104 TYPE STUDIES 



C. Label eacli potato culture -with a number and write an 

 account of each, giving (1) day and hour of inoculation, and 

 (2) method. Examine the cultures for several successive 

 days and record the changes from day to day. Describe and 

 sketch the appearance of the growths, their color, form, 

 and consistency. 



101. Fluid cultures of bacteria.* * 



A. Hay infusion. Place some hay in a small quantity of water 

 and leave in a warm place for a few days. The scum that 

 forms is principally bacterial and composed largely of Bacillus 

 subtilis. Later quantities of infusoria, chiefly Faramcecium, 

 will develop. 



B. Mother of vinegar. Examine the brownish mass called mother of vine- 

 gar from a vinegar jar or bottle. This mass Is a good illustration 

 of what is called a zooglcea, — that is, a gelatinous growth developed 

 by bacteria. 



C. Decaying algoe. Allow algae, such as Vaucheria or Spirogyra, to decay 

 in a bottle in a warm place. A bacterial scum will form that generally 

 contains quantities of the spiral filamentous type, Spirochete. Spiro- 

 choBte will also generally develop in filtered bean or pea broth made 

 by boiling crushed beans or peas. Note the putrid odor. 



102. Microscopical studies of bacteria. 



A. Examine underh.p. the scum from a hay infusion (Sec. 101, A) 

 for the hay bacillus, Bacillus subtilis. Note : 



1. Colorless rod-shaped cells, solitary or forming filaments 

 of various lengths, their movement in the water, and their 

 size as compared with such infusoria as may be present, 

 particularly JParamoeciwrn. Draw. 



2. Study under very high magnification, if desired, the crosswise 

 division, or fission, of the rods. This study will demand an immer- 

 sion lens. 



3. Place some of the scum in distilled water and after several days, 

 when the food supply has become exhausted, study under an immer- 

 sion lens the small, thick-walled spores formed within the rods. 



4. Other bacteria will probably be present besides the hay bacillus. 

 Search for spherical types, Micrococcus, and filamentous forms, the 

 latter sometimes spirally twisted and motile, Spirillum or Spirochade. 



