one side of which a rod of 

 the same material projects. The plate has a round aperture in the 



