212 DISEASES OF THE PARENCHYMA OF THE LUNG. 



supervening as a secondary process upon a preexisting pneumonia. It 

 is, indeed, rare for tubercles to form in a lung which does not contain 

 products of chronic inflammation. 



As the formation of tubercle never takes place unless preceded by 

 a pneumonia terminating in caseous infiltration of the pulmonary tis- 

 sue, and, as it occurs with equal frequence, whether the infiltration be 

 a sequel to croupous, catarrhal, or to chronic inflammation, we may as- 

 sume that there is no direct and immediate relationship, or community 

 of origin, between tuberculosis and the inflammatory disorders which 

 generally precede it, but that their connection is indirect, arising from 

 the caseous metamorphosis of the pneumonic product. The truth of 

 this supposition is materially supported by the fact that, in the rare 

 instances in which tubercles have developed in lungs which were in 

 other respects healthy, caseous deposits have almost always been 

 found in other organs, and no less so by the observation that, in exten- 

 sive tuberculosis, the oldest and most numerous tubercles are always 

 found in the immediate vicinity of masses of cheesy degeneration. The 

 peculiarly frequent occurrence of tubercle in the lungs is manifestly 

 because there is no other organ in which diseases arise which so often 

 terminate in caseous metamorphosis. 



Having thus distinctly stated my belief in a causative relationship 

 between caseous infiltration of the lung and pulmonary tuberculosis, 

 and having called attention to their frequent coexistence, in our next 

 chapter, we may, without impropriety, discuss the subjects of chronic 

 pneumonia with caseous infiltration, and of chronic pulmonary tubercu- 

 losis, under a common heading, as the two diseases which play the 

 principal part in pulmonary consumption. In Chapter XIV. we shall 

 speak of acute miliary tuberculosis, which is not accompanied by 

 chronic pneumonia, and which never gives rise to destruction or con- 

 sumption of the lungs. 



CHAPTER XIII. 



CASEOUS INFILTRATION AND CHRONIC TUBERCULOSIS OP THE 

 LUNGS PULMONARY CONSUMPTION. 



ETIOLOGY. [At present opinions vary widely as to the real na- 

 ture of this form of pneumonia. The terms chronic catarrhal 

 pneumonia and broncho-pneumonia do not properly characterize 

 the process ; for, on the one hand, it is not always chronic, nor, 

 on the other, is it simply a catarrh. The term " caseous pneumo- 

 nia" is open to the objection that cheesy metamorphosis is not 

 peculiar to phthisical infiltration nor to tubercle, this product being 

 also found in diseases of totally different nature ; and, moreover, 



