Sentence:  A large majority of them bear evidence of long-continued habits of <WSD>fruitless</WSD> sucking in the deformity of the jaws, which is caused by some portion of the hand being placed in the mouth for the purpose of sucking it at a period of life when the bones were soft enough to yield to its pressure. 
Meaning of the word marked with <WSD> tags:  Unproductive, useless.