Sentence:  There is some reason to think that thyroglobulin synthesis may proceed independently of iodination , for in certain transplantable tumours of the rat thyroid containing essentially no iodinated thyroglobulin , a protein that appears to be thyroglobulin has been observed in ultracentrifuge <WSD>experiments</WSD> ( Wolff , Robbins and Rall , 1959 ) . 
Meaning of the word marked with <WSD> tags:  the testing of an idea