Well, cats' tongues are covered in little spines. Called "papillae," they look like little hooks and are made of keratin, like human fingernails.

Researchers collected tongue samples from six species (domestic cats, bobcats, cougars, snow leopards, tigers and lions) and subjected them to a micro CT scanner for a closer look and discovered the existence of an internal cavity in each papilla.

These cavities help us collect saliva from the mouth and distribute it on the fur through licking when using the toilet, it also helps when drinking water.