Macklin and Macklin 361 



of a previous attack of any pneumonopathy engendered by PIE, such as pneu- 

 mothorax. It is likely, too, that at least some of the pulmonic diseases favoring 

 PIE can be sidestepped, or their dangers lessened, by proper health measures. 

 The prompt removal of foreign bodies and exudate plugs from the bronchial 

 tree, where possible, is particularly enjoined. But, after all this has been said 

 and done, many cases will still occur. What then? 



It is most important that the physician should become airblock "conscious." 

 Since such signs and symptoms as dyspnea and cyanosis are so frequently as- 

 sociated with primary cardiac incompetence, it is but natural for the physician 

 who finds them present to make his diagnosis "heart disease" of some kind, and 

 let it go at that. When he does this, all opportunity to relieve an existing air- 

 block by depneumatization goes by the board. The physician should always 

 think of the possibility of airblock whenever his patients have such things as 

 dyspnea, cyanosis, inspiratory thoracic fixation, subcutaneous emphysema, 

 tympanites, pneumothorax, anginoid pains, or the peculiar "crunching" sound 

 in the precordium— or, indeed, whenever any predisposing condition is present, 

 particularly atelectasis. An X-ray examination, especially by the lateral pro- 

 jection, should be done as soon as possible to reveal air-pockets,— above all, 

 those of the substernal region. PIE and mediastinal emphysema may be pres- 

 ent, however, when no air has yet reached the anterior mediastinum. 



Air is most conveniently attacked when it is trapped in the anterior medi- 

 astinum. The technic, by aspiration through a hollow needle, has been made 

 clear by Gumbiner and Cutler,^ and has been particularly successful in the 

 very young infant. For air in the posterior mediastinum the method which 

 Tiegel employed, of suction applied to an incision in the root of the neck, may 

 be used.- Withdrawal of air from this site by way of a catheter insinuated into 

 the mediastinum might also be done when indicated. 



Summary 



A knowledge of the functional anatomy of the lung and connected parts, 

 gained by the experimental method, has enabled us to understand many salient 

 features of pulmonic interstitial emphysema and its sequelae occurring in the 

 course of disease and adverse physical conditions. We have found that the 

 anatomical weak spots of the air-container system are the "non-partitional" 

 alveolar bases which lie upon connective tissue. Particularly important as po- 

 tential air-leakage points are those bases which enclose the terminals of the 

 pulmonary arteries and veins. Under adverse conditions these bases are over- 

 strained and are ruptured when the alveolar air pressure rises beyond their 

 powers of resistance. The leak-promoting overstretching of the perivascular 

 bases is seen as an exaggeration of a normal change in them during inspiration, 

 in the course of which the caliber of these vessels is increased to facilitate blood 

 flow through the lungs. We feel that this conception of the usefulness of in- 

 spiratory stroma-pull has not been sufficiently appreciated by physiologists 

 whose attention seems to have been focused on the capillaries rather than the 



