PLATES 6 ZO i0The monkey has been employed in only a few instances for the investigation of experimental pneumococcic pneumonia. Among the reported studies, in which this animal was used, those of Blake and Cecil (I) and SchSbl and Sellards (2) give detailed observations concerning the pathology and pathogenesis of the disease. Stuppy, Falk, and Jacobson (3) were concerned principally with the production of Type I pneumococcus pneumonia in the Macacus rhesus and Cebus capucinus species. Francis and Terrell (4) studied the production and clinical course of Type III pneumococcus pneumonia in the Java monkey , Macazus cynomolgos. They used both the intratracheal and intrabronchial methods of inoculation. With the intratracheal method it was noted that the inoculum was more widely distributed in the lungs than when the intrabronchial procedure was employed. Similar lesions, as observed by x-ray, eventually developed, however, following either technique of production.Blake and Cecil used the intratracheal method of inoculation during their studies and concluded that the resulting pneumonic infection simulated in every way that which occurred spontaneously in man. Concerning the mechanism of lobar consolidation, they, further, concluded that the pneumococci penetrated directly through the epithelium of the main bronchus of the lobe near the hilum and spread rapidly throughout the lobe by way of the perivascular and peribronchial tissues and lymphatics into the alveolar walls where they then passed into the air spaces simultaneously with the outpouring of the exudate. More recently Robertson and coworkers (5-7), Gunn and Nungester (8), Wood (9), and the author (10), using the intrabronchial method of inoculation and different animal species, also noted the similarity between the experimental pneumococcic infections and those which occur spontaneously in man, but their findings did not support those of Blake and Cecil, concerning the manner by which the organisms spread within the lungs. Rather they confirmed the views of Loeschcke (11) who concluded, from his studies of the pathogenesis and pathology of the pneumococcic pneumonia in man, that the pneumonic process was primarily intraalveolar and intrabronchial, and that the pneumococci were carried in the edema fluid directly from alveolus to alveolus through the pores of Kohn (12) and from bronchiole to bronchiole as a result of repeated aspirations, aided by breathing, coughing, and gravity.