Resin cast of the pulmonary arteries and bronchi supplying blood and air to the lung, viewed from the front. Clear resin was used to fill the airways, red in the case of the pulmonary arteries. The trachea (wind-pipe) branches into the left and right principal bronchi: the large pulmonary trunk divides into the right and left pulmonary arteries in front of the left principle bronchus. On the left of the image, the branch of the right pulmonary artery to the upper lobe of the lung is evident. The cast was made by pumping resin into the airways & arteries, allowing them to set, & cleaning with sulphuric acid.