106 DISEASES OF THE PARENCHYMA OF THE LUNG. 



from internal haemorrhage, may be the symptoms of this exceedingly rare 

 disease, which, being absolutely deadly, is susceptible of no treatment. 



INFLAMMATION OF THE LUNGS. 



Inflammation of the lungs may properly be regarded as of three kinds : 



1. Croupom pneumonia, in which the air-cells are involved in a 

 process identical with that which attacks the mucous membrane of the 

 larynx in laryngeal croup. 



2. Catarrhal pneumonia, a process intimately related to that 

 already described as catarrhal bronchitis and laryngitis, producing an 

 augmented secretion, and active generation of young cells (pus-cor- 

 puscles), but in which no coagulable exudation is formed. In both 

 these varieties of inflammation the inflammatory products are thrown out 

 upon a free surface, the tissue of the lung itself suffering no essential 

 disturbance of nutrition. 



3. Interstitial pneumonia, which is an inflammation involving the 

 walls of the air-vesicles, and the interlobular connective tissue. As in 

 the human subject, this latter form is always a chronic disease ; it has 

 been also called chronic pneumonia, in contradistinction to the other 

 varieties, whose course is usually acute. 



CHAPTER IX. 



CROUPOUS PNEUMONIA. 



ETIOLOGY. With regard to the pathogeny of croupous pneumonia, 

 we refer to what has been said in the second chapter of the first section 

 concerning croupous inflammation, and of its distinctness from diphthe- 

 ria. In croupous pneumonia, also, a fibrinous, rapidly-coagulable exu- 

 dation is thrown out upon the free surface of the air-vesicles, involving 

 their epithelium, and including the newly-formed cells. Here, too, the 

 vesicular walls become completely restored after expulsion of the exu- 

 dation. 



Sometimes pneumonia occurs under the influence of an acute dys- 

 crasia, just as catarrh (as we have learned) attacks the air-passages in 

 measles, exanthematic typhus, etc. This form of pneumonia, which ac- 

 companies typhus more often than it does other acute infectious dis- 

 orders, may be distinguished by the name of secondary pneumonia^ 

 trom the other varieties which arise more independently, and constitute 

 a separate disease, which we may oall primary pneumonia. It is 



