The first set has three enamel layers, increasing to ten layers in the sixth set. Literally the animal's lifeline, it is used for eating, drinking, dust and water bathing, as well as communication. Vision is poor. Long lashes and nictitating lids protect the eyes from dust. Hearing is acute.
Elephants have the largest brain size versus body weight other than man.
These statistics are used to distinguish instinctive from learned behavior, and are examples of higher intelligence. Endangered because of loss of habitat and because of poaching for ivory. Animal Life Encyclopedia, Van Nostrand Reinhold, New York. Among the Elephants. Portraits in the Wild.