In many cases of diphtheria the exudation extends down the bronchi even to their finest ramifications, and sometimes also to the lung alveoli. The bronchi contain casts which do not generally obstruct the calibre entirely. These casts consist of fibrine and leucocytes, the latter in great abundance. Sometimes the finer bronchi generally are filled with leucocytes. There is also exudation of leucocytes into the air vesicles, but not usually of fibrine. This extension is from the penetration of the bacillus diphtheriae into the lungs. Although there is a great exudation of leucocytes these do not englobe the bacilli as they do the pneumococcus. The bacillin diphtherial is taken up by the epithelium of the alveoli (Flexner and Anderson).