HO DISEASES OF THE PARENCHYMA OF THE LUNG. 



important aid to expiration, elasticity of the lung. The cyanotic symp- 

 toms occur because the right heart, having fewer efferent channels, 

 owing to obliteration of so many pulmonary capillaries, is imperfectly 

 emptied, thus causing venous engorgement of the aortic circulation. 

 According to this explanaticai, the more unequally atrophy of other 

 organs and general reduction of the volume of the blood keep step with 

 the atrophy of the lungs, so much the more marked must the symptoms, 

 above described, become. 



As the thin, emaciated, thoracic walls and their flexible ribs are 

 easily thrown into vibration, the percussion-sound is remarkably loud 

 and full. The dulness over the heart and liver is increased. Upon 

 auscultation, the greater the difference is between the capacity of the 

 contracted bronchioles and that of the air-vesicles in which they termi- 

 nate, so much the harsher is the vesicular murmur. 



Treatment of senile atrophy of the lung is out of the question. 



CHAPTER III. 



EMPHYSEMA OF THE LUNG. 



BY emphysema of the lung is meant either a morbid enlargement 

 of the pulmonary vesicles, arising mainly from the blending of several 

 vesicles so as to form one great cyst emphysema vesiculare or else 

 die escape of air into the subpleural and interstitial connective tissue 

 emphysema interlobulare. The latter is analogous to emphysema of 

 other organs, such as the subcutaneous areolar tissue ; the former, like 

 oedema of the lungs, has no analogue elsewhere. 



ETIOLOGY. The opinions of authorities as to the mode of origin of 

 vesicular emphysema of the lungs differ materially. Four principal 

 theories have been advanced upon the subject. According to the first, 

 emphysema arises through immoderate or too protracted inflation of 

 the air-cells, by forced and long-continued inspiration theory of inspi- 

 ration. According to the second, likewise, emphysema is the result of 

 excessive mechanical distention of the vesicular walls, but is not pro- 

 duced by inspiration, but by forced expiration theory of expiration. 

 According to the third, its origin is not mechanical, but it arises from 

 nutritive derangement of the lung-substance, which occurs indepen- 

 dently of any strain or stretching. Finally, according to a fourth view, 

 advanced by Freund, a morbid condition, namely a rigid enlargement 

 of the thorax, constitutes the primary disease, to which dilatation of the 

 air-cells is only secondary. "We believe each view to be true in certain 

 cases, but no single one will account for all forms of the disease, and 

 consequently adhere to the classification into vicarious and substan- 

 tive emphysema. 



