BEONCHIECTASIS. 309 



secretions are more likely to stagnate in them. The direction of 

 the larger bronchial branches of both upper lobes and of the 

 right middle lobe is outwards, upwards, and forwards, whilst 

 those of the lower lobes of both lungs pass downwards, inwards, 

 and backwards. Consequently it is usual to find bronchiectasis 

 limited to the lower and middle portions of the lungs, whilst the 

 upper lobes, and particularly the territory of the vertical apical 

 bronchi, escape. The greater length and narrowness of the 

 bronchi of the left lower lobe may account for the greater 

 frequency of bronchiectasis of the left side. 



Since the connective tissue sheaths of the bronchi are 

 continuous with the lobular septa of the lungs, and these septa 

 in turn fuse with the visceral pleural envelope, it is evident that 

 obliteration of the pleural cavity by adhesions will permit the 

 inspiratory movements of the chest to make centrifugal traction 

 on the bronchi. If these tubes are weakened by inflammation 

 the traction may induce dilatation. It appears, however, that 

 pleural adhesions are not at all common in the early stages of 

 bronchiectasis, many cases of which originate in childhood as 

 sequels to the lung inflammations of measles and of whooping 

 cough. 



Dilatation of bronchi is, in some instances, due to pressure on 

 the roots of the lungs. The left bronchus being in intimate 

 relation with the oesophagus, the aorta, and the bronchial glands, 

 pressure on this tube is usually due to aneurysm, malignant 

 disease of the oesophagus, or glandular swellings. The right 

 bronchus is in relation with the back of the ascending aorta and 

 the bronchial glands, so it is liable to pressure from an aneurysm 

 or from glandular enlargements. Extreme dilatation of the left 

 auricle in mitral stenosis has been known to cause compression 

 of the left bronchus. 



A foreign body lodged in a bronchus is sometimes the cause of 

 bronchiectasis. There is some difference of opinion as to whether 

 foreign bodies are more frequent in the right or the left bronchus. 

 The right bronchus is the larger, and it would be expected that a 

 small body would either fall directly into it, or, on account of the 



