A comparative study of the lumbrical muscles in the hand

Human amd monkey hands were dissected, together with the forepaws of the dog, rabbit and kangaroo. These dissections showed that the human lumbrical muscle inserting into the proximal phalanx or dividing into two tails belongs to an atavistic anomaly. In the kangaroo, the first lumbrical muscle commonly arose from the long flexor tendon of the first finger and the deep flexor tendon of the second finger. This strongly suggests that these tendons (or M. Flexor pollicis longus and M. flexor digitorum profundus) are homologous.