EMPHYSEMA OF THE LUNG. 



npon opening the chest, the emphysematous lungs bulge forcibly out 

 of it, is incorrect, or at least inexact. This active projection of the 

 lungs from the thorax, when opened, is not the effect of emphysema 

 alone, and is only met with in cases where, besides the emphysema, 

 there is a wide-spread obstruction of the smaller bronchi, whereby the 

 escape of air from the chest is prevented, while, during the last breath 

 of the dying patient, the respiratory muscles relax, and the thorax col- 

 lapses. True, emphysema is very frequently complicated with capillary 

 bronchitis, which is the chief cause of obstruction of the minuter bronchi 

 and of the retention of air in the vesicles ; and, we may add, that em- 

 physema, by reducing the elasticity of the vesicular walls, and thus 

 diminishing their expulsive power, favors the occurrence of permanent 

 inspiratory expansion. A very small obstruction in the bronchi of an 

 emphysematous lung suffices to hinder evacuation of the air-cells. 



Although the forcible protrusion of emphysematous lungs through 

 the opening in the chest is by no means of constant occurrence in em- 

 physema, and although it is not due to the latter disease but to one of 

 its complications, yet incomplete retraction of the lung, when the thorax 

 is opened, is constant and peculiar to this affection. Even where 

 there is no complicating contraction nor occlusion of the bronchioles 

 (which would likewise prevent retraction of the lungs), emphysematous 

 lungs, when removed from the chest, or when merely exposed, remain 

 more inflated, and larger than healthy lungs. In order thoroughly to 

 comprehend this condition, about which also very erroneous ideas have 

 been propagated, we must understand why a healthy lung, upon dissec- 

 tion of the thorax, contracts to a certain extent, and then remains with- 

 out escape of the rest of the air which is in the vesicles. When, by ex- 

 posure of the lungs, upon autopsy, we allow the atmospheric pressure 

 to act upon their exterior surface, all air would immediately escape 

 from the vesicles, and their walls would collapse like those of an empty 

 sack, were it not that their outlets open into those narrow, heavily and 

 thickly-walled tubes, the bronchi. Owing to their weight, the bronchi 

 soon collapse, and thus prevent further escape of air from the vesicles. 

 A simple experiment will demonstrate this fact: If we remove a 

 stomach and oesophagus from a body, and, after tying the pylorus, in- 

 flate them, only a portion of the air will escape from the stomach after 

 we cease blowing, because the heavy walls of the oesophagus collapse 

 and oppose its further egress. This would be still. more marked, did 

 not the elasticity of the air-cells, to some extent, counteract the resist- 

 ance set up by the weight of the bronchial wall. The vesicular walls 

 of an emphysematous lung are thinner and slighter than those of a 

 healthy lung. Besides, they have lost a considerable part of their elas- 

 ticity, so that the reason is evident why lungs thus diseased remain 



