4: . Dairy Bacteriology. 



spore forms that resist the action of heat in pasteurizing 

 milk. 



Movement. Many bacteria are unable to move from 

 place to place. They have, however, a vibrating movement 

 known as the Brownian motion that is purely physical. 

 Many other kinds are endowed with powers of locomotion. 

 Motion is produced by means of tine thread-like processes 

 of protoplasm known as cilia (sing, cilium) that are de- 

 veloped on the outer surface of the cell. By means of the 

 rapid vibration of these organs, the cell is propelled through 

 the medium. Nearly all cocci are im motile, while the 

 bacilli may or may not be. These cilia are so delicate that 

 it requires special treatment to demonstrate their presence. 



Classification. In classifying or arranging the different 

 members of any group of living objects, certain similarities 

 and dissimilarities must be considered. These are usually 

 those that pertain to the structure and form, as such 

 are regarded as most constant. With the bacteria 

 these differences are so slight that they alone do not suffice 

 to distinguish distinctly one species from another. As far 

 as these characters can be used, they are taken, but in 

 addition, many characteristics of a physiological nature are 

 added. The wa} T that the organism grows in different kinds 

 of cultures, the by-products produced in different media, 

 and effect on the animal body when injected into the same 

 are also used as data in distinguishing one species from 

 another. 



Conditions favoring bacterial growth. The bacteria, in 

 common with all other living organisms are affected by 

 external conditions, either favorably or unfavorably. Cer- 

 tain conditions must prevail before development can occur. 

 Thus, the organism must be supplied with an adequate 



