Reis PM, Jung S, Aristoff JM et al: How cats lap: water uptake by Felis catus, Science 330: 1231, 2011.
Dr. Roman Stocker, an associate professor at the Massachusetts Institute of Technology, wondered about the mechanism cats use to lap fluid while watching his own cat one day. Out of that curiosity, a project to answer the question using high-speed video, simulations, and investigations of other feline species was born. Cats use an interesting biomechanical method to drink by bending the tip of the tongue downward toward the chin and pulling liquid into the mouth. The high-speed videos showed that cats don’t dip their tongue into the liquid to scoop it up as dogs do. Rather, cats touch the tip of the tongue, with the tip bent downward, against the surface of the liquid before drawing the tongue rapidly back into the mouth. The cat swallows only after several laps have accumulated enough liquid in the mouth.
Matson, J. Cat Lap: Engineers unravel the mystery of how felines drink. Scientific American, Nov 11, 2010.