PYOGENIC BACTERIA. 375 
ment can only be followed for two or three days. Upon potato, ata 
temperature of 35° to 37° C., a rather thick, moist layer of consider- 
able extent forms at the end of twenty-four to forty-eight hours ; 
this is also at first of a pale-yellow, and later 
of an orange-yellow color. The temperature 
mentioned is most favorable for the rapid 
development of this micrococcus, although 
multiplication may occur at a comparatively 
low temperature and is tolerably abundant at 
the ordinary room temperature. 
Cultures of the ‘‘ golden staphylococcus,” 
and especially those upon potato, give off a 
peculiar odor which resembles that of sour 
paste. When cultivated in milk it gives rise 
to the formation of lactic and butyric acids 
and to coagulation of the casein. No poison- 
ous ptomaines or toxalbumins have been iso- 
lated from cultures of this micrococcus, but, 
like other liquefying bacteria, it forms a sol- 
uble peptonizing ferment, by which gelatin 
may be liquefied independently of the living 
microérganism. While the Staphylococcus 
aureus gives rise to the production of acids— yg ¢0.—Gelatin culture of 
principally lactic acid—in media containing Staphylococcus pyogenes aureus 
glucose or lactose, it has also been shown by @*uméa"e™- 
Brieger that ammonia is one of the products of its vital activity. 
Unlike some other pathogenic bacteria, it is able to grow in a medium 
having a distinctly acid reaction. A non-poisonous basic substance 
has been isolated by Brieger from old cultures in meat infusion which 
differs from any of the ptomaines obtained by him from other sources. 
The thermal death-point of this micrococcus, in recent cultures in 
flesh-peptone-gelatin, as determined by the writer, is between 56° and 
58° C., the time of exposure being ten minutes. When in a desic- 
cated condition a much higher temperature is required—0° to 100° C. 
—for its destruction ; and it retains its vitality for more than ten 
days when dried upon a cover glass (Passet). It retains its vitality 
for a long time in cultures in nutrient gelatin or agar, and may grow 
when transplanted from such cultures even at the end of a year. 
Very numerous experiments have been made to determine the 
proportion of various chemical agents required to destroy the vitality 
or to restrain the growth of this important pyogenic micrococcus. 
The extended researches of Liibbert (1886) with reference to the 
antiseptic power of agents added to a suitable culture medium—nu- 
trient gelatin—gave the following results: Development was _ pre- 
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