I7S PRACTICAL BACTERIOLOGY. 



cultivation has developed in a characteristic way ; no 

 thread forms along the track of the needle, but in its 

 place a number of very small completely globular 

 colonies are to be seen, often only ^ to 5 mm. in 

 thickness ; they are quite isolated from one another, 

 and even if the cultures are kept for a long time, 

 show no inclination to coalesce. They are white, and 

 along the whole length of the track are of approxi- 

 mately uniform size, thus showing that here again 

 we are dealing with a facultative anaerobe. This 

 peculiar mode of growth in gelatine is most character- 

 istic of the Streptococcus pyogenes ; there are, it is 

 true, some other forms, which behave in a similar 

 manner, but they are, comparatively speaking, rare, 

 and hence of slight practical importance; we shall 

 therefore omit to speak of them altogether. The 

 strong likeness between the Streptococcus of erysipe- 

 las, and the Streptococcus pyogenes, has already been 

 mentioned ; the puncture culture of the one in gelatine 

 is not to be distinguished from that of the other. 



In a stroke cultivation of the Streptococcus pyo- 

 genes a thin transparent film is formed, similarly 

 composed of small colonies, which do not readily 

 coalesce, and which do not extend much beyond the 

 stroke. In this case also, the organisms multiply 

 but slightly, and in a short time the growth of the 

 colony ceases. If the cultivations be made on agar- 

 agar, and the temperature be raised to blood heat. 



