Anatomically speaking, that's incorrect, as the great vessels and the heart itself are found in the mediastinum between the lungs. But it's certainly possible to run an arrow or a bullet through that way without opening them up. The nice thing about a cross-chest lung shot is that it'll cause both lungs to collapse. Nothing's going too far if it can't breathe. If a tension pneumothorax results, from the chest cavity filling up with air outside the lungs on attempted inhalation that can't go anywhere on exhalation, the increased pressure in the chest cavity will prevent blood from returning to the heart through the veins, effectively shutting down circulation even if there hasn't been a huge blood loss. Quick death results.

ricochet, those were my thoughts also and there is a lot of stuff there. Trouble is that most lie in line with the spine so if the spine is missed and the shot is not in line with the heart, there is a lot of empty nothing to cut. A little farther right or left of the spine and a lung or aorta branches will be cut (again if in line with the heart.) Slipping an arrow or bullet between the lobes of the lungs is a lot easier then I thought. If unsure of hitting the spine, I would aim farther from center.

Trouble is, letting one lung down isn't nearly as reliable a stopper as doing it to both. I'll bet we've got members on this board who've had one lung down.

ricochet, exactly right! That is why I will not shoot down at a deer anymore. If I can't get a broadside shot, the deer walks. Those shots happened a long, long time ago when I was just starting to hunt deer. Didn't take much to convince me those shots are no good. Deer have become so easy for me that any I can't get a good hit on are safe.
I feel the same about big bucks. Don't know how many I let walk to shoot a younger one or a doe. Oh, I have killed some nice ones, but always wind up giving the meat away. No sense shooting what tastes bad or is tough. I never figured out trophy hunters. My objective is always to have some good eating all year without trying to tenderize or cover up wild flavors. If I wanted to eat an old goat, I would buy one. Yeah I know, I will get bombed with responses telling me how good the 12 pointer tasted, but I know people that love old goat meat too. The smell of it cooking can gag a maggot.