Guys, I am going to have to disagree with you, respectfully of course.
There is a void in the body cavity. It is not as large as some people will lead you to believe and is near impossible to hit from a tree, but it is there. My family owned a meat processing house for years. There have been hundreds of deer come in that have scar tissue from pass through shots from bows and guns that dont touch anything.
Bill is correct when he talks about the large artery below the spine, it is as big as your thumb. Right below that artery and above the lungs is nothing. It is only about 2" average hight, but it is there. Scar tissue don't lie.
God Bless,
Nathan