GENERAL BIOLOGY 



B. STUDY OF DIFFERENT STAGES, TYPES 

 AND CULTURES OF BACTERIA 



I. ACTIVE STAGES. 



Study bacteria from various media, viz. : Pasteur's Solution, 

 Beef Tea, Infusions of Hay and Peas, Potato and Gelatin Cultures, 

 Sewage, etc., and observe and draw the following forms: 



1. Cocci; rounded forms occurring singly or in bead-like rows ; 

 without flagella. 



2. Bacilli; rod-like or thread-like forms. 



3. Spirilla; spiral forms which may consist of many turns 

 (Spirillum Spirochaeta) or of only a fraction of one turn (Vibrio 

 "Comma bacillus"). 



In these various forms observe the following points : 



First ; size, measure. 



Second ; structure. Can you notice any change of shape in an in- 

 dividual? Any difference between the external and internal por- 

 tions? Any peculiarity of the ends in the longer forms? 



Third; movements. Some vital, others purely physical (Brown- 

 ian movements). The former progressive, the latter vibratory 

 and irregular. Study the Brownian movements in particles of 

 Chinese ink in water. Put a few drops of fluid containing bacteria 

 on a slide, hold the slide over a Bunsen flame and kill the bacteria 

 by boiling, cover and examine with high power. Can you notice any 

 movement of the dead bacteria? Compare with movements of 

 living ones. 



II. RESTING STAGES. 



Examine the scum ("Zooghca") from the surface of various 

 liquids, especially the hay infusion ; it consists of myriads of bac- 

 teria in a resting condition imbedded in a gelatinous substance, 

 the "bacterial jelly." 



III. STAINING AND MOUNTING. 



Spread a small drop of liquid containing active bacteria on a 

 clean cover glass and let it dry slowly ; then pass the glass through 

 a Bunsen flame two or three times to coagulate and fix the bacteria 

 upon the glass. Put a drop of Methylen Blue or Gentian Violet 

 upon the glass. After five minutes rinse with distilled water and 

 mount in a drop of water upon the slide. If a permanent mount is 



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