4. Vibrio; like Bacillus but with bent joints. 



5. Spirillum; elongated threads rolled up into a more or less 

 perfect spiral. 



6. Spirocliacta ; like Spirillum but longer and more closely rolled, 

 and without flagella. In these various forms observe the following 

 points : 



First, size, measure. 



Second, structure. Can you notice any change of form 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 (Brow man 

 movements}. The former progressive, the latter vibratory around 

 a stationary center. 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 move- 

 ments of living ones. 



G. RESTING STAGES. 



Examine the scum ("Zoogloea") 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. 



H. CHEMICAL TESTS. 



Spread a small drop of liquid containing motile 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 a slide. If a permanent mount is; 

 desired thoroughly dry the glass after rinsing and mount in Canada 

 Balsam. 



Treat some of the Zoogloea in the same way and observe that the 

 bacteria stain more deeply than the substance in which they are 

 imbedded. 



I. STUDY PREPARED SLIDES OF PATHOGENIC BAC- 

 TERIA. 



J. DEMONSTRATION OF BACTERIA SEEN WITH "DARK 

 FIELD ILLUMINATION". 



28 



