Modified version of diagram by
On one hand, there is a clear boundary between the brain and the body. Reach into a cracked-open skull, peel away its linings and you can pluck a brain right out of a head. And in school diagrams, it’s clear where the brain stops and the body begins. The brain is the worm-like ball of pink, sometimes with a tiny tail at the bottom, sometimes not, floating in the middle of the head. So in one sense, yes, in a diagram-sense, there is a clear boundary between the brain and the body, but that boundary is an illusion. Of all the human organs, the brain is the most difficult to contain.
There is another more important boundary to consider, a boundary as intricately detailed as the electric highway of nervous tissue penetrating the human body. The brain and the heart, for example, must somehow be connected, but in diagrams the tail of the brain always stops at the level of the neck. In reality, the brain is continuous with the brain stem and the spinal cord, both of which send out clusters of finely-branching nerves to every throbbing organ, the tip of every finger, every skin-covered surface in fact, not to mention glands and muscles. Nerves relay wonder and chaos and every shade of noise from the tongue, the eyes, the nose and the ears. The body is suffused with nerves. When we look at a diagram of the human head we see only two disconnected pillowy lobes, but if we were to crack open an actual head and try to pull the brain out, we would quickly discover that in order to remove the brain we must pluck it from its stem – its brain stem – and separate it from the rest of the nervous system it sends throughout the body. That is the crucial boundary.
The brain and the body are richly interconnected. I would go even further and say that the brain and the body are inextricably interconnected. A human being is an air-breathing volley of life forces echoing between the brain and the body, filtering information and experience through its tissues, tides in a singular ocean. How can you even try to draw a line there? Any dotted line separating the brain from the body is a lie. You would have to draw the line not only around the brain but also around the entire body, stretching the dotted line into a living web that coats the human body like a form-fitting glove. And even that glorious boundary would still be a lie.