42 STUDY AND IDENTIFICATION OF BACTERIA. 



STREPTOCOCCUS FORMS. 



Those cocci tending to arrange themselves in chains are usually 

 described as streptococci. When we consider that certain bacilli at 

 times assume an arrangement which we term strepto-bacilli, yet have 

 no relationship, it would suggest that the matter of chain morphology 

 is simply a characteristic common to many entirely different cocci. 



The essential point to bear in mind is that the finding of a strepto- 

 coccus does not necessarily explain an infection, because normally 

 streptococci are among the organisms most frequently and abundantly 

 found in plates made from normal buccal and nasal secretions. It is 



FIG. ii. Streptococcus pyogenes. (Kolle and Wassermann.) 



well to be very conservative when reporting streptococci as the etiologi- 

 cal factor from lesions of the throat or nose. 



Probably the most practical point in the differentiation of strepto- 

 cocci, next to that of pathogenicity, is the occurrence of long or short 

 chains, the virulent ones tending to appear in chains of from ten to 

 twenty cocci, while the normal inhabitants of the nose, mouth and 

 feces generally tend to be in shorter chains. 



As regards virulence, this is exceedingly variable it is soon lost, but 

 may be restored either by inoculating streptococci along with various 

 other organisms or by passage through successive rabbits. The rabbit 

 is the most susceptible animal and should be inoculated in one of the 



