BACTERIA 



LXXII. STUDY OF BACTERIA. 



Apparatus. Hay, milk, meat, test tubes with corks to fit, slides, 

 cover glasses, compound microscope, sterilized absorbent cotton, 

 methyl green, corrosive sublimate. 



Directions- A. Prepare three test tubes as follows: 

 Put in one some pieces of chopped hay and cover with water; 

 in the second some milk; in the third some meat, covered 

 with water. Let these stand uncovered, in a warm place, 

 for several days. Describe the changes that take place in 

 the appearance and odor of the contents. Note the scum 

 that appears on the surface. Mount some of this scum on 

 a slide and cover with a cover glass. Examine with the 

 high power of the microscope. Note the masses of moving 

 forms (bacteria) that make up this scum. Sketch the shape 

 of some of these bodies. (If a drop of methyl green be run 

 under the cover glass, the structure will be clearer.) 



B. Prepare four tubes as follows: Fill each tube with 

 milk. Pack one in ice; leave the top open and label it 

 No. 1. Boil the contents of the second, stopper with a cork 

 that has been boiled in water, and leave in a warm place ; 

 label this No. 2. Boil the contents of the third one and 

 stopper with sterilized absorbent cotton; label this No. 3. 

 Place No. 3 with No. 2. Place the fourth, labelled No. 4, in 

 a warm place, uncorked. After several days examine the 



111 



