Laboratory Outline for General Bacteriology 



measurements of the smallest and largest are required in addition 

 to the size of the majority. Measure at least ten of the medium 

 sized ones and average them in finding the size of the majority. 

 If bacteria are spherical only one dimension diameter is re- 

 quired ; if rod shaped two dimensions length and width are re- 

 quired. Measure length and width of the same organisms. 



To be one micron in length the bacterium has to extend 

 from one line to the corresponding point on the next line, that is, 

 across one space and one line. The lines have width and on most 

 of the scales the width of the line is about .3 micron and the width 

 of the space .7 micron. Now if a bacterium is just covered by 

 a line we know the measurement is .3. If it projects beyond the 

 line it is possible to make an accurate estimate of the proportion 

 of the .7 covered which added to the .3 gives the size; or if it just 

 fills the space between two lines it is .7 micron. The scale may 

 be moved in any direction by turning the eyepiece around. 



Multiply apparent measurements by the microscope constant 

 and record results in the following form : 



For Rods 



Smallest Largest Average 



Length x width Length x width Length x width 



Arrangement 



Smallest 

 Diameter 



Arrangement 



When through with the microscope carefully wipe cedar oil 

 from lens with lens paper furnished. Also remove oil from slides. 



Laboratory note books about 6% X S 1 ^ inches are preferred. 

 These are to be left on the table at your place. They are not 

 to be taken from the laboratory. 



STERILIZATION 



Sterilization is the destruction of all forms of life. It may 

 be accomplished in various ways. Only the common methods of 

 sterilization by heat will be considered here. 



Sterilization in a naked flame. The simplest means of sterilizing 

 a metal instrument is to heat it in the flame. This method is usually 



13 



