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THE FUNGI 365 
culture media employed are both solid and liquid. Beef broth 
or nutrient bouillon forms the basis of most of the culture media. 
To this either agar agar or gelatin are added to solidify the 
medium (solid media) and various chemical substances and 
sugars for the purpose of studying the physiological character- 
istics of the various forms. Formulas for the preparation of 
various culture media and directions for the isolation of bacteria 
will be found in the National Formulary VI and in works of 
bacteriology and mycology. 
Forms oF BAcTERIA.—Bacteria occur as spheres, straight 
rods or cork-screw like (bent rods) forms (lower bacteria) or as 
filaments (higher bacteria). The spherical shaped form is 
Fic. 268. Fic. 269. 
Fic. 268.—Monotrichous bacteria. Microspira comma. (After Migula from 
Schmidt and Weiss and Marshall.) 
Fic. 269.—Lophotrichous bacteria. Pseudomonas syncyanea. (After Migula 
from Marshall.) 
termed a micrococcus or coccus (plural-micrococct or cocci). The 
straight rod form is called a baczllus (plural-bacill:). The cork- 
screw shaped form is known as a spirillum (plural-spirila). 
Mortury.—A large number of bacteria possess the power of 
independent movement when observed in a fluid medium which 
will permit of their locomotion. This true movement should be 
distinguished from the so-called “Brownian movement,” a quivering 
or oscillating phenomenon shown by minute particles or bodies 
when freely suspended in a suitable fluid. True movement is: 
due to the activity of the living cell, whereas Brownian movement 
is a purely physical phenomenon due to the bombardment of 
particles, dead bacteria or non-motile bacteria, by the molecules 
of the menstruum. In true movement the individual form moves 
from one part of the microscopic field to another, whereas in 
