MICRO-ORGANISMS AND FERMENTATION. 



CHAPTER I. 



MICROSCOPICAL AND PHYSIOLOGICAL EXAMINATION. 



1. Microscopical Preparations, Staining, and 

 Microchemical Examination. 



THE Microscope will always be the chief means for investigating 

 micro-organisms, for these are, 

 as individuals, almost always 

 invisible to the naked eye. 



The microscope is made up of a 

 mechanical and an optical part. The 

 mechanical part, or stand, consists of 

 the foot, the Stage, the tube carry- 

 ing the lenses, and the adjustment for 

 regulating the distance between the lens 

 and the object lying on the stage. The 

 adjustment is partly " coarse " (a screw 

 engaging in a toothed gear attached to 

 the tube) whereby the tube can be 

 rapidly raised or lowered, partly " fine " 

 (a finely cut screw) by means of which 

 the tube can be gradually raised or 

 lowered, after finding the object with 

 the coarse adjustment. The tube 

 commonly consists of two telescoping 

 parts. A table, which usually accom- 

 panies the instrument and gives the 

 scale of magnification, records the cor- 

 responding length Of tube either in 



Fig. 1. 



millimetres (usually 180 mm.) or in inches (usually 10"). 



The optical part consists of the lenses and illuminating apparatus 



(a mirror and Abbe condenser). 



1 



