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PRINCIPLES OF BACTERIOLOGY 
(b) Staphylococcus pyogenes albus (white) produces 
white pigment. 
The aureus is the most frequent. The albus causes 
the stitch abscesses seen after operations. 
VIII. Bacteriologic Diagnosis 
Bacteriologic diagnosis is easy and rests on the fol¬ 
lowing : 
(a) Gram-positive cocci arranged in clusters. 
(b) Grow readily on simple (meat extract) media. 
(c) Liquefy gelatin, coagulate milk, produce acids, 
form no gas on sugar media. 
IX. Immunity Treatment 
None for acute infections. For chronic infections 
such as continuous abscess formation, persistent pus dis¬ 
charge, etc., a staphylococcus vaccine gives good results. 
Vaccines are prepared as follows: 
A 24-hour-old agar culture of staphylococcus is ob¬ 
tained; about 10 c.c. of sterile salt solution are poured 
into the culture tube; the growth is gently scraped off 
with a platinum loop (care being taken not to scrape 
any particles of agar). The bacterial emulsion is poured 
into a killing tube (this is an ordinary test tube but with 
a long drawn out neck) in which 8 to 10 glass beads are 
placed, the tube is scaled off and shaken for an hour by 
hand (or for ten minutes in a special “vaccine shaker”); 
the narrow tip is broken off and a few drops are poured 
into a sterile watch-glass, the tube is scaled again and 
placed in a water-bath at 58° C. for one hour, to kill the 
bacteria; now we proceed to standardize the vaccine; i. e., 
to determine how many bacteria we have there per cubic 
