Your cat's little triangle-shaped ears are engineered to hear much more than you'll ever pick up. Almost everything about her ears plays a role in giving your kitty her keen auditory senses -- everything except her cutaneous marginal pouch, that is. Resembling a little pocket, or a slit, no one has discovered a purpose for this part of your cat's ear.
Now Hear This
Your cat's ears have three main parts: the outer ear, middle ear and inner ear. The outer ear is comprised of the pinna, the large triangular shaped flap, and the ear canal. The pinna receives sound waves and funnels them through the ear canal to the middle ear, where a collection of small bones send the vibrations to the inner ear. All the little pieces and parts -- the ear drum, the auditory ossicles and the cochlea -- work together to provide your cat with hearing that can pick up noise vibrating at 60,000 vibrations per second. As for that little pocket at the base of her ear, it has no real purpose, other than to make people speculate about its purpose. She can't store things in it, nor does she adorn it with jewelry. It is handy for the vet if he needs to collect tissue samples of the pinna, as is sometimes necessary if he suspects an illness such as the autoimmune disease pemphigus foliaceus. Otherwise, your cat's little pocket, casually referred to as Henry's pocket, is a normal part of her ear. To keep it and the rest of her ears healthy, keep an eye open for swelling, discharge, accumulation of dirt or discoloration, which can indicate infection. As well, if she scratches persistently, get her to the vet to have her checked; never stick anything in her delicate ears.