2177: Gastroenterology

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"Mostly it means that I'm acutely aware that the kid one table over coughed as the server walked past with our food."
Title text: "Mostly it means that I'm acutely aware that the kid one table over coughed as the server walked past with our food."


Gastroenterology is the study of the normal function and diseases of the digestive system: esophagus, stomach, small intestine, colon and rectum, pancreas, gallbladder, bile ducts and liver.

Antibiotics are substances that kill bacteria. They are effective at treating bacterial infections, including in the gut; unfortunately, they can also kill the normal gut bacteria. Probiotics are harmless or helpful bacteria which are sometimes used to replace the bacteria killed by an antibiotic. This reduces chances of re-infection by pathogens, and allows the natural gut microbiome to recover more effectively; comic 1471 was about the same theme. Probiotics are included in many foods, such as yogurt, as well as supplements, and are marketed as having health benefits.

The comic plays on the names probiotic and antibiotic. When matter and antimatter are mixed, they annihilate each-other, rapidly releasing energy (an explosion). This comic imagines a similar process when probiotics and antibiotics are mixed: Ponytail and a nurse runs into a room, with someone chasing after them, leading the nurse to exclaim that “they’re right behind us.” Ponytail mixes the probiotics and antibiotics, and throws the jar like a grenade, before continuing to run with the nurse. The reaction between the probiotics and antibiotics causes the jar to explode, presumably killing the pursuer. In reality, antibiotics and probiotics are often used simultaneously during treatment, but they are taken so that they do not mix (taken at different times or by different methods). Mixing them as in the comic, would just cause the antibiotic to kill the probiotic bacteria. Explosive reactions between antibiotics and probiotics are highly unlikely.[citation needed]

Matter and antimatter would react pretty much instantly upon mixing, not a short time later, as in the comic. (Also, one could not keep antimatter in a normal jar, or pour it in an atmosphere). The reaction shown is similar to the reaction between a strong acid and a strong base, which could cause an explosion after a short delay if kept in a tightly sealed container like a water bottle, as in the explosion here.

In the last panel, Ponytail is giving a more mundane summary of what gastroenterology is like (lots of paperwork). This is similar to Indiana Jones saying that archaeology is boring. The explosion sequence might be:

  • Ponytail's action fantasy of what the job could be.
  • Megan's fantasy, and Ponytail is telling her what it is actually like.
  • Real, and Ponytail is covering it up.

In the title text, Ponytail adds that her work makes her aware of a child coughing as the server was bringing food at the restaurant table, exposing the food to possible germs that could cause a gastrointestinal infection.


[The first five panels appear in a single row.]
[Ponytail, wearing a lab coat, and a guy wearing a scrubs hat rush in from the right side of the panel. Ponytail is holding a water bottle. There is a desk on the left of the panel with two jars.]
Hat guy: Hurry, they're right behind us!
[Zoom in on Ponytail, behind the desk, pouring the two smaller jars into the water bottle.]
An arrow points to the left jar: Probiotic
An arrow points to the right jar: Antibiotic
[A borderless panel. Zoom out on Ponytail shaking the water bottle to mix the two substances.]
Shake Shake Shake
[Ponytail throws the water bottle toward the right side of the panel, at something off-screen.]
[Hat guy and Ponytail run toward the left side of the panel, as the water bottle explodes.]
[The last panel is the only panel in its row, appearing at the far right end of the row and slightly narrower than the fifth panel above it.]
[Megan and Ponytail sitting at a table, facing each other, having a meal.]
Megan: So what's gastroenterology like?
Ponytail: Pretty boring. Lotta paperwork.

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I hope they are not eating italian, you never know what might happen if pasta and antipasta meet. Arachrah (talk) 16:23, 17 July 2019 (UTC)

Yea I figure this is a matter / anti-matter joke. Cgrimes85 (talk) 16:55, 17 July 2019 (UTC)
This antimatter explanation lacks the usual "punch" that I would expect from XKCD on a science joke. It's unsatisfying because the comic lacks any (other) reference to physics or space. My best guess is that it's a pun based on an alternate interpretation of the word "gastroenterology." Could some part of the word be re-used (or commonly used) in another, more explosive context? Could the explosion refer to methane production by the body? Or is it somehow a joke about a movie, or the general movie trope of making scientists into action heros? Jpaugh (talk) 14:41, 18 July 2019 (UTC)
It's playing on the general idea that mixing opposites often results in a violent reaction. Acid/Alkali or Matter/Antimatter. In a sense, probiotics and antibiotics are opposites - and in the (evidently very boring) world of gastroenterology - this is about as exciting at it gets. Obviously, the actual reaction between such things would be very slow and exceedingly un-exciting. SteveBaker (talk) 13:58, 19 July 2019 (UTC)

Current transcript says "Cueball" is the second character in the first and fifth panels. I don't think that's usually how it's done for a character wearing a hat, so I was thinking he should instead be named something like "Beanie Guy" or similar. Ianrbibtitlht (talk) 17:21, 17 July 2019 (UTC)

I think the hat looks like a surgical scrub cap[1]. Rtanenbaum (talk) 22:45, 17 July 2019 (UTC)

Saying the final panel is a lie is just one possibility. The 5th panel below can potentially mean the "reality", as opposed to the 4 panels above that's a fantasy/joke. Almost all jobs have this "what people think I do" and "what I really do" gap. Another possibility: I thought I saw in old cop/secret agent movies a common joke is when a character gets into a lot of action - and thus cause a lot of trouble - that person will need to write a lot of paperwork for the damage caused. Then the character will say "this job is boring. Lots of paperwork." Sorry I can't find an example right now but I seemed to remember seeing the joke multiple times.

It's hard to appreciate gastroenterology jokes if you've ever had a colonoscopy.Barmar (talk) 17:44, 17 July 2019 (UTC)

I disagree, & I'm holding back a bunch of bad puns about it. ProphetZarquon (talk) 18:02, 17 July 2019 (UTC)

I see a thematic connection with the comic about appendicitis treatment, although this could be about an unrelated ailment. 18:01, 17 July 2019 (UTC)

Current explanation says 'over-coughing'. What's that? a kid one table over, coughed. 10:22, 18 July 2019 (UTC)

Fixed! (Did you know they just hand out logins?) Jpaugh (talk) 14:53, 18 July 2019 (UTC)

"Another possibility is that the sequence refers to a reaction between an acid and a base," WHAT? No. They're specifically labeled! Where did "acid and base" even come from? Why not "Yin and Yang" or "White meat and dark meat"?? 10:46, 18 July 2019 (UTC)

I think the editor meant that the sequence is comically pretending that the mixing of probiotics and antibiotics gives a similar explosive effect to an acid/base reaction (or a matter/antimatter reaction) - they're not saying that that's literally what's happening. They're explaining the possible inspiration behind the cartoon logic. Hawthorn (talk)
And now the explanation covers that nicely. Well done. 09:49, 19 July 2019 (UTC)

It seems possible that the fantasy as a whole is a reference to a scene in the series Breaking Bad, in which Walter White substitutes fulminate of mercury for crystal meth, then uses it to cause a(n unrealistically large) explosion in the office of a rival. However, similar scenes can be found in earlier shows and films (e.g., the show MacGyver has several instance of such), so it may not be a reference to this specific one. 17:29, 18 July 2019 (UTC)

Any take on the meaning of the abundance of white space in the lower left part of the comic? Spongebob (talk) 15:17, 18 July 2019 (UTC)

My take is that it's a narrative device: the white space in which nothing is happening represents the two people just quietly eating, in stark contrast to the action-packed scene above. Hawthorn (talk) 19:46, 18 July 2019 (UTC)
It's almost as if the first row of frames is in a "think balloon" within the last frame. SteveBaker (talk) 13:58, 19 July 2019 (UTC)

My preferred interpretation is that Ponytail is to Gastroenterology what Indiana Jones is to Archeology... A usually boring field but Ponytail's / Indiana's versions are secretly more exciting. :) And Ponytail is keeping the exciting part to herself, just sharing the standard part. (Actually, now that I write that, I wonder if that's what Randall was going for) NiceGuy1 (talk) 05:43, 20 July 2019 (UTC)

In a sealed container prebiotics and probiotics would generate CO2 and explode, although it would take a while and likely not be a large explosion. As said antibiotics would likely just kill the probiotics.BlakeFelix (talk) 13:45, 22 July 2019 (UTC)

I think you'll find Gastroenterology is the study of the words used to describe the high quality food found in a moth's stomach :-) --OliReading (talk) 12:28, 30 July 2019 (UTC)