468 BACTERIOLOGY. 
Occurrence in Man. The staphylococcus -pyogenes 
aureus is the commonest pyogenic micro-organism found 
in man. From the fact that these micrococci are so 
constantly present in the pus of acute abscesses, as de- 
monstrated by Ogston, Rosenbach, Passet and others, 
it was formerly assumed that there could be no pus- 
formation in the absence of micro-organisms of this 
class; but it is now well known, from the experiments, 
that certain chemical substances, such as nitrate of 
silver, oil of turpentine, strong liquor ammoniz, etc., 
introduced beneath the skin, give rise to pus-formation 
quite independently of bacteria. Practically all micro- 
organisms, moreover, have been shown by experiment to 
produce under certain conditions the formation of pus 
by their products when inoculated into the animal body; 
but, while this has been demonstrated, the extended 
researches of bacteriologists show that few species are 
usually concerned in the production of acute abscesses, 
furuncles, etc., in man. Of these the two most im- 
portant, by reason of their frequent occurrence and 
pathogenic power, are staphylococcus pyogenes aureus 
and streptococcus pyogenes; next to these comes the 
staphylococcus pyogenes albus. Two or more species 
are often found in the same abscess; thus, Passet, 
in 33 cases of acute abscess, found staphylococcus 
aureus and albus associated in 11, albus alone in 4, 
albus and citreus in 2, streptococcus pyogenes alone in 
8, albus and streptococcus in 1, and albus,. citreus, and 
streptococcus in 1. 
As the result of extended researches, however, made 
by bacteriologists within recent years the golden staphy- 
lococcus has been demonstrated not only in furuncles 
and carbuncles, but also in various pustular affections 
