318 CLINICAL APPLIED ANATOMY. 



fixed by adhesions. When lung contracts, compensatory em- 

 physema or local retraction of the chest wall may be expected. 

 The close adhesion of the visceral pleura to the lung, and its 

 permeation by some of the pulmonary lymphatics, are sufficient 

 to account for the frequency of pleurisy and of pleural adhesions 

 in phthisis. Small groups of recent tubercles may often be found 

 in the visceral pleura of those suffering from the disease. 



PNEUMONOKONIOSIS. 



In this group of diseases the inhaled dust forms a natural 

 injection of the lymphatics of the lungs. The bulk of experi- 

 mental evidence shows that no absorption of particles takes place 

 through the mucous membranes of the trachea and bronchi, 

 where the presence of an impermeable basement membrane cuts 

 off the lymphatics of mucosa from those of the deeper structures. 

 After the prolonged experimental inhalation of air loaded with 

 fine particles, the latter are found in the peribronchial and peri- 

 vascular lymphatics, in the lymphoid tissue in connection with 

 these and in the bronchial glands, positions to which they are 

 carried after they have been absorbed by the alveolar lymphatics. 

 In pneumonokoniosis the foreign particles lie in the desquamated 

 epithelium and epithelial spaces of the alveoli, in the iriterlobular 

 septa and the lymphatics which surround the pulmonary arteries 

 and bronchi, in the deeper layers of the visceral pleura, in the 

 lymphoid aggregations of the lungs and in the bronchial glands. 

 There is practically no deposit in the superficial layers of the 

 visceral pleura, for the pulmonary lymphatics do not run in 

 these layers, and there is no deposit in the mucous membrane 

 of the bronchi, since the ciliated epithelium passes the particles 

 upwards and no direct absorption takes place into the deeper 

 layers owing to the presence of the basement membrane. 



EMPHYSEMA. 



Interstitial emphysema is due to the rupture of an air cell 

 into the supporting fibrous tissue of the lung. It is practically 



