136 Dr. E. Klein on the Anatomy of [Jan. 29, 



membranes. As these branched cells have a corresponding lymphcanali- 

 cular system, it is easy to understand why Sikorski, in his experiments, 

 found that carmine entered freely from the cavities of the alveoli into the 

 interalveolar lymphatics. But there is no other communication between 

 the cavities of the alveoli and the lymphatics than by means of these 

 pseudostomata. It can be easily understood that the pseudostomatous 

 canals (viz. the canal in which lies the process of a cell projecting freely 

 into the cavity of an alveolus, and the lymphcanalicular system, in which 

 the interalveolar branched cells lie) may become occasionally distended, e. g. 

 in inflammation, by exudation, or by migratory cells. In fact, it must be 

 assumed that cells, such as are produced by catarrhal inflammation of 

 the air-passages, migrate from the cavities of the alveoli into the in- 

 teralveolar lymphcanalicular system through those pseudostomata ; and 

 the same assumption must be made for the well-known large granular 

 mucous corpuscles, in many lungs, containing carbon particles, inasmuch 

 as similar cells are found in the interalveolar tissue. 



3. Peribronchial lymphatics. The third system of lymphatics is com- 

 posed of lymphatic vessels which are chiefly distributed in the adventitia 

 of the bronchi. I shall therefore call it the system of peribronchial 

 lymphatics. The vessels of this system are usually distributed around the 

 bronchi, anastomosing with each other, and especially with the perivascular 

 lymphatics. The vessels of the peribronchial system take up capillaries, 

 which originate in the mucous membrane of the bronchi and penetrate 

 through the tunica muscularis of the bronchi. These capillary branches 

 originate in the usual way ; i. e. their wall is continuous with the branched 

 cells of the mucosa, which cells in turn penetrate, as a nucleated reticulum, 

 between the epithelial cells of the bronchus, and project on its free surface. 

 From this it may be understood how particles can penetrate from the 

 cavity of a bronchus into the peribronchial lymphatics, as in the experi- 

 ments of Sikorski. The lymphatics are always most numerous on that 

 side of a bronchus which is directed towards a branch of the pulmonary 

 artery. In the course of each bronchus, especially those that possess only 

 a thin muscular tunic and no trace of cartilage, there are generally several 

 vasculated lymph-follicles to be met with, which are placed in continuity 

 with the endothelial wall of a lymphatic vessel, in such a manner that 

 they are surrounded by that lymphatic vessel, in the same way as the 

 lymph-follicles of Peyer's patches are by their lymph-sinuses. These 

 follicles, already seen by Dr. Burdon Sanderson, extend up to the tunica 

 muscularis ; in some instances they are to be traced through this latter into 

 the mucosa. They always lie in the wall of a lymphatic vessel, between the 

 bronchus and the accompanying branch of the pulmonary artery. They 

 are of different sizes, and are generally spherical or elliptical ; sometimes 

 they represent merely a cord-like thickening of the wall of the lymphatic 

 vessel. In the lung of the guineapig these perilymphangial follicles are 

 very numerous ; they are not so numerous in rabbits. It can be proved that 



