DEVELOPMENT OF THE LYMPHATICS OF THE LUNGS IN THE EMBRYO PIG. 03 



The lymphatics of the bronchi. — Miller describes two sets of lymph-vessels asso- 

 ciated with those bronchi which have cartilaginous rings and only one with those 

 which have no rings. In the former the two sets are connected by vessels that pass 

 between the rings and join the trunks situated on the outer side of these structures. 

 These trunks drain the Ij'^mphatics that accompany the smaller bronchi and empty 

 into the nodes which are situated at the hilum of the lung. While there are several 

 Ij'mphatics accompanying the larger bronchi, only three are to be found with those 

 nearer the air-sacs. These end by leaving the terminal bronchus just before it 

 ends in the atria; one of them passes to the artery, while the other two join the 

 lymphatics of the vein. 



The lymphatics of the veins. — There is a single group of vessels that extends from 

 the terminal vein to the hilac nodes. Along the larger veins there are several vessels, 

 but the terminal ones are accompanied by only one or two lymphatics. Anas- 

 tomotic vessels pass from the bronchial lymphatics to join those of the vein at each 

 branching of the bronchial tree. The lymphatics that accompany those veins 

 which go to the pleura join the pleural lymphatics. 



The lymphatics of the arteries. — The lymphatics which accompany the arteries 

 are very similar to those of the veins, with the exception that none of them pass to 

 the pleura. 



The lymphatics of the pleura. — There is only one plexus in the pleura, and this 

 drains through several large trunks to the nodes at the hilum. There are anasto- 

 moses with the lymphatics of the veins, as has been said, but the drainage probably 

 does not pass through these. Miller put his canula into a large pleural vessel and 

 injected towards the hilum. After some time the deep lymphatics, as well as those 

 of the pleura, were filled. He thought that the injection mass backed up into the 

 deep vessels from the nodes at the hilum, since both the sets of vessels drain into 

 the same nodes. 



Miller does not confirm the findings of Sappey (1874) and of Coimcilman (1900) 

 with regard to the interlobular lymphatics, l^appy thought that it was wrong to 

 divide the lung lymphatics into superficial and deep groups on account of the rich 

 anastomosis of these vessels. He thought that the lobules were surrounded by 

 lymphatics which formed networks between the adjacent l()l)ulos in much the same 

 manner as the blood capillaries do around the air-sacs. Councilman divided the 

 deep lymphatics of the lung into two sets, the bronchial and the interlobular; the 

 latter he interpreted as very important in infections. 



While Miller does not agree with these observers in regard to the interlobular 

 lymphatics, he does describe anastomoses between the lymph-vessels of the venous 

 radicles and those of the pleura, and he emphasizes the peripheral location of the 

 veins. It might well be that the vessels which Sappey and Councilman found in 

 the interlobular septa were the lymphatics of the veins, since they did not have 

 very accurate methods for the differentiation of these structures. It becomes more 

 difficult to reconcile Miller's findings with those of Flint and the results of this 

 study. Both Flint and I have found distinct groups of vessels in the interlobular 

 connective tissue in embryo pigs. These groups of vessels are directed in their 

 growth and location by the position of the veins, but are not limited in their distri- 



