NERVES OF THE LUXG. 279 



bvane, which in fine bronchial tubes is continuous with that supplied 

 by the pulmonary artery ; (2) others form plexuses in the interlobular 

 areolar tissue ; (3) branches spread out upon the surface of the lung 

 beneath the pleura, forming plexuses and a capillary network. These 

 may be distinguished from the pulmonary vessels of the superficial 

 air-cells by their tortuous course and open arrangement, by their 

 being outside the tissue investing the lobules, and by ultimately ending 

 in the branches of the superficial set of bronchial veins.* 



•The bronchial veins have not quite so large a distribution in the lung 

 as the bronchial arteries, since part of the blood carried by the bronchial 

 arteries is returned by the pulmonary veins. The superficial and deep 

 bronchial veins unite at the root of the lung, opening on the right side 

 into the vena azygos, and on the lefc usually into the superior inter- 

 costal vein. 



Iiymphatics. — Part of the lymphatics of the lung take origin from 

 lymphatic capillaries in the interalveolar septa in the usual manner, 

 and where near the surface of the lung come mto connection with the 

 suhpJcural lymphatic plexus, previously mentioned (p. 273). They join 

 to form vessels which accompany the branches of the pulmonary artery 

 and vein, running on those vessels in twos or threes, connected by nume- 

 rous cross branches, and in some cases, becoming perivascular, even 

 completely surrounding the blood-vessel. The branched connective 

 tissue corpuscles with which these interalveolar lymphatics are in con- 

 nection at their origin, send processes upwards to the inner surface of 

 the alveoli, between the epithelial cells (like the pseudostomata of the 

 serous membranes, p. 198). 



Other lymphatics, which might be distinguished as bronchial, origi- 

 nate in the mucous membrane of the bronchial tubes, where the con- 

 nective tissue cells with which they are connected send up processes to 

 the surface as before. From the plexuses of origin they pass through 

 the muscular coat to be distributed in the fibrous layer, where they are 

 most numerous on the side opposite the accompanying branch of the 

 pulmonary artery. Here they not nnfrequently are found to enclose 

 nodules or follicles of lymphoid tissue, like those described under 

 " Serous Membranes." | 



At the root of the lung the superficial and deep lymphatics unite 

 into a few anastomosing trunks before entering the bronchial lymph- 

 atic glands. 



Nerves. — The nerves to the lung come from the anterior and pos- 

 terior pulmonary plexuses which are formed chiefly by branches from the 

 pneumogastric nerves, joined by others from the sympathetic system. 

 The fine nervous cords enter at the root of the lung, and follow the air- 

 tubes. Their final distribution requires further examination. Accord- 

 ing toRemak, whitish filaments from the parvagum follow the bronchia 

 as far nearly as the surface of the lung, and greyish filaments, proceed- 

 ing from the sympathetic, and having minute ganglia upon them in 

 their course, pass both to the bronchial tubes and pleura. Julius 

 Arnold has described the pulmonary nerves of the frog as ending in 

 pyriform ganglion cells. (Vn'chow's Archiv. vol. xxviii.) 



*■ A few small branches of tlie intercostal arteries also pass to the pulmonary pleura 

 and- surface of the lung through the ligamentum latum pulmonis (Turner). 



+ liurdon-Sanderson, Report of Medical Officer to the Privy Council, 1868. "Wywodzoff, 

 Wisuer Med. Jahrb. xi. lSti«. E. Klein, Proceedings of the Royal Society, January, 1874 



