Morbid Anatomy.—Pulmonary emphysema may be of the interlobular or vesicular variety.
In interlobular emphysema the air occupies the connective tissue lying between the lobules and under the pleura. When infiltrated into the tissue between the lobules, air collects in small bubbles like little beads. \VI:len in the sub-pleural tissue, it forms blebs of varying size—sometimes isolated, when they may reach the size of a small nut ; sometimes arranged in lines, when they are rarely larger than an ear of wheat. Their shape is elongated or sphericaL When thus extravasated into the pulmonary con nective tissue, the air has been known to make its way into the anterior or posterior mediastinum and thence into the sub-cutaneous tissue of the face and neck. Thus, in a case published in 1834 by Dr. Bird Herapath a child eighteen months old who had died of bronchitis secondary to whooping-cough—air was found to have escaped from one of the lobules seated at the root of the right lung into the anterior mediastinum. Start ing from this point the air, without entering the pleura, had escaped along the sub-pleural connective tissue and formed numerous emphysematous swellings on the lung. It had distended the areolar tissue of the anterior mediastinum, and passing upwards had infiltrated into the cellular tissue of the neck, beneath the deeper cervical fascia and the subcutaneous tissue of the neck and chest. A similar case, in a child four months old, has been recorded by Dr. Pepper, of Philadelphia. In rare cases pneunao thorax has been produced by rupture of the pleura and escape of air into the pleural cavity.
Interlobular emphysema is almost always produced by rupture of an air-vesicle during a violent fit of coughing. It may, however, be the result of injury from without.
In vesicular emphysema the apices and anterior borders of the lungs are the parts commonly affected. These portions are dull white in colour, dry, and bloodless. They convey to the finger a peculiar soft sensation, which Hervieux has compared to that noticed when pressing a piece of wadding covered with satin. Close inspection in a good light shows a multitude of little, bright, transparent points the size of a pin's head.
Sometimes rather larger projections are visible, and these are often angular.
When the chest is opened in these cases the hmgs remain distended, and their anterior borders are usually in contact so as to hide the greater por tion of the cardiac surface.
Symptoms.—Interlobular emphysema, unless the air spread through the mediastinum to the sub-cutaneous tissue of the neck and chest, gives rise to no symptoms. Its existence is only discovered on post-mortem examina tion of the body.
Even in the vesicular variety the limited amount of emphysema which is found when the disease is acute, as in cases of catarrhal pneumonia, or acute bronchitis with collapse, gives little evidence of its presence. Our knowledge of the morbid anatomy of such cases enables us to infer its ex istence, but the occurrence of abnormal dilatation of the air-cells given rise to no additional symptoms, and produces no characteristic modification of the physical signs.
It is in the chronic form of the disease that we are able positively to determine the existence of over-distention of the pulmonary alveoli. In a pronounced case of emphysema the symptoms and physical signs are those familiar to us as a consequence of a similar condition in the adult. Such children, as has been already remarked, almost always present the char acteristic features of the strumous constitution. The patient is usually short for his age and of sturdy build. His head is rather large, his neck short with prominent jugular veins, and his face pallid with a blueish tint round the mouth and eyes. The chest is flattened laterally at the base, and the lower part of the sternum is somewhat projecting. Consequently, its antero-posterior diameter is increased. The intercostal spaces are obliterated, and in rare cases slight bulging may be noticed above the clavicles. Sometimes the back is a little rounded, but I have never noticed the stoop of the shoulders, which is such a marked feature in the adult, unless the emphysema were combined with a persistent chronic bronchitis. The heart is pushed down so as to be felt beating in the epigastrium, and the liver and spleen are often appreciably displaced.