96 GLANDS. 



vessels from a variety of sources (the bronchial and 

 pulmonary arteries, intercostals and internal mam- 

 maries), which enter at their attached surfaces. Fi- 

 nally, nervous filaments have been traced into their 

 substance from the great sympathetic, the nervus 

 vagus, and the phrenic nerve. 



The arteries distributed to the lungs are of two 

 sorts, bronchial and pulmonary arteries, The latter 

 accompany the bronchial tubes to their terminal 

 extremities, and, during their course, subdivide very 

 frequently, some of their branches going to the small- 

 est of the bronchise, whilst the rest terminate on the 

 pulmonary vesicles. Before they finally break up 

 into a capillary plexus, the smaller arterial branches 

 are found in the interstices between the lobules of the 

 lung, where they anastomose with each other in such 

 a manner as to surround each lobule with a vascular 

 circle or network, recalling the arrangement of the 

 branches of the vena portce around the lobules of the 

 liver. From this arterial circle branches of the small- 

 est size are given off in great number, which, by 

 their inosculations, form a capillary network with 

 exceedingly small meshes (sioth of a line in diameter), 

 which occupies the deep layer of the walls of the pul- 

 monary vesicles. Of. these ultimate branches of the 

 pulmonary artery, some leave the lobules to supply 

 the visceral layer of the pleura. 



veins. The radicles of the pulmonary veins, which take 

 their origin from the capillary plexus, spread them- 

 selves upon the surface of the pulmonary vesicles, 

 forming a stratum more superficial than the capil- 

 laries ; then they lose themselves in the lobular inter- 



