90 PHARMACEUTICAL BACTERIOLOGY. 



(concave center) are required. Touch a small drop of the culture to be 

 examined on the center of a clean and heat-sterilized cover-glass, by means 

 of a heat-sterilized platinum wire loop. Smear a little plain petrolatum 

 around the rim of the concavity of the slide and invert the cover-glass prep- 

 aration upon the slide, pressing it gently in place on the petrolatum. 



10 ^-r *7T, 



FIG. 43.- 



-Jeffer's circular counting plate forPetri dish cultures. The entire area (100 sq. 

 cm.) is marked off into ten equal sectors of ten sq. cm. each. 



Examine for a period of several hours or longer as may be desired. Cell 

 division, spore formation, etc., can be studied very conveniently. Observa- 

 tions on the effects of temperature and rate of septation may be made. The 

 hanging-block preparation is made by touching the surface of a cube of 

 nutrient agar with the bacteria and then applying this bacterial side against 



