On auscultation, a marked feature of the disease is the difference between in spiration and expiration. While the former is feeble, sufficiently so some times as to be hardly audible, and short ened, the expiration is greatly prolonged, low in pitch, wheezy, and comparatively coarse, while, if bronchitis be a feature of the case, there are moist riles and other symptoms peculiar to this compli cation.
Percussion yields a peculiar drum-like note, the "band-box" tone of Biermer, especially marked over the emphysema tous area. This sometimes so overlaps the cardiac area as to cause disappearance of the cardiac dullness, and sufficiently extend downward on the right side as to bring the upper margin of the hepatic dullness to a much lower level. Occa sionally the splenic dullness is influ enced in the same manner. Occasionally a net-work of dilated veins outlines the junction of the diaphragm to the an terior wall. Palpation enables the ex aminer to realize the diminished chest expansion and the almost complete disappearance of the respiratory frem itus.
Prognosis.—The prognosis of emphy sema is, as a rule, unfdvorable when the disease is at all advanced. The local lesions progress steadily, though very slowly, and the patient is often carried to his grave by intercurrent disorders, especially pneumonia. A heart disorder is almost always present as a direct result of the interference with the circulation, and dropsy and death may ensue from cardiac hypertrophy and distension. The disease is one of long duration; its progress may be stayed to a great extent by removal to a warm and equable cli mate, by proper hygienic surroundings, and general comfort.
Etiology. — Bronchitis, asthma, and, more rarely, pertussis are the main causes of pulmonary emphysema; to these factors may be added excessive and prolonged manual labor, playing on wind-instruments, glass-blowing, and other conditions inducing undue air pressure within the pulmonary lobules. All these etiological factors bring on emphysema, however, only when the lung-tissue is congenitally weak. The nutritive changes in the air-cells play an important role in the production of the affection: a fact strongly sustained by "the markedly hereditary character of the disease and the frequency with which it starts early in life." Osler lays special stress upon these two points, and refers to the observations of James Jackson, who, out of twenty-eight eases, studied under Louis's direction, found that in eighteen one or both parents were af fected. It is also- observed in several
members of one family. Asthma brings on emphysema by interfering with the exit of air. It may also be brought on by mitral disease as a result of the pul monary congestion induced.
Two essential factors contributing to the enlargement of the chest in hyper trophic emphysema are defective pul monary elasticity and dyspnwa. Mere loss of pulmonary elasticity, by induc ing thoracic expansion, is sufficient to bring about emphysema. Diminution of the exniratnry range is one of the worst aspects of emphysema, and is . brought about by fixation of the chest. The treatment should aim at preserva tion of the elasticity of the lungs, pre vention of the overaction of the costal elevators, so as to check thoracic expan sion, and maintenance of the normal mobility of the thorax. H. Campbell (West London Med. Jour., p. 177, July, '97).
Complete occlusion of the nares pro duces emphysema in a few days and changes the respiratory rhythm, the fre quency of respiration being decreased and the depth of respirations being increased. A smaller quantity of air enters the lungs when the animals breathe only through the mouth than when the nose is used in respiration; hence it is fair to conclude that when nares were occluded the dogs were forced to take deeper inspirations in order to compensate for the diminished volume of air entering the lungs; pul monary emphysema, therefore, depended in them upon the increased volume of respired air: a purely mechanical result of occlusion of the nares. Bullara forma Medica, NOS. 18:3 and 18-I, 1900).
Pathology.—When the lungs are ex amined post-mortem, they are found to be greatly enlarged and devoid of ticity. When cut, they are pale and occasionally show an absence of pigmen tation: Virchow's "albinian condition." Specimens of emphysematous lungs exhibited to the Berlin Medical So ciety, showing absence of pigmentation, termed by the author an albinian con dition of the lung, sometimes found in post-mortems. Tubercles never found in a lung which was the seat of emphy sema, and in only one instance pneumo thorax found. Virchow (Berl. lclin. Woch., Jan. 2, 'SS).