Hemolytic streptococci produce more or less severe inflammations of the udders of cows. Frequently infected quarters are swollen, firm, hot, and tender. In a number of instances it has not been possible to detect gross changes in the mammary gland.

The streptococci isolated from the invaded quarters have produced clear zones of hemolysis immediately surrounding the colonies when cultivated in horse blood agar plate cultures. The hemolytic zone has varied from a clear, narrow band up to zones 1.7 to 2 mm. wide.

When the streptococci are classified according to their action upon carbohydrates, they fall into two broad groups: the larger consists of nineteen strains fermenting dextrose, lactose, saccharose, maltose, and salicin; and a smaller number comprising ten species produces acid in dextrose, lactose, saccharose, and maltose and fails to ferment salicin. One of the non-salicin-fermenting strains did not attack saccharose. In no instance was acid production noted in raffinose, inulin, or mannite.

All streptococci except three were agglutinated by an antiserum obtained from a rabbit immunized with a single strain.

Freshly isolated cultures when injected intravenously into rabbits possess but slight pathogenicity. Localizations in the joints occurred in two instances. The others either failed to affect the general condition of the animals or produced only a slight febrile reaction.

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