EXAMINATION FOR STREPTOCOCCI 153 



the results of further experiments on the pathogenicity of Str. 

 lacticus and these in general confirm his earlier work. Two 

 strains, one only of which was hsemolytic, but both capable of 

 fermenting a variety of the usual test substances, were exalted 

 in virulence by animal passage, and it is important to note that 

 the fermentative capacity gradually decreased until finally one 

 strain fermented only dextrose, and the other dextrose and 

 saccharose. The non-hsemolytic strain became hsemolytic and 

 both showed an increased tendency to chain formation. From 

 these results Heinemann suggests that the determination of the 

 fermentative ability of the streptococci might be of value in 

 determining the previous environment of the organisms. If 

 in contact with an animal lesion a low fermentative capacity 

 would result whilst a high capacity would indicate a medium 

 rich in carbohydrates. 



Although the questions of the variability of streptococci 

 in mastitis and the relation of mastitis to septic sore throat, 

 are still far from being satisfactorily solved, it has been fairly 

 definitely established that the great majority of the strep- 

 tococci ordinarily found in milk are non-pathogenic and do 

 not indicate a pathological condition of the udder. Str. lac- 

 ticus, which may be found in almost every sample of milk, is 

 used industrially in cheese manufacture and is also employed 

 as a therapeutic agent. This streptococcus is typical of the 

 group characterised by high fermentative capacity and low 

 pathogenicity. The pathogenic streptococci, on the other 

 hand, ferment but few of the Gordon test substances and pro- 

 duce low acidities in the media that are fermented; the mor- 

 phological appearance is characterised by the picket fence 

 (stalkett) formation but the chain may be either short or long; 

 haemolysis is marked. 



Examination for Streptococci. Probably the most satis- 

 factory method of examination for excessive numbers of strep- 

 tococci resulting from mastitis, "is the direct miscroscopical 

 method of a smear prepared either by the Stewart-Sloan method 

 described on page 126 or the Breed method described on page 



