502 THE RESPIRATORY SYSTEM. 



taken up by the epithelium of the air spaces, in part are carried by pha- 

 gocytes or otherwise to the interstitial tissues of the lungs (Fig. 283). 

 Here, either within cells or without, they are deposited along and withiii 

 the lymph -channels or in the lymph -nodules of the pleura and interstitial 

 tissue, or they may be carried to the lymph-nodes at the root of the 

 lungs. Barely, this inhaled dust passes the tracheal and bronchial 

 lymph-nodes and may be deposited in the viscera, especially in the liver 

 and spleen. 



Under ordinary conditions a considerable deposit of inhaled pigment 

 particles in the lungs does not seem to be of great significance, though 

 there is little doubt that it may predispose to more serious lesions. On 

 the other hand, miners and others working or confined in smoky air, 

 stone or metal workers, and the like are liable to excessive pigmentation 

 and develop interstitial pneumonia, especially marked at first along the 

 iuterlobular septa and frequently associated with chronic bronchitis, 

 emphysema, atelectasis, or bronchiectasia. This condition of the lung 

 when due to the inhalation of coal dust is called anthracosis ; when due to 

 dust of various minerals, chalicosis ; when due to iron dust, siderosis. 1 

 The general process has been called pneumokoniosis. The color varies in 

 these lungs with the character and amount of the deposited material, 

 which is frequently quite unevenly distributed. The amount of foreign 

 material in such lungs is sometimes large. 2 



TUBERCULOUS PNEUMONIA. 



General Considerations. Tuberculous inflammation of the lungs is sim- 

 ilar in nature to tuberculous inflammation in other parts of the body. 

 But since the character of the response of a tissue to injury is largely 

 dependent upon the form and capacities of its cells, it is not surprising 

 that in such complex organs as the lungs, the lesions of tuberculosis 

 should present many variations from the usual type elsewhere. The 

 bronchial passages and the connecting air spaces, the numerous blood- 

 and lymph-channels especially favor the distribution of the tubercle 

 bacillus within these organs ; the open texture of the lungs permits, as in 

 other forms of pneumonia, of great accumulation of exudate, while the 

 delicacy and thinness of the air chambers favor extensive disintegration 

 of the old or new-formed tissues or exudates when these have become 

 necrotic under the influence of the poisons of the tubercle bacilli. 3 



Thus the variety of cells and tissues involved and their peculiar rela- 

 tionships to one another and to the invading organisms render the lesions 

 of pulmonary tuberculosis more complex in morphology than are tuber- 

 culous lesions in any other part of the body. 



The classification of these lesions is largely based upon topographic 



1 For a study of the condition of iron pigment in cells and tissues see Arnold, 

 Virch. Arch., Bd. clxi., p. 284, 1900. 



4 For an analysis of the lungs of a case of extreme anthracosis see Ilodenpyl, Trans 

 New York Path. Soc., 1899-1900. 



3 For further details concerning the lungs in inflammation see p. 4b8. 



