The Seventh Men were pigmies, scarcely heavier than the largest of terrestrial flying birds. Through and through they were organized for flight. A leathery membrane spread from the foot to the tip of the immensely elongated and strengthened "middle" finger. The three "outer" fingers, equally elongated, served as ribs to the membrane; while the index and thumb remained free for manipulation. The body assumed the streamlines of a bird, and was covered with a deep quilt of feathery wool.
Source: tatoeba (10579907)