SECTION II. 
PATHOGENIC BACTERIA. 
CHAPTER XII. 
THE PYOGENIC COCCI. 
The Bacteria of Inflammation. 
The Staphylococcus Group. 
Micrococcus Aureus. 
Staphs lococcus Pyogenes Citrous. 
Staphylococcus Pyogenes Alhvis. 
Staphylococcus Epidermidis Albus. 
Micrococcus Tetragenus. 
Micrococcus Ovalis. 
THE BACTERIA OF INFLAMMATION. 
There is a group of bacteria which possesses in common the ability 
to incite that type of infection which is commonly spoken of as inflam- 
mation. A majority of these organisms are habitual parasites of man 
living upon the exposed surfaces of the body, the skin and mucous 
membranes chiefly; with respect to their pathogenic properties they 
may be regarded as "opportunists," not as a rule requiring a well- 
defined portal of entry through definite tissues to become invasive. 
Any break in the continuity of the skin or a weakening or change in 
the physiological state of a mucous membrane (frequently caused by 
intracurrent infection) provides the necessary atrium for invasion of 
the underlying tissues. 
Not only are these bacteria ordinarily unable of themselves to locate 
and force an entrance to the tissues of their host; after invasion is 
accomplished they are unable to escape from the tissues in sufficient 
numbers to cause progressive disease of like nature in other hosts. 
They are locked up in the body, as it were, and eventually perish. 
They have not perfected their pathogenic mechanism. (See chapter 
on Parasitism.) 
Bacteria of the "opportunist" type may be raised to very con- 
siderable pathogenic powers if artificially' created atria of entrance to 
and escape from the tissues are provided, as for example, by passage 
through suitable animals, but they soon tend to lose their artificially 
acquired pathogenic properties under ordinary conditions and return 
again to a parasitic existence. 
Prominent among these habitually parasitic bacteria which occur 
on the skin and mucous membranes of man are various members 
of the Staphylococcus and Streptococcus Groups. 
