Marilynn K. Yee/The New York Times

Of the many great mysteries of the city street, perhaps none is more ubiquitous and more perplexing than the presence of so many black dots.

Even when one knows what they are — gum, walked on many, many, many times — it still seems impossible. Do people really chew that much gum? Do they really spit so much of it on the pavement, and do so many people really step in it on such a regular basis as to grind each one into a dark ovular stain?

“It’s not exactly an urban mystery,” Deborah Stead wrote in The Times in 2003. “More a case of mass denial, or a lack of anthropological curiosity.”

Gum on the ground is nothing new, as Ms. Stead points out, and there was even some amount of concern in the 1920s and 1930s that the whole city would one day be covered in a film of chewed-up rubber.

One hotel manager told The Times in 1921 that absent some effort at cleaning, the city might become totally enveloped. The prospect, she recounted, did not seem to upset one tourist couple from “Latin-America” who “remarked that they had never seen such delightful walks as were found here in spots. ‘Soft to touch, yet very firm.’ ” (One imagines the out-of-town visitor kneeling in his wool suit to push a finger into an early gooey spot.)

However, as far as can be determined, few if any formal studies have ever been made of the sheer tonnage or biological contents of the city’s gum deposits, though they surely contain enough dried DNA of past New Yorkers to populate, Jurassic Park-like, a whole other island – a place where stickball might still be played.

Fortunately, for those who tire of seeing the same speckled patterns, there is someone to call: GumBusters.

“Today when I see people chewing gum and throwing it on the ground, it’s very frustrating,” John Toussaint, 36, a gum-buster, says in a fun audio slide show about the service on Quirky NYC.

“I actually don’t allow my kids to eat gum anymore,” Mr. Toussaint adds.

The Brooklyn-based franchise, which has also been profiled on the television show “Dirty Jobs,” works with the Times Square Alliance and can be found busting gum with their (nonplasma) packs on most weekday mornings from 9 to 11. But the company traces its origins — like the city itself — to Holland.

While no sidewalk is gum-free, some are certainly worse than others.

So what’s the gummiest block in your neighborhood?

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