7O LABORATORY BACTERIOLOGY 
EXERCISE XXI 
A STUDY OF CERTAIN PYOGENIC BACTERIA 
104. There are a number of bacteria which are able to cause 
suppuration, but ordinarily the formation of pus is due to the 
presence of certain streptococci and micrococci. A number 
of bacilli, especially B. co and Ps. pyocyaneus, are frequently 
found as the apparent cause of suppuration. As it is impossible 
to study more than a few of these species, two of the most 
common and one of the more rarely encountered organisms 
in suppurating wounds and abscesses are chosen for special 
study. 
105. Work for this exercise. Inoculate a tube of each 
medium in groups A and B from each of the cultures of 
Streptococcus pyogenes and Micrococcus (Staphylococcus) pyo- 
genes and Ps. pyocyaneus which will be furnished. 
Describe the cultures of 2s. fluorescens liquefaciens and 
examine the bouillon culture microscopically in a hanging-drop 
and in a stained preparation. 
Examine and describe the milk, bouillon, agar, and gelatin 
cultures made from the colonies from milk and water plates. 
Read carefully the chapter on pyogenic bacteria in the 
text-books. 
Give in the notes a definition of each of the following terms : 
saprophytic, parasitic, pathogenic, and pyogenic bacteria. See 
text-books. \ 
