364 Pulmonic Interstitial Emphysema 



involving the bronchi, such as bronchopneumonia, where the bronchi are 

 plugged by exudate or by swelling of the walls. Certain allergic conditions be- 

 long here. Spasmodic contraction of the bronchial musculature predisposes. 

 The important thing is that compensatory emphysema is thus set up. In- 

 flammatory changes involving the stretched nonpartitional bases may still 

 further weaken them and make them more easily ruptured; and additional 

 impetus in this direction is provided by acts which raise the intra-alveolar 

 pressure, as coughing. Influenza has been found to be very important in in- 

 ducing PIE. Whooping cotigh is serious. Such cases of PIE are regarded as 

 being due primarily to overstretching of the nonpartitional bases, often 

 having deteriorated protoplasm, combined with intermittent elevation of 

 intra-alveolar pressure. 



An effect similar to atelectasis is produced by diminution of lung volume 

 from the ablation of a lobe or an entire lung, for the remaining part, withotU 

 thoracoplasty, has to become overexpanded. There is here, however, a com- 

 pensatory feature in the increased blood volume in the surviving parts, which 

 acts thus oppositely to what we have termed "Factor 'B,' " and which would 

 in this way tend to offset the action of Factor "A." Occlusion of the bronchi 

 from without may also induce collapse, but this, being gradual in onset in 

 most cases, is not regarded as so provocative of air leakage from the associated 

 compensatory alveolar ectasia as is the case when the onset is sudden. In this 

 class we have pressure from new growths, particularly primary cancer, or from 

 scars, as in tuberculosis, silicosis, etc. Reduction of volume, too, may occur 

 from continuous presstue on the chest wall, as in lying on the side for a long 

 time, with sudden release, setting up an overstrain in presumably over- 

 distended areas of the lung. There are some cases which support this assump- 

 tion. The noninflation cases occurring soon after birth make a special class, 

 where leakage has taken place on account of the relative overexpansion of 

 aerated parts of the lung. This grotip is notable for the brilliant progress 

 already made in diagnosis and treatment. In some cases, considered tmder the 

 heading "miscellaneous," it is difficult to do more than speculate as to exactly 

 how the PIE is brought about; but here, as in all others, the nonpartitional 

 bases must be involved, and the fundamental features of etiology are doubtless 

 the same as elsewhere. 



There are other types of case showing PIE and its effects in which the 

 primary factor in bringing about the multiple rupture of the nonpartitional 

 bases seems to be a raised intra-alveolar pressure, though there is nothing to 

 rule oiu coincidental overstretching of these bases, at least in some areas. 

 Prominent in this class, at the moment, is lung blast, during the compression 

 phase; and we have given consideration to this condition and made suggestions 

 for its relief. Here there is sudden violent pressure on the chest. Crush injuries 

 of the chest by impaction of solid masses are somewhat analogous. An interest- 

 ing type of PIE formation occurs in apparently healthy individuals in which 

 the only obvious cause is increased intra-alveolar pressure from violent expira- 



