56 Bronchial Catarrh. 



Predisposition. Particularly predisposed to bronchial 

 catarrh are very young, or on the contrary, very old animals, 

 pet animals, anemic or cachectic animals. These may contract 

 the affection after jijainQ:|:,,^x,t^rpal causes and their recovery..j^ 

 difficult to secure. ", , ;' ,,. it 



, ^ , Pathogenesis. The mucosa of the bronchi possQ^ses pro- 

 tective features which will prevent noxious effects of external 

 influences within certain limits. Cough excited by an irritation 

 of the mucosa and the epithelial ciliary movements which are 

 directed outward favor the expulsion of particles and micro- 

 organisms out of the trachea and bronchi which have gained 

 access to the bronchial tree. The covering of the mucosa with 

 mucus protects the latter against the immediate effect of sub- 

 stances which have gained access, while the numerous Ij^nph 

 follicles that are situated in the wall of the bronchi favor the 

 destruction by phagocytosis of small elements which may have 

 penetrated into the bronchial wall itself. The very smallest 

 bronchi lack these protective structures; they are, however, 

 sufficiently guarded by the larger bronchi situated anteriorly 

 to them. The protective agencies become, however, insufficient 

 if the noxious insult has been very intense, if the protective 

 apparatus has been parah^zed, or if the detrimental stimulus 

 travels along the blood current. Whenever the harmful agencies 

 have gained the upper hand against the protective apparatus, 

 the blood vessels in the mucosa become dilated, the latter swells 

 and an increased production of mucus occurs, the substance of 

 the mucosa becomes infiltrated with a sero-cellular .exudate 

 which also collects in the lumina of the bronchi. The substances 

 acting as inflammatory irritants get in the further course into 

 the pulmonary tissue with the Mnpli current, where they again 

 excite an inflammatory process. If inflammation lasts for a 

 longer time, it leads to an increase of connective tissue and to a 

 reduction of elasticity of the bronchial wall. If the catarrh 

 is confined to the larger bronchi, the bronchial air current is 

 not influenced ; on the other hand, there is considerable disturb- 

 ance in bronchiolitis and there is the possibility of an ^xjt^fl,- 

 sion of the process to the pulmonary parenchyma. ijti.ri-n 



Anatomical Changes. In acute catarrh of the larger broiir 

 chi (macrobronchitis catarrh, ac), we find the mucosa redr 

 dened uniformly or in patches, either everywhere or only in 

 some branches, sometimes studded with small dark red extrava- 

 sated blood, more or less swollen, loosened and covered with 

 mucus or with a more purulent secretion. The size of the 

 mucous glands is from that of a millet seed to that of a hemp 

 seed and they discharge translucent drops of. Vn^ucii§^^f^|)4^ 

 pressure. , ■' ,;i'^."; . ' -Tuo 



Catarrh of the finer bronchi (bronchitis capillaris, s. bron- 

 chiolitis, s. microbronchitis catarrh, ac), can frequently, be 



