PYOGENIC BACTERIA. 



375 



ment can only be followed for two or three days. Upon potato, at a 

 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 

 microorganism. While the Staphylococcus 

 aureus gives rise to the production of acids 

 principally lactic acid in media containing Staphylococcus pyogenes aureus 

 glucose or lactose, it has also been shown by ( 



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 90 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 Lubbert (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- 



FIG. 80. Gelatin culture of 



