CHAPTER VIII 



MICROSCOPIC METHODS 



The fact that bacteria, yeasts, and molds are so minute 

 necessitates the constant use of the microscope in the in- 

 vestigation of the size, shape, and arrangement of cells of 

 bacteria, the form of yeast cells, and the method of spore 

 production and general morphology of the molds. For 



Fig. 49. — Diagbammatic repeesentation of the optics of the oil 

 immersion lens. 



many purposes the lower powers of the compound micro- 

 scope may be used, but in a critical study of the individual 

 bacterial cells it is customary to employ the highest power, 

 or the homogeneous oil immersion objective. 



The Oil Immersion Objective.— Even a superficial exam- 

 ination of the various objectives used on compound micro- 



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