Sentence:  This connection was clarified by Smith and Smith ( 1922 ) , who showed that saline extracts of fresh bovine <WSD>pituitary</WSD> glands could re-activate the atrophied thyroids of hypophysectomised tadpoles . 
Meaning of the word marked with <WSD> tags:  the master gland of the endocrine system; located at the base of the brain