2384 



Journal of Applied Microscopy 



water on the slide, and with the needle the water is spread over the surface of 

 the slide, covering a space about one-half inch in diameter. 



The slide is allowed to remain until the film is thoroughly dry. Holding the 

 slide by one end, film side up, pass it through the upper 

 part of the flame of a Bunsen burner, or of an alcohol 

 lamp; each passage should consume about one second of 

 time. This is for the purpose of fixing the bacteria to 

 the slide, but where a flame is not at hand this may be 

 omitted, although under these conditions some of the 

 bacteria may come off in the subsequent washing. 



A small, wide mouthed bottle is filled with the staining 

 solution, and the slide, with the dried film, is placed in 

 the stain (see Fig. 11), and allowed to remain from five 

 to ten minutes. It is then removed and the excess of dye 

 washed off. The washing should be continued until the 

 water is no longer colored by the dye. A clean cover 

 glass is now to be placed over the film. One edge of the cover glass is placed 

 in contact with the slide, and then gently lowered into place. 



The excess of water is removed from the slide and cover glass with filter or 

 blotting paper. The preparation is now ready to be examined under the micro- 

 scope. Use the highest power obtainable, an oil immersion lens if possible. 

 Resume : 



1. Spread the film on slide. 

 Dry in air. 



Fix by passing through the flame. 

 Stain. 



Wash in water. 

 Cover with cover glass. 

 Examine. 



Fig. 11. — Mide mouthed 

 bottle filled with stain, 

 for use in staining bac- 

 teria on glass slide. 



2. 



o 

 O. 



4. 



5. 

 6. 



In examining these the maximum amount of light is needed. 



Fig. 12. — Diagram illustrating cell grouping among the Micrococci. 1, Micrococcus (Staphyl- 

 ococcus); 2, Diplococcus ; 3, Streptococcus; 4, Tetracoccus ; 5, Sarcina. 



Make preparations in this way from colonies which present varied appear- 

 ances on the potato cultures, for illustrations of the various form types. 



On the piece of potato exposed to the air will probably be found colonies of 

 various micrococci, or spherical bacteria. The different forms will vary in size 

 and in the grouping of the cells. When spherical bacteria are isolated or 

 arranged in irregular groups they are spoken of as Mierococci^ sometimes Staphyl- 

 ococci (Fig. 12, 1). When they are in pairs they are called Diplococci (Fig. 12, 2), 



