Sentence:  As retinal images are conceded to <WSD>be</WSD> an integral function of the brain it seems logical to suppose that the nerves , between the inner brain and the eyes , carry the direct drive for cooperation from the various brain centers - rather than to theorize on the transmission of an image which is already in required location . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)