64 



MASTITIS OF THE COW 



aerobically and anaerobically, but better aerobically. It alsp 

 grows well on the common culture media without serum. 



In serum-gelatin-agar plates at 38° C. the growth is 

 distinct after one day. After two days sparse deep coloriies 

 form in the last plate which are the size of a pinhead, 



Fio. 15. — Deep colonies of colon bacilli with and without daughter colonies. Serum-gelatilt- 

 agar plates. T. 3S° C, 2 days (X 30). 



yellowish-white, round points which are not infrequently 

 surrounded by one or more broad, grayish-white zones. 

 This zone is produced in the cultui'e media by the bacilli 

 which wander out from the colony. The zone can therefore 

 be called the " wander zone." 



Under the microscope the colonies are almost trans- 

 parent, yellow, round or rounded and have 

 an even or coarsely crenated margin. 



The colonies with "wander zones" show 

 a large colony in the middle, the mother 

 colony, which is surrounded by a more or 

 less broad ring of peripheral or daughter 

 colonies. These colonies present growing 

 margins depending upon the outwandering 

 of bacilli (Fig. 15). 

 The surface colonies are numerous and form bright gray 

 round or irregularly lobed thin coverings from 6 to 10 mm. 

 Under the microscope they often show a granular centre 

 which depends upon the formation of the colonies in the 

 media (Fig. 16). In stab cultures in gelatin-agar (Fig. 

 17) , agar at 38° C, and gelatin at 20° C. the colonies form 



Fia. 16.— Surface 

 oolony of colon bacilli. 

 Serum - gelatin - agar 

 plates. T. 38° C, 2 

 daysCX 10). 



