We have observed evidence of organization in its earlier reactions taking place in the patches of gray consolidation. This organization of the lung tissue takes place as an interstitial fibrosis and as an alveolar organization. Masses of granulation tissue grow out into and come to occupy the lumen of the air sacs, while in other instances the new growth of tissue takes place mainly in the alveolar walls converting them from thin partitions to thickened and tough structures. In the cases in which a purulent pneumonia was present for some time, and where some of these tended towards repair, this type of restoration with the new development of connective tissue was found. The amount of fibrosis varied very much, and in many instances there was no evidence that obstruction to the bronchioles occurred to a material degree. Hence, although we believe that more or less organization occurs in all of those cases which have passed through a purulent pneumonia, and that a permanent mark is left upon the lung tissue, it is not probable that the amount of involvement and final damage by fibrosis is sufficient to seriously influence the pulmonary respiration. There is, however, a certain percentage of cases in which this organization and fibrosis does involve sufficient of the lung parenchyma and bronchioles to interfere with the pulmonary ventilation. Where the purulent pneumonia has markedly involved the parenchyma, and particularly where vascular channels both large and small have suffered, some of them by thrombosis, others by a sclerotic thickening, the circulatory disturbance may be sufficiently interfered with to infarct the area. The infarction usually occupies the purulent area itself, and with the complete occlusion of the circulation the resulting necrosis gives rise to an appearance different from that usually seen in pulmonary infarcts. The area may lie in the peripheral portion of the lobe or may occupy deeper parts. The infarct is of a cream-white color, quite homogeneous, and resembles the appearance of a local area of caseous pneumonia. This appearance is brought about through the local purulent consolidation undergoing necrosis. Some of these areas rapidly develop a cavity through liquefaction of the exudate.