Isn't it amazing, this human body. I've paused on occasion to wonder what it is about the number five that seems so integral to our construction. Five fingers, five toes, sure. But more to the point, it seems, five major limbs or extensions protruding from the core. Two arms, two legs, and ... the head. It's funny, isn't it? You can lop off a foot, a hand, an entire arm or leg - and you still have a person. Somebody who could talk to you, ponder the nature of the world... engage in a game of chess.
Inside the core, things are more vital but still not absolutely critical to the total package. We have transplanted lungs, installed the liver of a pig, invented dialysis machines to do the job of a kidney... we've even had a person live for a while with a mechanical heart pumping the blood through the system.
But not the head.
The head sits atop the structure and contains the brain. That pulsing few pounds of gray matter contains billions of synapses, firing at light speed twenty four hours a day, sending messages throughout the various lobes and (if still connected) down the pathways to the rest of the limbs and receiving signals back in return. Take this away and you lose the person, even if the rest of the bits are intact and functioning. Without that one limb, as it were, the functional whole fails. No communication, no pondering, no chess... the system won't even continue to breath or pump blood of its own volition. It simply stops.
The same formula applies to mammals of all sorts. Also to birds, reptiles, and virtually everything that follows the five limb format. There's that number five again - so important - but why? Certain insects who come from a seven limb family can have the head portion removed and function for quite some time. Worms and their kin can often be lopped in half and will grow two new worms from the detached portions. They seem to only have one limb to begin with.
What does it all mean? I have no answers for you. Only questions to ponder.