I encountered it five pages into Roland Barthes’ essay, “The Grain of the Voice,” which is in the collection Image, Music, Text. I was reading the version translated by Stephen Heath—it’s the most common edition, I think; the paperback has a pale yellow cover. “The Grain of the Voice” is about the distinction between two modes of singing. The first is an expressive, emotive mode (the pheno-song), which trains the listener’s attention on the meaning and emotional content of the words being sung; in the second mode (the geno-song), by contrast, the voice resonates at once abstractly and materially, focusing the listener’s attention on the singer’s enunciation of the sounds, not what they mean. Barthes bemoans the prominence of the former mode, which privileges the breath, identified with soul or pneuma, while mourning the dwindling prestige of the geno-song, which privileges the “grain of the voice,” as opposed to the “myth of respiration.”
It’s while reading a paragraph in which Barthes is criticizing the pheno-song, the style of singing that privileges the breath, that I encounter it:
“The lung, a stupid organ (lights for cats!), swells but gets no erection; it is in the throat, place where the phonic metal hardens and is segmented, in the mask that significance explodes, bringing not the soul but jouissance.”
I am used to reading literary theory. I am used to it being abstruse and opaque. But this was different. In the subsequent several hours that I puzzled over the phrase “lights for cats!” I passed through several distinct interpretative moods.
Given that the essay celebrates the “voluptuousness” of language separate from its communicative function, my first thought was that “lights for cats!” might be a Gertrude Stein style linguistic experiment embodying language’s phonic qualities. It doesn’t mean anything, silly!
- Paranoia (phase 1)
Because the phrase “lights for cats!” read to me like a non-sequitur, but also has a slogan-like quality like “votes for women!” the thought fleetingly but undeniably crossed my mind that this was a cry for help from Barthes’ cat. But cats can see in the dark, I reasoned. Why does Barthes’ cat need lights?
Rest assured that I quickly rejected both of these explanations and turned to Google, certain that this passage must have attracted considerable attention. I found that, indeed, these lines are frequently quoted, but that there was an odd quality to all these citations:
“Barthes dismisses the merely technical function of the lungs, ‘a stupid organ (lights for cats!)’ that ‘swells but gets no erection’” (John Potter, Vocal Authority: Singing Style and Ideology, 172).
“For instance, Barthes writes provoctively of the lungs as ‘a stupid organ (lights for cats!), swells but gets no erection,” which, in its dismissal both of the lungs as healthy and functioning, and worthy of dismissal, does present and confirm Tobin Siebers’s ideology of ability” (George McKay, Shakin’ All Over: Popular Music and Disability, 56).
“‘The lung, a stupid organ (lights for cats!), swells but gets no erection.’ In good Freudian tradition, however, let’s take this etymological play on words seriously. [Aha! At last!, I thought. But no.] Apart from the implicit reference to Barthes’s illness, which, because it affected his breathing, forced him to give up his singing lessons with Panzera, what we have here is the binary balance in the form of an association between breath and meaning: meaning given through the abstract soul in its opposition to the concrete body” (Diana Knight, Critical Essays on Roland Barthes, 256).
What all these commentaries have in common is that they conspicuously ignore the lights for cats.
This led to stages four and five in quick succession:
- Shock with shades of self-congratulation
No-one knows what this means. I have stumbled across a profound mystery. I am the first with the courage to admit it.
- Paranoia (phase 2)
Everyone knows what this means: it is self-evident and therefore unworthy of commentary.
- Admits Need for Help
This is when I texted EHA. In an extraordinarily generative and rapid-fire text exchange, and drawing on our combined powers of free-associating, Googling, and native wit, we came up with an ingenious, utterly convincing, and, as it turns out, completely wrong interpretation of the significance of “lights for cats!” one I was fully persuaded by for about two hours.
With the phrase “lights for cats!” we decided, Barthes underscores his contempt for the pheno-song by comparing it to the appeal of a moving point of light (like a sunbeam or a laser pointer) to a cat. He’s already said that the lung is a stupid organ, and he is personifying this stupidity in the image of a cat chasing light. There were, admittedly, a few problems with this interpretation. Was he saying that “lung” was to human as “lights” is to “cats”? But wouldn’t it more rightly be “sounds emanating from the lungs” rather than “lung” for that analogy to work?
- Niggling Seed of Doubt Remains
Even though I was now 99% totally sure that Barthes was saying that that the pheno-song is to humans as laser pointers are to cats, I decide that after all perhaps I should consult the original French just to be sure. (Note that reading something in another language is something of a last resort for me.) This is when I discover that the phrase in the original is not “les lumières des chats!” as I was expecting. Instead it is “le mou des chats”.
Le mou? What is this le mou? I look it up and “mou” means something like soft or limp. What??? Is this to do with lungs swelling but getting “no erection”? Is “mou de chat” French for “flaccid penis?” It has to be an idiomatic phrase, but when I look it up in Larousse, I get nothing. EHA asks her French friend who confirms that mou suggests softness not light.
- Paranoia (phase 3)
This is the only remaining explanation: the translation is wrong! I email a colleague who works on French theory to see if she can shed any light on either the original or the translation. In the meantime I give up on my quest and compulsively refresh the Guardian homepage for the rest of the night in order to see the British General Election results come in.
- Grudging admiration
Earlier in the afternoon I have casually mentioned to PBJ that I am struggling with this phrase. PBJ is on call tonight because he is an actual doctor. Somehow, in between dealing with psychiatric emergencies, he figures out both the meaning of “mou des chats” and why it is indeed correctly translated as “lights for cats!”
He texts me, “Le mou des chats is the lungs of an animal that a butcher will give to a client to take home and feed their cat.”
A minute later he texts me a definition of “lights”: “the lungs of sheep or pigs used as food, especially for pets.”
I look up “lights” in the OED and it’s even more definitive; it defines “lights” as meaning lungs as food “chiefly for cats and dogs.” 
And in French lungs as food seem especially identified with cats. The colleague I emailed had never heard of the phrase, but when I pass on the news she finds an entry from a French dictionary of proverbs from 1749:
“On dit encore que le mou est pour les chats; parce qu’on les nourrit avec du mou, qui est le poumon du boeuf.” [It is also said that ‘le mou’ is for cats; because one feeds them with it, that is with beef lungs.]
I was so sure that I was dealing with an analogy: that Barthes was saying lungs are to humans as lights are to cats. So it is kind of a shock to discover that lights literally means lungs; in fact, “light” and “lung” share the same etymology, lungs being so named for their lightness, i.e. their airiness. So it’s not a non-sequitur at all. It’s entirely in keeping with the language of breath and pneuma. It’s not surreal. It’s not a leap from one plane of meaning to another. No, it’s my brain that’s been leaping, chasing an ignis fatuus when there’s nothing really there. 
Stupid organ (lights for cats!).
 I discover from this definition that the phrase “living daylights” is a corruption of “liver and lights”
 Ignis fatuus, n. A phosphorescent light seen hovering or flitting over marshy ground, and supposed to be due to the spontaneous combustion of an inflammable gas (phosphuretted hydrogen) derived from decaying organic matter; popularly called Will-o’-the-wisp, Jack-a-lantern, etc. It seems to have been formerly a common phenomenon; but is now exceedingly rare.
When approached, the ignis fatuus appeared to recede, and finally to vanish, sometimes reappearing in another direction. This led to the notion that it was the work of a mischievous sprite, intentionally leading benighted travellers astray. Hence the term is commonly used allusively or fig. for any delusive guiding principle, hope, aim, etc. (OED)