On the contrary, you can pass an arrow under the spine and not hit the lungs. This will depend on multiple factors, including the exhale/inhale state of the deer, the shoulder position, and the actual anatomy of the individual.

With that said, the arrow that passes under the spine and does not hit lung still punctures the pleural cavity. The pleural cavity, in mammals, is responsible for providing lubrication and maintaining air pressure for the lungs to properly inflate/deflate. Puncture this cavity and the animal will surely die, albeit a slow death, as the lungs will collapse given time. Basically the animal dies not to blood loss, but due to asphyxia.

There are hollow spots above the spine, and you can angle an arrow between the shoulder and vitals if the animals is steeply quartering away with his head down. You can also hit below the pleural cavity.

Other than that, it is merely a muscle shot that missed the vital region all together. If you hit behind the diaphragm you may actually miss vitals altogether, and the intestinal cavity is separated from the pleural cavity thereby protecting the lungs.

Many of these misses are dependent on the individual deer, anatomically, genetically and position-wise. The amount of fat on a deer also makes a difference, as subcutaneous fat is layed down within different reserve areas within each individual (hence, that' s why some men/women have a large butt and others have a large gutt!)


S&R