248 MILK AND ITS HYGIENIC RELATIONS 



him in all the samples examined and in all stages of handling of 

 the milk. 



Heinemann (2) also found that Streptococcus lacticus becomes 

 more virulent by passage through rabbits, and after five passages 

 may become equal in virulence to Streptococcus pyogenes. The 

 same culture, after it had been increased in virulence by passage, 

 proved fatal to an animal, which showed no symptoms on being 

 inoculated with a dose of the same strain before passage. 



More definite results have been obtained by studying the 

 appearance of the organisms. 



The chain formation has been shown to have variable 



characteristics. Some samples have long chains, others short 



chains, and in some c cases an ill-defined capsule is present. The 



long and short chain varieties are shown in the accompanying plate. 



(See Plate II.) 



Ernst believes that with experience it is possible to determine 

 the presence of the pathogenic varieties of streptococci with a high 

 degree of certainty. He says : ' The streptococcus acquires a 

 diplococcic formation, the cocci appear to press one another, 

 become disc-shaped, and appear linear in profile. They lie on a 

 different axis from that of the chain. A more or less pronounced 

 capsule is formed around the streptococci of " animal " origin, 

 which may expand to a broad mucin capsule.' The presence of this 

 variety is regarded by Ernst as denoting mastitis. (Cp. Plate III.) 



Trommsdorff agrees with Ernst, and thinks that in the early 

 stages of mastitis the short diplococcic forms are found in the 

 sediment, passing to the long chain formation in later stages. 



Gminder also showed that the streptococci appearing in milk 

 when mastitis is present appear rather to have the form of flattened 

 diplococci than of the usual chain. These characteristics may, 

 however, also be shown by saprophytic strains outside the organism. 

 Saprophytic forms, when injected into the udder, tend to become 

 pathogenic. No precise morphological characteristics in the two 

 varieties were determined, but Gminder considers that where a 

 milk sediment is found to contain streptococci showing the peculiar 

 form above mentioned, further investigations should be carried 

 out. He considered that there was no connection between the 

 virulence of the strain and the production of haemolysis. 



Similar appearances in the streptococcic formations were 

 found by Rosenow and Davis, in connection with a milk-borne 

 epidemic in Chicago, and by Hamburger in Baltimore. 



Rosenow and Davis found that the streptococci which were 

 isolated from this epidemic showed a weak capsular substance 

 surrounding the streptococci. The capsule was not indented and 

 was lost on culturing. The strains were pathogenic to mice and 

 rabbits, killing them within twelve to twenty-four hours. Virulence 

 was increased by passage, as was also the definition of the capsular 

 substances. 



