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From a bacteriological study of 137 strains of streptococcus agalactiae, it seems that this species is perfectly defined by bacteriological tests, the most characteristic of which is hydrolysis with hippuric acid. The brown pigment of the strains, the conditions for demonstration of which are described and discussed here, may also be an important characteristic for it is rare in streptococci. The pigment was extracted, its nature and role are discussed. The sensitivity to 12 antibiotics was studied; the beta-lactamines were the most commonly active.

Streptococcus agalactiae, Streptococcus faecalis, Staphylococcus aureus, Escherichia coli, and Corynebacterium bovis were examined for their ability to adhere to the ductular epithelial cells of the bovine udder. S. agalactiae and S. aureus adhered readily and in large numbers, whereas the other organisms adhered poorly or not at all. The organisms showing the ability to adhere are those which frequently cause mastitis. These data suggest that selective adherence to the ductular epithelium may be the first stage in the pathogenesis of streptococcal and staphylococcal mastitis.