Sentence:  Although Miller noted in 1907 that a difference in the pleural blood supply existed between animals , nowhere in his published works is it found that he did a <WSD>comparative</WSD> study of the intrapulmonary features of various mammalian lungs other than in the dog and cat ( Miller , ' 13 ; ' 25 ) . 
Meaning of the word marked with <WSD> tags:  relating to or based on or involving comparison