114 DISEASES OF THE PARENCHYMA OF THE L.UNG. 



one ; according to which, wasting, perforation, and final disappearance of 

 the vesicular septa are not always due to a mechanical process, but may 

 proceed from nutritive disturbance, and from other causes at present un- 

 known to us. Perhaps most cases of inherited emphysema belong to 

 this class. 



The occurrence of rigid dilatation of the thorax as a primary dis- 

 ease, causing permanent inspiratory expansion, strain, gradual atrophy 

 of the cell-walls, and consequent emphysema, according to the theory 

 of Freund, is certainly rare and exceptional. As we shall show by- 

 and-by, in a large majority of instances, rigid dilatation of the chest 

 and the nutritive disorder characteristic of emphysema occur together, 

 and arise from the same causes. I cannot, however, deny having met 

 with a few cases which seemed to support the theory of Freund cases 

 in which a marked rigid dilatation of the chest had occurred during the 

 period of puberty, without any sign of emphysema, but in which ex- 

 treme emphysema had developed a few years later. 



Interstitial emphysema arises from an over-distention and rupture 

 of the air-vesicles adjacent to the pleura and interlobular interstices, 

 with escape of the air into the sub-pleural and interstitial connective 

 tissue. This excessive distention takes place sometimes from very vio- 

 lent coughing, like that of whooping-cough, sometimes in cases where 

 a large number of air-cells are prevented from taking part in occupation 

 of the space created by inflation of the chest The frequent, though 

 somewhat inexplicable, appearance of interstitial emphysema after croup 

 is, perhaps, most probably attributable to the bronchitis, which, according 

 to Bolm and Gerhardt, constantly complicates laryngeal croup, and 

 often causes partial collapse of the lung. 



Predisposition toward emphysema is sometimes congenital. It often 

 appears during childhood as a result of whooping-cough (which is almost 

 exclusively a disease of that age), as well as in consequence of the fre- 

 quent and tedious bronchial catarrhs to which scrofulous and rachitic 

 children are so liable. The period of advanced middle life, however, 

 furnishes the main portion of emphysematous patients, when the " ca- 

 tarrh sec " is most prevalent. 



From the above it appears that the exciting causes of the malad} 

 are chronic inflammation and wasting of the lung, inflammation of the 

 pleura, with extensive adhesions, chronic catarrh of the lesser bronchi, 

 with contraction of then- calibre; frequently-recurring coughing-fits, 

 especially those of whooping-cough and of dry bronchial catarrh ; the 

 playing upon wind-instruments, and similar procedures ; lifting heavy 

 burdens, and severe corporeal exertions. In some cases the exciting 

 causes are unknown. 



ANATOMICAL APPEAKANCES, The almost universal statement, that, 



