When you give a big sugar-like molecule called hyaluronan to rats and dogs by mouth, it spreads through their bodies in a different way than a radioactive substance called technetium pertechnetate...

When rats and dogs swallow a special kind of slippery molecule labeled with a tracking dye, the dye shows up in their skin, bones, and joints a day later—but a different tracking dye (technetium) doesn’t show up anywhere.

When rats and dogs swallow a big molecule called hyaluronan, their bodies absorb it and it shows up in places like their joints, spine, and saliva glands—and it stays there for almost two days.