Bacteriologic examination demonstrates the presence of hemolytic streptococci in the blood of the heart; plates from the left lung contain a few colonies of S. aureus and Pneumococcus IV; plates from the right main bronchus contain S. aureus and a large bacillus which does not stain by Gram’s method. Three plates from the spinal meninges contain Pneumococcus IV. [Illustration: Fig. 25.—Advanced bronchiectasis throughout lower left lobe. Autopsy 445. ] Microscopic examination shows that the cavities which have been described are lined by very vascular connective tissue containing many cells; there is no epithelial lining and the surface is in places covered by fibrin. On the surface polynuclear leucocytes are numerous, but immediately below, large mononuclear cells occur and frequently contain one or several ingested polynuclear leucocytes. None of the structures peculiar to the bronchi can be identified in the wall of these cavities, and in many places it is evident that lung tissue has undergone destruction, for in places the lining of vascular connective tissue is interrupted and an extension of the cavity penetrating into the lung substance is surrounded by alveoli filled with fibrin; in contact with the cavity there is some necrosis. The cavities communicate with the bronchi and are lined in part by vascular connective tissue which may in part represent preexisting bronchial walls, but no epithelium is present and the relation to the bronchi cannot be established with certainty. These cavities have extended by necrosis which has broken the vascular connective tissue of their wall and penetrated into adjacent lung tissue. Death has been the result of purulent meningitis caused by pneumococcus, and the histologic changes in the walls of the cavities suggest that the activity of the inflammatory reaction here is subsiding, for large mononuclear cells are numerous and are ingesting polynuclear leucocytes. The changes described would, if continued, result in the formation of cavities lined by fibrous tissue and resembling many of those formed as the result of dilatation of the bronchi.