CLASSIFICATION OF BACTERIA 23 



Ex. 14. Observe the germination of spores on an agar 

 "hanging block." 



Take 10 c.c. of melted agar medium and pour it into a sterile 

 Petri dish about 4 inches in diameter. After cooling cut out of 

 it some square pieces of the solidified agar about 8 to 10 mm. 

 across with a sterile knife. Lift up a piece or block and place 

 it on a sterile glass slide ; cover it with a bell jar to keep off dust 

 until wanted. 



Take a small amount of a culture containing spores from agar 

 or other medium and mix it with i c.c. of sterile broth in a sterile 

 test tube heat the mixture for ten minutes in a water bath at 

 75 C. to kill all growing organisms ; the spores remain uninjured. 

 Spread a small loopful on the surface of the agar block and 

 cover with a thin sterile cover-slip. Now run a needle under 

 the lower surface of the agar and lift the cover-slip with the 

 block attached to it; place it over a culture cell (made by 

 cementing a rubber, metal, or cardboard ring to an ordinary 

 slide with Canada balsam or other cement) so that the agar 

 block hangs down into the cell. 



Before putting on the cover-slip a small amount of vaseline 

 may be smeared round the edge of the cell to prevent evapora- 

 tion of the agar medium. 



Place the whole now in a large Petri dish in an incubator 

 at 25 to 30". Make observations of the germination of the 

 spores and subsequent growth of the bacteria through the cover- 

 slip at intervals of three to six hours. 



Ex. 15. Try and observe the germination of the spores of 

 bacteria introduced into sterile broth as above, a drop of the 

 mixture being arranged as a hanging drop as figured and 

 described in Ex. 35. 



5. Classification of Bacteria. The bacteria form a class 

 of the sub-kingdom Schizophyta or Fission-plants, thus: 



Sub- Kingdom. Schizophyta. 

 Class I. Schizophycece or Blue-green Algae. 

 Class II. Schizomycetes or Bacteria. 



