They sometimes go from the fore side of the superior descending aorta, at others from the first intercostal, or from the arteriae oesophageae. Occasionally they arise separately from each side to reach each lobe of the lungs, and sometimes by a small common trunk, which afterward separates towards the right and left hand, at the bifurcation of the aspera arteria, and the branches accompany the ramifications of the bronchia.

The bronchial artery on the left side often comes from the aorta, while the other arises from the superior intercostal on the same side; which variety is owing to the situation of the aorta. Sometimes there is another bronchial artery, which goes out from the aorta posteriorly, near the superior intercostal, above the bronchialis anterior.

Communications have been observed between the bronchial artery and the vena azygos, and with the coronary artery of the heart. Ruysch first discovered these vessels, and he describes both the bronchial arteries and veins in his fourth epistle.

Bronchiales glandulaeat the angle of the first ramification of the trachea arteria, we find on both the fore and back parts certain soft roundish glandular bodies of a bluish or blackish colour, and of a texture partly like that of the thymus, and partly like that of the thyroid gland. There are many similar glands at the origin of each ramification of the bronchia. Dr. Hunter supposes their office is to separate a mucus to lubricate the lungs: they are different both in colour and structure from the conglobate and lymphatic glands.