Here’s today’s
summary pic* (cobbled from Google Image searches). We’ll get to that a little
later, but first...
Did you know there
are two types of saliva? Stimulated saliva comes from the parotid glands and
flows when you chew. Doesn’t matter what you chew. It could be bone or a cotton
wad. Simulated saliva also helps to dilute acid in foods. This is a good thing
because acidic drinks (coffee and cola) start to dissolve the enamel in your
teeth. Unstimulated saliva, the viscous type (thanks to mucins) help to rebuild
your enamel. It also traps bacteria, thereby removing them when you swallow or gulp
them down. These facts, and other interesting stories, can be found in Mary Roach’s Gulp, subtitled Adventures of the Alimentary Canal.
Roach explores the
entire stretch of the canal, starting with your mouth and steadily moving to
the other end, with everything else in between. Her humorous footnotes provide interesting
analogies and factoids. For example: “The human digestive tract is like the
Amtrak line from Seattle to Los Angeles: transit time is about thirty hours,
and the scenery on the last leg is pretty monotonous.” Discussing the infamous ear-biting
incident of Mike Tyson, she writes: “Fear the fight bite: it can cause septic
arthritis. In one study, 18 of 100 cases ended in amputation of a finger.
Hopefully the middle one. In the aggressive patient, a missing middle finger
may be good preventive medicine.”
In Roach’s hands,
or pen, or imagination put to paper, saliva becomes fascinating. She muses
about why sores in her mouth don’t get infected, and then goes on to explore
how saliva is both “bacterial cesspool” and “antimicrobial miracle – the former
necessitating the latter.” She delves into the details of mouthwash, old
remedies advocating the use of saliva on countless ailments (some more gross
than others), why dogs lick their wounds, spitting for luck and blessing, and
enzymes in detergents. And all that’s packed in just one chapter, with breezy
engaging prose that is as informative as it is funny! (For those who prefer
zooming-in reading, it is Chapter 6: “Spit Gets a Polish: someone ought to
bottle the stuff.”
The chemistry and
magic enthusiast in me greatly enjoyed Chapter 12: “Inflammable You: fun with
hydrogen and methane.” No, we don’t have a sufficiently verified case of
spontaneous human combustion yet, in case you were wondering. But there are
potential cases of “inflammable eructation” – belching that can catch fire,
supposedly. For most people, a belch does not contain flammable gases. (Yes,
inflammable and flammable mean the same thing and are NOT opposites of each
other!) However in rare cases, there might be some evidence. You’ll have to
read it for yourself to find out! That’s because I want to get to cows, snakes
and mice.
When I discuss
combustion reactions and thermodynamic spontaneity in class, I have a go-to
illustration involving the dangers of lighting up a cigarette in a cow-field if
you’re facing a bunch of cow butts. Since my chemistry classroom has a natural
gas line, we could create a non-explosive environment containing methane and
oxygen, provided no one provides a source to trigger combustion. I put my hand
on the tap to the gas line as I describe my fanciful idea as a simulation. (I
don’t actually open the valve, but all the students are watching very closely, ready
to run.) We talk about what spontaneity means thermodynamically as we ponder
cows grazing in a field. (No, I have not looked up reports of spontaneous
bovine combustion.) My story even has a tie-in to biosignatures and the search
for extraterrestrial life. If a planet was found with an appropriately
proportioned mixture of methane and oxygen in its atmosphere, it might indicate
that living organisms were present and doing their best to stay away from
equilibrium!
Roach was also
curious about cows. Given that large quantities of methane are produced by
grazing cows, and that it would likely be “vented, as stomach gases typically
are, through the mouth. You would think that cow-belch-lighting would rival
cow-tipping as a late-night diversion for bored rural youth. How is it that growing
up in New Hampshire I never heard a cow belch?” Roach provides an answer (you’ll
have to read her book) as to why cows don’t belch but quickly moves on to a
more interesting story about snakes. They typically don’t belch either, but if
a python swallowed a cow or some other ruminant herbivore, they can create an
inflammable eructation, or a fiery belch.
How might this
work? Stephen Secor at the University of Alabama has a theory and supporting
experiments. Apparently, he fed rats to pythons in his lab and then measured
the amount of hydrogen gas exhaled as the rats were digested. There was a
hydrogen spike, but it came earlier than expected. (For my chemistry student
readers, picture hooking pythons to a gas chromatograph in lab!) I will now
quote Roach for parts of three paragraphs because her prose is simply unbeatable
in this story of her interview with Secor.
… Secor suspected [that] the hydrogen
spikes were the result of the decomposing, gas-bloated rat bursting inside the
python. “One thing led to another.” (Secor’s way of saying he popped a bloated
rat corpse and measured the hydrogen that came off it.) Suspicion confirmed.
The hydrogen level was “through the roof”. Secor had stumbled onto a biological
explanation for the myth of the fire-breathing dragon. Stay with me. This is
very cool.
Roll the calendar back a few millennia and
picture yourself in a hairy outfit, dragging home a python you have hunted. Hunted
is maybe the wrong word. The python was digesting a whole gazelle and was in no
condition to fight or flee. You rounded a bend and there it was, Neanderthal
turducken. Gazython. The fact that the gazelle is partially decomposed does not
bother you. Early man was a scavenger as well as a hunter. He was used to
stinking meat. And those decomp gases are key to our story. Which I now turn
over to Secor.
“So this python is full of gas. You set it
down by the campfire because you’re going to eat it. Somebody kicks it or steps
on it, and all this hydrogen shoots out of its mouth.” Hydrogen, as the you and
I of today know but the you and I of the Pleistocene did not know, starts to be
flammable at a concentration of 4 percent. And hydrogen, as Stephen Secor
showed, comes out of a decomposing animal at a concentration of 10 percent. Secore
made a flamethrowery whoosh sound…
With her slaying
the dragon of stilted, boring, academic prose, Roach has become my new
hero(ine), shining armor notwithstanding. She conveys knowledge with wit, and
turns arcania into engaging topics with just the right balance of humor.** I
merely give you a flavor; a tiny whiff at best. If the tip of your tongue has
been tickled, I recommend reading Gulp
in its entirety. A word of caution. It is not for the faint of heart, or more
accurately, weak of stomach. Roach does not skimp on the details of various
bodily parts and functions in the journey from one end of the tube to the
other. Topics you might think about in private but not discuss in public are openly
dissected by Roach.
While the book is
entertaining, it is also very informative, and I have learned plenty.
Especially from Chapter 14, which covers all things flatus. Three of the key
contenders to the stink are sulfur-containing gases: H2S, CH3S
and (CH3)2S. (Any wonder that hell is described with
brimstone?) But there are numerous other molecules that subtly contribute to
the smell. It turns out that one’s fart is akin to one’s fingerprint in its
uniqueness. So how do scientists go about testing and evaluating
odor-eliminating products? Roach poses an excellent question and then tells you
what Michael Levitt of the Minneapolis VA Medical Center did in his lab.
Which – whose wind – should represent the
average American’s? No one’s as it turned out. Using mean amounts from
chromatograph readouts as his recipe and commercially synthesized gases as the
raw ingredients, Levitt concocted a lab mixture deemed by the judges “to have a
distinctly objectional odor resembling that of flatus.” He reverse-engineered a
fart. This “artificial flatus” was put to work testing a variety of
activated-charcoal products…
Reverse
engineering a fart. Just picture it.
Roach has risen to
the top of my list of writing excellence I aspire to emulate. I won’t write in
the same style, but she has inspired me to think more carefully about the craft
of communicating complicated topics (such as chemistry!) in a way that is educationally sticky, while fostering further interest. Reading about the possible origins
of dragonflame makes me consider widening my gaze in writing a book exploring
the interface between magic and chemistry, one that is hopefully both
educational and engaging. (Here’s a potential Prologue to my potential Potions
book.)
Having read Gulp and discovered Roach’s writing
style, several of her other books are now on my must-read list, namely Stiff, Spook and Packing for Mars.
(Those are three different books.) I’m also considering using her “Inflammable
You” chapter as supplementary reading in my General Chemistry class next
semester. I’d been thinking about a new angle of my “Hiding in Plain Sight” theme: Gases. I’ve picked “Into the Blue” (from Sam Kean’s Caesar’s Last Breath) as a reading
to supplement the standard (potentially boring) textbook. Roach’s chapter nicely
adds to the Gases theme. Gosh, just thinking about it makes me all excited
about teaching! And on a weekend too.
So if you’d like
to be inspired, horrified, amused, and learn a bunch of cool and hot things
about, um, your alimentary canal, I highly, highly recommend Gulp.
*I put up a
summary slide before each class. Here are two examples.
**Other good science-y
books with doses of humor don’t quite have the exquisite balance and panache Roach
demonstrates. Examples I’ve read recently are in my blog posts on We Have No Idea, Spineless, and Soonish. (Those
are three different books.)
No comments:
Post a Comment