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. — Wakm 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. 



Fia. 51.— Wakm 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 



