1874.] the Lymphatic System of the Lungs. 137 



a constant growth and reproduction of these follicles is going on. The 

 lymphatic vessels of the two last-mentioned systems anastomose with 

 each other in the ligaments of the lung, and finally enter the bronchial 

 lymphatic glands. 



B. Pathological conditions. 



I have already mentioned the germination of the endothelium of 

 the surface, and the hypertrophy of the muscles, in chronic diseases of 

 the lung. 



In many chronic inflammatory processes of the lung (chronic pyaemia, 

 artificial tuberculosis, chronic pneumonia) the pleura pulmonum becomes 

 the seat of nodules of various sizes and shapes. Generally they are more 

 or less round, and correspond in position to those superficial portions of 

 the lung which have become the seat of an inflammatory process. These 

 nodules of the pleura are due to a very rapid proliferation of the branched 

 connective-tissue corpuscles, simultaneously with an increase of fibrous 

 connective tissue, this latter fact being very obvious when the nodules 

 have reached a certain age. As long as they are small, they show merely 

 an abundance of cellular elements ; in their later stages they become 

 richly supplied with capillary blood-vessels. 



Lungs of guineapigs that are far advanced in the process of artificial 

 tuberculosis (t. e. where the bronchial glands have already become the 

 seat of cheesy deposits) show superficial nodules, which are in direct con- 

 tinuity with the subpleural lymphatics. In horizontal sections through 

 such portions of the lung, one finds these lymphatics filled with lymph- 

 corpuscles, while at a later period they are occupied by an adenoid reti- 

 culum, the meshes of which contain lymph-corpuscles, and which is in 

 direct continuity with the endothelium of the lymphatic tubes. The no- 

 dules themselves represent a network of cords, which very much resembles 

 adenoid tissue. The meshes of this network of trabeculae are the alveoli, 

 which, at an early period, contain a few lymphoid corpuscles, while the 

 epithelium is, at the same time, in a state of germination, the individual 

 cells being swollen and the nucleus in a state of division. At a later period 

 the alveoli are filled with small lymphoid corpuscles, while the epithelium 

 of the alveoli is no longer to be distinguished as such. The blood-capil- 

 laries belonging to these alveoli have undergone some remarkable changes, 

 of which I shall speak at length afterwards ; at present I will only 

 mention that at a later period they are no longer permeable for the blood. 

 These interalveolar trabeculse of adenoid tissue, forming the framework 

 of the superficial nodules, are developed from the branched connective- 

 tissue corpuscles of the alveolar septa. The same process extends to the 

 subpleural lymphatics, originating from these interalveolar connective- 

 tissue corpuscles, in such a way that these lymphatics- become con- 

 verted into cords of adenoid tissue connected with their endothelium. 

 Consequently these lymphatics become converted into endolymphangial 

 cords. 



