72 



GENERAL MICROBIOLOGY 



of the division line as determined in the above table. This 

 gives the measurement directly in microns. 



Microorganisms may be measured more accurately by 

 mounting them in Chinese ink, as they cannot move, are 

 not shrunken or distorted as often occurs with stained speci- 

 mens, and are clearly seen. Preparations stained with 



FIG. 26. Ocular Filar Micrometer for Very Exact Measurements. 

 By means of a micrometer screw a line is moved across the 

 field. The distance is measured by means of the divisions on 

 the drum. 



aqueous-alcoholic dyes stand next in preference, never 

 strong stains like carbol-fuchsin, anilin-water dyes, or 

 saturated alcoholic solutions of dyes. 



II. Using a Filar Ocular Micrometer. The filar ocular 

 micrometer is an instrument for the accurate measure- 

 ment of microscopic objects. It consists of an ocular, 

 between the eye and field lenses of which there is a scale 

 ruled on glass in millimeters and half millimeters, below 



