Diagnosis.—The diagnosis presents no difficulty except in the determination of the primary or secondary origin of the trouble. The chief difficulty occurs in children, where time alone may be able to decide the question as to whether the bronchitis is "simple" or is the premoni tory stage of pertussis or measles.
,Etiology.—The causes may be classi fied as mechanical, chemical, infectious, and toxic. Of mechanical causes are the inhalation of dust, particles of food, etc.; of the chemical as the inhalation of irri tating gases (such as chlorine); of in fective, that occurring in the course of measles is the most marked. Among the toxic causes the poison of urmia and possibly that of some of the infections must be included, the latter upon the theory that the inflammation is produced by the excretion of toxins by the respira tory tract.
Exposure to cold and damp is an etio logical factor probably acting by lower ing bodily resistance and allowing the invasion of the mucous membrane by micro-organisms constantly present, but under ordinary circumstances impotent. The possibility of bronchitis being produced by the elimination through the respiratory passages of materials or dinarily passed out through the other emunctories cannot be certainly cast aside. Bronchitis has also been ascribed to the effects of ether, employed as an anmsthetic.
The infective nature of acute bron chitis has not hitherto been generally accepted. In health the great majority of observers find the lower air-passages sterile, the bacteria being withdrawn into the upper air-passages, chiefly by the nasal mucous membrane and the adenoid tissue of the pharynx. Jundell, for ex ample, examining the tracheas by means of a special instrument, in forty-three people found it either quite sterile or else containing only scanty transitory bacteria.
Personal cases grouped in two sec tions:— Cases of bronchitis without pneumonia 27 Cases of bronchitis with pneu monia 22 In all but 6 pathogenetic bacteria were found in great numbers.
Of these, those most frequently pres ent were streptococcus pyogenes—found in 2 cases in pure culture, in 19 in association with other pathogenetic bac teria; diplococcus pneumonim—found in 15 cases of pure bronchitis and in S of bronchitis with pneumonia, and in these 23 cases in large numbers in all but 2, never in healthy bronchi ; in fluenza bacillus—found in 17 out of 49, never alone.
Acute bronchitis is an infective dis ease, not due, however, to any specific organism; it is usually a mixed infec tion, the most important agents being the streptococcus pyogenes and the diplococcus pneumonia. The influenza bacillus not infrequently produces bron chitis apart from influenza. Ritchie (Jour. of Path. and Bact.; Practitioner, May, 1901).
Bronchitis is frequently caused by the extension of diphtheria and erysipelas from the upper tract, but in that case cannot be considered as simple bron chitis.
mucous membrane is injected, of a bright-red color, is ened, and thrown into longitudinal folds. The surface is usually covered with more or less mucus or muco-pus. On section there is found leucocytic infiltration of the deeper layers. The epithelial layer shows active proliferation of the cells; goblet-cells are numerous and greatly distended; the cells of the mucous glands are swelled and granular; and the ated epithelial cells are seen to be shed in large numbers.
The streptococcus bacillus predomi nated in all cases of bronchitis in influ enza. In quite a number, and some of the worst, it was the only bacterium found in the expectoration. In 23 cases the streptococcus was associated with staphylococci alone; in 3 cases strepto cocci, staphylococci, and the influenza bacillus were associated; in 27 cases the streptococcus alone was found. The in fluenza bacillus disappeared after a short time, and was replaced by the streptococcus. F. Forchheimer (Med. News, June 1, 1901).
Many instances observed of localized bronchitis in which the sputum is crowded with diplococcus pneumonim. This suggests that these micro-organ isms are the essential causal factor in a large proportion of such cases. This germ tends to affect localized areas in one or more pulmonary lobes and usually runs a benign course. There is also a tendency of recurrent attacks to implicate the same area again and again. P. W. Williams (Bristol Med. Chir. Jour., June, 1902).