In this treatise on hysteria and hypochondria, Willis showed that hysteria was a nervous disease and not a uterine disorder as had been traditionally believed. He compared hysteria in women to hypochondria in men. He considered the key feature of hysteria to be the “fit” or episodic disturbance of sensation short of “universal convulsions” and classified it under convulsive diseases. This caused hysteria to be linked with epilepsy as in Charcot’s hybrid, “hystero-epilepsy”.