Pneumococcus Type 37, like pneumococcus Type 3, is characterized by the production of large mucoid colonies on the surface of solid media and by its very large capsule. It differs from the highly virulent pneumococcus Type 3 in that it is only slightly virulent for mice and rats and is isolated infrequently from man. A study of the behavior of pneumococcus Type 37 in systems comparable to those used in the study of pneumococcus Type 3 and an examination of the chemical structure of the capsule of pneumococcus Type 37 are described VSports手机版. The capsular polysaccharide of pneumococcus Type 37 is a viscous, optically inactive polymer composed of 95% hexose. Glucose is obtained in 88% yield upon acid hydrolysis. Periodate oxidation studies and the behavior of the polysaccharide on acid hydrolysis suggest that the molecule consists of a core of repeating units of 1,3 glucosyl-glucose to which short chains of glucose are attached at frequent intervals. Isolation of a disaccharide, the properties of which are identical with those of sophorose (beta1 --> 2 glucosyl-glucose), and of a trisaccharide are described. A tentative structure for the capsular polysaccharide of pneumococcus Type 37 is proposed. .