PATHOGENIC BACTERIA 155 



Agglutination. On the fourth day; in dilution of i : 50 

 agglutination is bad. 



Protective Serum. Flexner has been able to obtain an anti- 

 toxin from monkey serum that has therapeutic properties in 

 man. 



Micrococcus Tetragenus (Koch; Gaffky). Origin. 

 Koch found this microbe in the cavity of a tuberculous lung. 

 Gaffky, in 1883, studied its pathogenic actions and gave it the 

 name it now bears. 



Form. Cocci which are gathered in the tissues in groups of 

 four, forming a square a tetrad. (See Fig. 90.) In artificial 



^-^r 



Fig. 90. Micrococcus tetragenus in sputum (tubercle bacillus also). 



culture sometimes found in pairs. A capsule of light, gelati- 

 nous consistence surrounds each tetrad. 



Properties. They are immobile; do not liquefy gelatin. 



Growth. They grow well on all nutrient media at ordinary 

 and brood temperatures; are facultative aerobic. They grow 

 slowly. 



Colonies in gelatin plates. In two days, little white spots, 

 which, when on the surface, form little elevations of a porcelain- 

 like appearance; under low power they are seen very finely 

 granulated. 



Stab-culture. Small round separated colonies along the 



