MICROCOCCUS TETRAGENUS 93 



Motility. Non-motile. 



Staining Reactions. It stains easily with the ordinary aniline dyes, 

 but not by the Gram method. 



Biological Characters. It is aerobic and facultative anaerobic, 

 growing both at ordinary room and incubator temperatures. 



On Gelatine Plates it forms small elevated porcelain-like clusters ; the 

 gelatine is not liquefied, but eventually acquires a brownish colour. 



hi Gelatine Stab Cultures a typical nail-shaped growth occurs. 



On Agar Media it forms a whitish coating. 



On Potatoes it develops a yellowish-white coating which contains gas 

 bubbles at incubator temperature. 



Media containing grape sugar undergo fermentation, Co 2 , H., ethylic 

 alcohol, and acetic acid being formed. 



Milk is not coagulated. 



Vitality. At 40 C. development ceases, the thermal death-point 

 being about 56 C. The bacilli retain their vitality in ordinary culture 

 media for a long time, living for several months. 



Pathogenesis. The bacillus of pneumonia is pathogenic for mice 

 and dogs, and slightly so for guinea-pigs. It is distinguished 

 from the diplococcus of pneumonia by rabbits being immune. Sus- 

 ceptible animals are inoculated direct into the pleural and abdominal 

 cavities. They can also be affected by inhalation of dried pulverized 

 cultures. In some cases pneumonic lesions are formed. 



MICROCOCCUS TETRAGENUS. 



This micrococcus was discovered by Koch in 1884 in a phthisical 

 lung cavity. Gaffky made a further study, and described its patho- 

 genic peculiarities for various experiment animals. Biondi also 

 found it in human saliva. 



Microscopical Appearances. When obtained from the animal 

 body it occurs mostly in groups of four surrounded by a capsule. 



Motility. Non-motile. 



Staining Reactions. It stains by the Gram method, the proto- 

 plasm remaining stained while the capsule is decolorized ; also with 

 the ordinary aniline dyes. 



Biological Characters. It grows best in the presence of oxygen 

 on the usual media at from 35 to 38 C., and also at 20 C. 



On Gelatine Plates white, shiny, prominent, round colonies develop. 



In Gelatine Stab Cultures it grows on the surface as well as along the 

 track of the needle ; on the surface it forms a white, shiny exuberance. 

 The gelatine is not liquefied. 



