2 A MANUAL OF BACTERIOLOGY 



Exercise 1. The Forms of Bacteria 



Using prepared laboratory slides, examine bacteria of different 

 origin. Note that the orgamsms have been stained artificially. 

 You will need to use a microscope having an oil-immersion lens 

 and an Abbe condenser vrith an iris diaphragm (Fig. 1).^ 



Exercise 2. T3rpes of Bacteria 



1. Place a small drop of Gram's iodine solution on a glass 

 slide. With a needle transfer a bit of scum from a hay infusion 

 to the drop of iodine solution. Tease it up and put over it a 

 cover glass. Examine with the microscope. Describe the differ- 

 ent types of bacteria found. 



2. Following the directions given in Exercise 59, stain bacteria 

 from the hay infusion, using methylene blue or carbol-fuchsin. 

 Sketch the types of bacteria seen on the stained preparation. 



3. With a clean knife or needle scrape a little of the material 

 attached to your teeth and spread it in a very thin layer on a 

 cover glass. Dry, fix, and stain as before. Sketch the types of 

 bacteria seen on the stained preparation. 



Exercise 3. Spores 



Search the stained preparations made in Exercise 2 for rods 

 which contain oval glistening bodies. These bodies are spores 

 which, on account of their resistant walls, did not take the 

 simple stains employed. How many spores do you find in 

 a rod ? Examine prepared slides of Clostridia showing rods 

 swollen by the presence of a large spore. Spores are more 

 resistant to unfavorable conditions than the vegetative cell. 



1 A suitable microscope for bacteriological purposes would have both coarse and 

 fine adjustments and the following fittings: 2 oculars, 1 in. (x 8) and 2 in. (x 4) ; 



3 objectives, f in. (16 mm.), 5- in. (4 mm.), and tV in. (2 mm.) oil-immersion objective, 

 mounted on a triple revolving nose piece, together with an Abbe condenser in the 

 substage. It is not so important that the image shall be large as that it shall be sharp 

 and clear. When you have finished for the time being with the oil-immersion lens, 

 remove the oil witli a piece of Japanese lens paper. If the oil has dried upon the lens, 

 soften it by the addition of more oil and allow it to stand several minutes, when it 

 can usually be removed with the paper. If this method does not succeed, you should 

 caU the instructor. 



