9 8 BACTERIOLOGY. 



either place the microscope bodily within an in- 

 cubator, with the eyepiece protruding* through an 

 opening, so that we may observe what is going on 

 without moving the preparation, 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, 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 

 middle, half an inch in diameter, and is fastened to 



FIG. 32. SIMPLE WARM STAGE. 



an ordinary slide with sealing wax. The drop to 

 be examined is placed on a large-sized cover-glass 

 and covered with a smaller one. Olive oil or 

 vaseline is painted round the edge of the smaller 

 cover-glass to prevent evaporation, and the prepara- 

 tion is placed over the hole in the plate (Fig. 32). 



The slide bearing the copper plate is clamped 

 to the stage of the microscope (Fig. 33). The 

 flame of a spirit lamp is applied to the extremity 

 of the rod, and the heat is conducted to the plate 

 and thence transmitted to the specimen. That the 



