CHRONIC INTERSTITIAL PNEUMONIA. ' 203 



separate. In other cases, the putrid contents of the dilated tubes 

 cause inflammation or diffuse putrescence of the lung. In the very 

 rarest instances, the bronchus leading to a cavity becomes obliterated, 

 when its contents may be transformed into a cheesy or calcined 



SYMPTOMS AND COURSE. In its first stage interstitial pneumonia 

 can hardly be recognized with certainty. Should the resolution of a 

 croupous pneumonia be very tardy; if we find, after the lapse of weeks, 

 that the percussion-sound continues dull and the respiration bronchial 

 or indistinct, we may anticipate that the disease will terminate in indu- 

 ration, particularly if the patient have no fever, and gradually recover 

 his health, so that we may exclude the idea of cheesy infiltration. We 

 cannot diagnose the disease with certainty until the thorax commences 

 to sink in at the affected side, and the signs of bronchiectasis appear. 



It is quite the same with regard to the interstitial pneumonia 

 which accompanies tuberculosis, and caseous infiltration of the lung. 

 As this is one of the constant complications of the above diseases, we 

 may reasonably infer that the dulness at the apex of the lung observed 

 in consumption is due in part to interstitial pneumonia. The depres- 

 sion of the supra and infra clavicular regions, which sometimes accom- 

 panies pulmonary consumption, can only be ascribed to this interstitial 

 pneumonic induration, since neither reduction of the dimensions of 

 the lung, nor depression of the thoracic wall, is produced either by 

 tubercular deposit, caseous infiltration, destruction of the pulmonary 

 'substance, or by the establishment of cavities. Although this symptom 

 (which is often erroneously called a pathognomonic sign of consumption) 

 is a very common one among consumptive patients, yet this is only 

 because the process by which the lung is destroyed is almost always 

 accompanied by a chronic pneumonia, which causes its induration and 

 contraction. When chronic pneumonia is associated with chronic 

 bronchitis and emphysema, depression of the thoracic wall is less com- 

 mon. In such cases the only diagnostic signs are the coughing-fits, 

 characteristic of the existence of cavities with rigid walls, and the na- 

 ture of the sputa. 



When the disease is somewhat extensive, signs of dilatation and 

 hypertrophy of the right side of the heart are added to the symptoms 

 above described ; and at a later period, where hypertrophy of the heart 

 is no longer capable of counteracting the effects of obstructed circula- 

 tion, cyanosis appears, with blueness of the lips, puffiness of the face, 

 enlargement of the liver, and finally dropsy, symptoms which, as we 

 have learned, also accompany emphysema. An explanation of this is 

 easy ; the obstacle to evacuation of the right heart manifestly pro- 

 ceeding from atrophy of the pulmonary capillaries. We rarely observe 



