416 PATHOGENIC MICROCOCCI 



of agar, at 37 C., a grayish- white or yellowish layer is formed at the end of 

 twenty-four hours, which has a varnish-like lustre. Upon potato, at 30 to 

 35 C., at the end of forty-eight hours a white or yellow layer has de- 

 veloped. 



Pathogenesis. According to Heydenreich, inoculations in rabbits, dogs, 

 chickens, horses, and sheep cause a skin affection which is identical with 

 that which characterizes Biskra button in man. When rubbed into the 

 healthy skin of man it also produces the development of abscesses. 



MICROCOCCUS ENDOCARDITIDIS RUGATUS (Weichselbaum). 



Obtained by Weichselbaum (1890) from the affected cardiac valves in a 

 fatal case of ulcerative endocarditis. 



Morphology. Micrococci, resembling the staphylococci of pus in dimen- 

 sions and mode of grouping; solitary, in pairs, in groups of four, or in ir- 

 regular masses. 



Biological Characters.- An aerobic micrococcus. Does not grow at the 

 room temperature. Upon agar plates, at 37 C. , at the end of three or four 

 days the superficial colonies consist of a small, brown, central mass sur- 

 rounded by a granular, semi- transparent, grayish marginal zone; gradually 

 they attain a characteristic wrinkled appearance ; the deep colonies, under a 

 low power, are irregular, finely granular, and contain a large central, yel- 

 lowish-brown nucleus surrounded by a narrow, grayish-brown peripheral 

 zone. In agar stab cultures small, spherical colonies are formed upon the 

 surface, which become confluent, forming a grayish-white, wrinkled layer 

 which has a stearin-like lustre and is very viscid ; a scanty growth occurs 

 along the line of puncture. Upon potato, at 37 3 C , a scanty development 

 occurs in the form of a small, dry, pale-brown mass. Upon blood serum 

 isolated or confluent, colorless colonies are formed the size of a poppy seed ; 

 these are closely adherent lo the surface of the culture medium. 



Pathogenesis.- Wben injected subcutaneously into the ear of a rabbit it 

 produces tumefaction and redness; in guinea-pigs, formation of pus. When 

 injected into the circulation of dogs, after injury to the aortic valves, an en- 

 docarditis is developed. 



MICROCOCCUS OF GANGRENOUS MASTITIS IN SHEEP. 



Obtained by Nocard (1887) from the milk of sheep suffering from gan- 

 grenous mastitis (rnal de pis or d'araignee), a fatal disease which attacks 

 especially sheep which are being milked for the manufacture of cheese, at 

 Roquefort and elsewhere in France. 



Morphology. Micrococci, solitary, in pairs, or in irregular groups, resem- 

 bling the staphylococci of pus in dimensions and arrangement. 



Stains with the usual aniline colors and also by Gram's method. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing micrococcus. Grows at the room temperature in the usual culture me- 

 dia. Upon gelatin plates, at the end of forty-eight hours, the colonies are 

 spherical and white in color; under a low power the superficial colonies are 

 circular in outline, homogeneous, and brown in color ; they are surrounded 

 by a semi-transparent aureole ; liquefaction around the superficial colonies 

 occurs sooner than around those beneath the surface of the gelatin. In i 

 gelatin stick cultures, at 18 to 20 C., on the second day liquefaction of the! 

 gelatin commences near the surface ; by the fifth day a pouch of liquefied ' 

 gelatin has formed, which has the shape of an inverted cone; at the bottom 

 of this an abundant deposit of micrococci is seen, while the liquefied gela- 

 tin above is clouded throughout. In agar stick cultures development oc- 

 curs upon the surface as a thick white layer, which gradually extends 

 over the entire surface, and after a time acquires a yellowish tint ; develop- 

 ment also occurs along the line of puncture. Upon potato a thin, viscid, 

 grayish layer is slowly developed ; the outline is irregular and the edges 

 thicker than the central portion ; the central portion of this layer gradually 



