The other process by which insular pneumonia develops seems to begin in the septa of the smaller alveoli and in the perivascular areas. This has been looked upon as hematogenic or pleurogenic. The first change occurs in the surroundings of the primary alveoli where there appears a richness of nuclei, of round, moderately well stained character, among which one may see a few granular and red blood cells. Soon the epithelia of adjacent alveoli increase in number and a fibrinocellular exudate appears, at first probably in the smaller sacs. However when the lesion is intensive the course of events must be rapid for the identity of a group of primary alveoli is soon lost and the exudate may extend to the larger air space. (Fig. 11) In severe or late cases a decision as to the course of origin is often impossible. The most instructive point of this part of the study is the closing of primary alveoli by the swelling of their septal ends and the early occlusion of the secondary alveolus by a catarrhofibrinous or even pus-like material. It is quite possible that a similar course of events transpires in the pathogenesis of human pneumonia, the superficial avian form being comparable to the aspiration form, the interstitial form comparable to the septicemic variety. ABSCESS AND GANGRENE OF LUNG. Abscess and gangrene of the lung are degenerative processes dependent upon embolism, or inspiration of infective matter and it is usually assumed that gangrene succeeds upon abscess when the blood or air supply of a part of the pulmonary tissue has been obstructed mechanically or by inflammation. A review of our material adds little to the etiology or pathogenesis of these two lesions, well recognized as they are by veterinarians. As opposed to human beings, lower animals probably suffer more from them, for an explanation of which one can probably look to the B. necrosis or necrophorus, an organism quite common in feed, and acknowledged to be of great importance as a secondary invader during specific infectious diseases. It has been found in embolic abscesses and in the organs in calf diphtheria and similar other conditions. It has been cultivated here twice, once from a lung abscess, once from Kangaroo disease. It doubtless occurs in human necrotizing processes but is seldom emphasized or even heard about; possibly none is due to it or its congeners. TABLE 10. _Table giving Analysis of 20 Mammalian and 3 Avian Cases of Abscess and Gangrene of the Lung_