An additional trigeminal system in certain snakes possessing infrared receptors

Abstract

This communication describes a nucleus and tract of the trigeminal system whose existence is not mentioned in any account of brain stem architecture known to the present author. The structures were first recognised in the brain stem of a giant snake (Python reticulatus) and later were also found in rattlesnakes (Crotalus cerastes and C. atrox), but not in the brain of a viper ( Vipera ammodytes).