httpv://www.youtube.com/watch?v=12paEIC7BkU
The tongue presses the water against the roof of the mouth, and keeps it there even as the tip of the tongue sticks out for another lap. As the tip draws up another column, the trapped water from the previous cycle is shoved backwards, and eventually swallowed. By filming cats, Crompton and Musinsky showed that they do the same thing. The tongues of both species do several things at the same time – they draw up a fresh lot of water, while pushing back older ones up into their throat.