Daniel Paul Schreber, Memoirs of my Nervous Illness, n.57
If the cells that constitute the thing you normally consider to be your body could vote, every initiative on the ballot would be about unchecked reproduction and parasitic greed. This is because the bacterial cells which colonize the interior and exterior surfaces of your anatomy (which are really a single surface; every vertebrate body is basically a very convoluted donut,) outnumber your "own" cells significantly. Mammalian, eukaryotic cells are an elite minority which can dictate policy because our tissues are organized into various layers of oligarchy, all concerned with perpetuating their own hegemony as a class, (and a powerful subset of which is explicitly dedicated to repressing and marginalizing bacteria); if simple democracy obtained on the cellular level and turnout was uniform between prokaryotes and eukaryotes, you would find yourself at the mercy of an implacable and eternal majority of unicellular anarchist libertarians, contemptuous of the resources allocated to the ponderous, overgrown liver for the sake of producing glucose to feed freeloading brain cells, and of the repressive authority invested in the hated killer T-cell.
During a biology class I took in college, as a practical experiment, we all cultured our own commensal bacteria. What was immediately apparent upon cursory examination of the resulting agar plates (aside from the anti-welfare messages the furry little colonies had spelled out with their secretions) was that a lot of the smells that one associates with humanity are actually produced by bacterial metabolism. My roomate Chris Jillson's plate smelled like your face smells after a long journey. This is a general phenomenon: bad breath has nothing to do with "your" mouth; it's produced by bacteria living there which metabolize the exogenous and endogenous sulfur-containing compounds they find ther to create new, foul-smelling molecules. Likewise "B.O."; the odor we try to suppress with liberal slatherings of aluminum salts isn't wholly ours; in large part, it's the excresence of innumerable microscopic bugs eating our sweat. The same applies to decomposition, which isn't so much a separate process from life as one logical extreme of its organizing principles. Bacteria feeding on corpses, not the corpses themselves, produce such fragrantly named substances as "putrescine" and "cadaverine".
Smell, as is commonly known, is one of the more evocative senses, and there's a neuroanatomical correlate for this: the olfactory nerves, unlike the nerves which transmit and transduce most of your other senses, are plugged directly into the limbic system, an ancient and scary group of structures in the bottom of the brain which mediate powerful, atavistic affective states. (Incidentally, there is an emphatically non-commensal free-living amoeba called Naegleria fowlerii which exploits this connection in a particularly grisly way: it latches on to the exposed olfactory nerve endings in the roof of the nose and crawls up them into the brain, where it multiplies freely and feeds on your very being, producing a fulminant and almost uniformly fatal illness which begins with olfactory hallucinations and ends, a few days later, in abject brain death. You get it from swimming in fresh water. It lives everywhere.) The limbic system is also integrally involved in the formation of new memories, which accounts for the nostalgic power of scent. Everyone has had the experience of being transported back to a distant period in their past, in near hallucinatory detail, by a whiff of one of that time's characteristic odors. It has occurred to me that I might start trying to exploit this by prospectively identifying periods which I would later like to be invested with that immediacy of memory and picking something singular to sniff regularly during that time, so that I could conjure each forgotten milieu at will later simply by digging, say, the little sachet of opium I carried around during my time in Bognor Regis out of some elaborate card-catalogue and inhaling deeply.
Now, a lot of this (a circumscription I vehemently maintain includes my towel) is explicable by appealing to our general mania for recognition. Humans are compulsive about this: we see spectral figures standing over our beds in the night which we know to be our own wardrobes, we hear voices in the pounding surf, we recognize the faces of old acquaintances on crowded buses in distant cities, we think the New Testament is about us. I smell Mr. B on the towel because something in me is hard-wired to prefer familiar interpretations, however gnarly, to radically alien phenomena like the highly specialized smelly molecules the bugs in my towel (which I have already burned, thank you) are (were! were!) busy producing.
However, this interpretation is also a happy fiction. In fact, it is inescapably the case that I am daily taking on small inocula of my patients' commensal flora; after all, every morning I lay my hands upon them, under them, around them. I ask them to breath deeply and to expel whatever facultatively aethereal organisms are living in their mouths onto my person. I usually don't wear gloves or a gown, and even if I did the efficacy of such paraphenalia would be questionable. As Lister proved, the only way to really sterilize a normal environment, outside of a rigorously controlled modern operating theater, is to fill the air with a fine mist of carbolic acid. It would be ridiculous to imagine that somehow my native flora are such a hardy master race of Aryan super-bacteria that they effortlessly deflect the miscegenating influence of Mrs. S.'s epidermal menagerie. On the contrary, it is only reasonable to expect that I and represent an undiscovered, (and, I like to think, more vibrantly appealing) continent for them to explore. Like bold space explorers (or maybe rats from a sinking ship) they take that giant leap to the brave new frontier that is my exterior surface and start gnoshing on my exfoliated cells, continuing their definite way of life and elaborating the aromatic hydrocarbons which they are accustomed to produce and in which, one imagines, they take an admittedly provincial but nonetheless fierce pride, like Swedes do in that horrible fermented herring stuff you're no longer allowed to carry on planes.
Sometimes, I smell Mrs. S. when I scratch my ear.
This gives one a new perspective on the distinctive smell of any given hospital ward. You can also tell them apart in the dark. Each is a gestalt entity, and has its own distinctive smell, which is partly disinfectant and hospital "food", but is more noticeably exhaled by the rainforest of its inmates' diverse microflora. Over time it changes, as they come and go, producing an evolving great cloying symphony which is the product of perhaps thirty or forty individual concatenations of scent, some pathological, some natural, some the product of neglect, some deliberately cultivated. Each patient is a section in the orchestra. Mrs. S. is brass. Mr. B. is percussion. And, of course, they cross-pollinate; the scions of the first violin get restless and strike out for the promised land of wind. We know this is happening all the time, and how difficult it is to prevent, by observing what happens with the infinitessimal percentage of bacterial species that we keep track of because they cause hospital-acquired infections (to strain the orchestral metaphor here, Clostridium difficile is a chainsaw set loose among the woodwinds).
It is really the case, then, in a biologically determinable sense, that we are contingent on and contiguous with one another, at least insofar as our fleshly communications enable the migrations of bacteria which, remember, outnumber us within our own bodies. The distribution of genes capable of or actively elaborating the proteins which produce "our" bodies are in flux. The thirty-thousand odd genes tightly packaged in the big, expensive nuclei of our huge cells are actually in the minority as the intrepid colonies of bugs we unconsciously cast upon each other grow like ripples on our skin and in our guts, only to be gradually subverted and supplanted by other nuclei of wildly multiplying creatures producing their own highly specific molecular plumage. It is probable that the reason I smell Mrs. S. when I scratch my ear is that the things that make her smell the way she does are actually living on my ear. To take a more universal example: the process of disentangling yourself from a romantic relationship goes on long after you have really, finally, with a bathos that defies all attempts at romanticization, decided that you just don't care about that person anymore. His or her commensal flora are still breeding in your secret places, elaborating the intimate perfumes of your first excited encounters in dark silence.
All this stuff about smelly bugs, which is fascinating in a twelve-year-old-boy kind of way, should really come as no surprise since it illustrates the same dynamics that create who we (think we) are in a much more immediately important way. An analogous proliferation and wild, often random migration of arguments, trains of thought, ethical committments, jokes, myths, and other micro-organisms of consciousness, whose operations are even more subterranean and difficult to elucidate as those of bacteria, come together to constitute the shifting terrain that is our subjectivity. I am now, statistically, commensurable with Mrs. S. from the point of view of some hypothetical Martian biologist because, if you were to grind me up and analyze the distribution of genes that constitute whatever it was that you ground up, you would discover (in addition to the 99.999% of human genes we share,) specific genetic and proteomic patterns attributable solely to the (smelly) bacteria we now host in common. But, and of much more immediate relevance to me at least, a Martian anthropologist would discover the same to be the case of our internal narratives. Mrs. S.'s occasional delirious assertions that if I she can just "get my hands around your scrawny neck, you're going to know about it" have infected my subconscious, where they are multiplying and mutating and will, presumably, eventually find some point of egress onto some other fertile narrative ground. Hopefully I will not actually strangle anyone. Mr. B.'s dry, irritable, flat sense of humor is colonizing my own; I am already stealing his poingnant, depressing jokes. These are superficial examples, but what I'm trying to indicate is that just as the integrity of our bodies is called into question by the gigantic population of helot bacteria they environ, so the identity we like to think is ours is pervaded by other dimly guessed at (and sometimes really pungent) influences.
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