INDIVIDUAL FEATURES OF PYOGENIC BACTERIA. 113 



variable effects. The germ usually kills the animal, causing 

 a rapid general septicaemia ; at other times the animal reacts 

 only slightly. Subcutaneously it causes erysipelas and the 

 formation of abscesses. All laboratory animals are susceptible 

 to infection by means of the Streptococcus pyogenes. Birds seem 

 to be immune. 



V. Micrococcus Tetragenus. 



The Micrococcus tetragenus was obtained by Koch a. from 

 cavities of tuberculous lungs, b. in the sputum of phthisical 

 patients in the last stages of the disease, c. in the pus of 

 buccal and d. ocular abscesses. It has been found by Morinier 

 e. in the normal saliva and /. even in the saliva of newborn 

 babes. 



Morphology. A micrococcus with a diameter of about 1 

 mikron, formed in groups of 8 (tetrads) and enveloped by a 

 transparent gelatinous substance. 



Principal Biologic Properties. It is a facultative anaerobic. 

 It grows on all ordinary culture-media. Milk is coagulated 

 with acid formation. On agar it forms thick, granular spher- 

 ical colonies of a white or grayish color. It does not liquefy 

 gelatin. It stains with all the anilin dyes and readily by 

 Gram's method. 



Pathogenesis. When inoculated into guinea-pigs subcutane- 

 ously, the animals die rapidly and abscesses are formed at the 

 point of inoculation. The micrococcus at the autopsy may 

 be found in all the organs and in the blood taken from the 

 heart. 



GONORRHCEA. 

 VI. Micrococcus Gonorrhceae (Gonococcus). 



Discovered by Neisser in 1879, the gonococcus causes the 

 specific suppuration of gonorrhoea. 



Pathogenesis. This micrococcus, or diplococcus, as it is 



generally called, has a special affinity for the urethral mucous 



membrane, finding lodgement in the epithelial cells lining 



this canal. It very often causes inflammation with or with- 



8 M. B. 



