(A) Lesions of the Hematopoietic System. (B) Lesions of the Vascular System, Parenchymatous Organs, Alimentary Tract, and in the Walls of Other Hollow Viscera. (C) Miscellaneous Lesions. IV. Comparison between the Respiratory Lesions of Influenza and those Initiated by the Inhalation of Poisonous Gases with Special Reference to:— (A) The Inflammatory Response versus the Systemic Capacity to Compensate. (B) The Primary Injury. (C) The Tendency to Organization of Bronchiolar and Alveolar Exudates with Bronchiolitis and Bronchiolectasis as Sequelæ. (D) The Importance of the Trachea and its Ramifications as a Protective Mechanism against Infection of the Pulmonary Parenchyma. V. Peculiarities of the Histology of Influenzal Pneumonia. (A) The Extent of the Initial Pulmonary Lesion. (B) The Hemorrhagic Exudate—The Relation of Red to Grey Hepatization. (C) The Aplastic Exudate. (D) The Hyaline Necrosis of the Pulmonary Tissue. (E) The Organization Process. VI. Infection as a Possible Etiological Factor for Malignant New Growths. VII. The Bacteriology of Influenzal Pneumonia. (A) Organisms Associated with Influenzal Pneumonia. (B) The Relation of the Type of Organism to Pleural Involvement. (C) The Relation of Different Organisms to the Type of Pneumonia. (D) Summary and Discussion. VIII. Conclusions. IX. Bibliography. X. Illustrations. [Illustration: FIG. III. AUTOPSY NO. 90. DRAWING FROM A LESION OF THE TRACHEA (SOMEWHAT OLDER THAN THAT ILLUSTRATED IN FIGURE II). THE MUCOSA IS ENTIRELY LACKING. CONGESTION AND EDEMA ARE THE STRIKING FEATURES IN THE SUBMUCOSA. THE NECROTIZING PROCESS HAS EXTENDED INTO THE MUCUS GLANDS. THIS IS SHOWN IN THE LOWER PICTURE. ] [Illustration: FIG. IV. AUTOPSY NO. 205. CONGESTION AND EDEMA OF THE SUBMUCOSA AND REGENERATION OF THE TRACHEAL EPITHELIUM. ] [Illustration: FIG. VII. AUTOPSY NO. 94. A NECROTIZING PROCESS LIKE THAT OF THE TRACHEA ILLUSTRATED IN FIGURE II. HERE IT IS SHOWN TO INVOLVE THE WALL OF THE BRONCHIOLE. ] [Illustration: FIG. V. AUTOPSY NO. 95. AN EARLY LESION OF THE BRONCHIOLE CHARACTERIZED BY HYALINIZATION OF THE EPITHELIUM AND SEROUS EXUDATE IN THE LUMEN. ] [Illustration: FIG. VI. AUTOPSY NO. 103. ILLUSTRATES ANOTHER EARLY BRONCHIOLAR LESION. THE EPITHELIUM IS LACKING, THE CONGESTED VESSELS OF THE SUBMUCOSA PROTRUDE INTO THE LUMEN WHICH CONTAINS DESQUAMATED EPITHELIUM, MUCUS, AND RED BLOOD CELLS. ] PATHOLOGY OF INFLUENZA THE PATHOLOGY OF THE RESPIRATORY TRACT IN INFLUENZA