This fabulous article was actually written last year and published in the November 26th edition of Science magazine. In it, we learn that a cat "exploits fluid inertia to defeat gravity and pull liquid into the mouth. This competition between inertia and gravity sets the lapping frequency and yields a prediction for the dependence of frequency on animal mass." This series of photos demonstrates how fluid adhesion occurs on the dorsal side of the tongue causing a column of liquid to form before the cat closes its mouth. Milk gets pulled up by the underside of the tongue. Only the tip touches the milk but doesn't penetrate it (unlike in dogs). Pretty amazing...and it looks so simple!
You can watch this process in the 1940's video below - minute 4:30.