CONSIDEKABLE attention has lately been directed to the bacteria which are to be found in bronchitic secretion, and, although various writers have assigned an important etiologioal relationship to some of these bacteria, yet the infective nature of bronchitis ha6 not hitherto been generally accepted. The object of the present article is to give a short abstract of the inore important literature dealing with this subject, and to record the main results of some original investigations, undertaken

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... n order to ascertain, if possible, what are the bacteria causing acute bronchitis. A study of the infective nature of bronchitis is so closely associated with that of the bacteriology of the normal air passages, that it is important to know whether the lower air passages-trachea. bronchi, and pulmonary alveoli-normally contain bacteria, and, if so, whether these bacteria are pathogenetic. There are, on the one hand, authorities-such as J~aumgarten (I) and Hoffmaim (2)-who assert that the lower air passages normally contain bacteria, the latter stating that Streptococcus pyogenes, Staphylococcus ppyenes aureus, pneumococcus, etc., exist in the bronchi of healthy individuals without causing harm. Pamieri (3) and Durck ( 4 ) hold similar opinions. Durck examined the healthy lungs of t l e human subject in thirteen cases, and found the Diplococc~~ pneumonin! twelve times, and also streptococci, staphylococci, pneumo-bacilli, and Bacterium coli conamme. Examining the lungs of ten pigs, he found pneumo-bacilli eight times, and in the lungs of healthy horses and cattle he always found bacteria. BQco ( 5 ) fancies that the normal lungs often contain bacteria, as he finds bacteria, even when I' leur pCn4tration agonique peut &re exclue avcc certitude ' I ; but, even if such a statement could be accepted, the possibility of a post-mortem invasion cannot be excluded, and even BCco states that the healthy lungs of animals are generally sterile. The great majority of observers, on the other hand, are probably correct in maintaining that the lower air passages are normally sterile. In support of this view are the following facts :-(u) Although the air does not contain many bacteria, they are probably all withdrawn from the inspired air while it is passing through the upper air passages, the removal being mainly effected by the nasal mucous membrane and the adenoid tissue of the pharynx. Such is the opinion held by Hildebrandt ( 6), Buttersack (i), Muller (S), Barlow (p), and Part of a thesis for the Degree of JLD., Edinburgh University, 1899. 1 d L . OP PATII.-VOL. V11