Turns out this question is significantly harder to answer than one might assume. For example, a great many of us could argue that the "me" is the stuff inside one's skin, but the microbiologists of the world would disagree.
Inside your body, there are 10 times more bacteria than human cells. Collectively, they take up as much space as your forearm, wrist and hand. The technical term for this legion is the "microbiome" and what we know about it is, honestly, not much at all.
One thing we do know is that most of us, if really pushed, would claim that even if we are not entirely our bodies, we are most certainly our thoughts and feelings. But candida albicans, a yeast infection in the stomach, is the counter-argument.
Under normal conditions, there is a balance between bacteria and yeast in your gut. Candida occurs when the balance tips, and yeast runs rampant. The condition has a number of nasty attributes, but foremost among them is a feeling of extreme anxiety. This happens because, when the body is anxious it craves the fuel needed to react quickly to negative situations. Sugar breaks down fast, so sugar is what's craved. But the reason the body is really craving sugar is because candida feeds on it. This means, at least under these circumstances, that your emotions are really just another's hunger.
Now does this happen under normal circumstances? No one knows for sure, but I was recently talking to Andrew Hessel, the co-chair of Bioinfomatics and Biotech at Singularity University, who is sure "there's plenty of communication between bacterial cells and our cells, even if we're not able to measure all of it yet."
On a similar note, we also know that eight percent of the DNA in the human genome consists of viruses that have inserted themselves into our genetic code. In fact, in a paper published in "Nature" last January, Cedric Feschotte, a professor of biology at the University of Texas, argues that this foreign DNA may contain the genes for schizophrenia and other mood disorders.
