226 DISEASES OF THE PARENCHYMA OF THE LUNO. 



tubercular groups formed in this manner present the appearance of 

 rounded or wedge-shaped conglomerations of miliary nodules, an ap- 

 pearance rarely or never found in acute miliary tuberculosis where the 

 development of tubercle does not begin in the bronchial mucous mem- 

 brane. The pneumonic process by which the tuberculosis is attended 

 hi tuberculous consumption is much less extensive, as a rule, than that 

 which accompanies the consumption which is solely due to chronic 

 pneumonia, or than the form in which secondary tuberculosis super- 

 venes, at a late period, upon the process of induration and destruction, 

 a circumstance of some importance in the diagnosis of tuberculous con- 

 sumption. It is also quite an exceptional occurrence for a large part, 

 or, perhaps, an entire lobe of a lung, to become solidified by pneumonic 

 infiltration, nor does caseous infiltration often advance to the stage of 

 induration and contraction. The cheesy infiltration almost always 

 breaks down at an early period, so as to allow cavities to form. It is 

 true that we now and then find the apex of the lung to be the seat of 

 callous induration, or of a deposit of thickened caseous matter, or a 

 bronchiectasis, but it is easy to satisfy one's self that these lesions 

 have no connection with the final disease, and that they are the results 

 of some morbid process of prior date. 



As it appears from what has been stated above, the bronchi of 

 phthisical lungs exhibit a great variety of conditions. Gelatinous and 

 caseous infiltration is preceded and accompanied by purulent catarrh 

 of the finer bronchi, with dilatation of then* cavity. Disintegration of 

 a deposit of caseous infiltration is ushered in by ulceration of the bron- 

 chial wall, and the liquefaction almost always begins in the immediate 

 vicinity of the bronchus. In tubercular consumption, the eruption of 

 miliary nodules appears upon the mucous membrane of the bronchi. 

 The majority of the cavities found in chronic consumption are of bron- 

 chiectatic origin, while, on the other side, many of the minuter tubes 

 which traverse the infiltrated and indurated lung-tissue become oblit- 

 erated. The purulent contents of a closed cavity, resulting from the 

 breaking down of caseous infiltration, are discharged by perforation 

 into a large open bronchus. We not unfrequently see several bronchi, 

 with round or oval mouths, running either squarely or obliquely into 

 such a cavity, but their entrance is always abrupt, and never gradual 

 or imperceptible. Finally, where the bronchial surface has suffered no 

 profound or structural change, it is the seat of a catarrh whose profuse 

 secretion is full of young cells. This bronchial catarrh is the main 

 source of the expectoration of phthisical persons. 



Many of the blood-vessels, especially many branches of the pulmo- 

 nary artery of the infiltrated and hardened tissue, are obliterated. In 

 the walls of cavities the obliterated vessels often form promineni 



