Fig. 51.--Palmar muscles of man. _a_, Ligaments of wrist, especially the anterior ligament. _c_, _c′_, Sheathing ligaments. _d_, _e_, _f_, Oblique fibres of the ligaments of the sheath of the flexor tendons. 1, 2, Tendons flexor sublimis, and of the flexor profundus muscles of the fingers. 3, The reciprocal perforation of these tendons. 4, Continuation of the tendons of the flexor profundus of the fingers. 5, Tendon of the flexor longus pollicis. 6, Abductor pollicis. 7, 8, 9, Flexor brevis, adductor, and opponens pollicis. 10, 11, 12, Flexor brevis, abductor, and opponens minimi digiti. 13, Lumbricales. 14, First dorsal inter-osseous muscle. ] According to my own researches, the long abductor of the thumb in anthropoids forms a muscle not more considerable than one in proximity with it, of which the origin and more central direction recall the short extensor of the human thumb. In all four species I found that the abductor had two tendons, and was attached to the trapezium. The muscle in its vicinity is inserted above the base of the first metacarpal bone. I have not been able to discover an extra extensor of the thumb in the gorilla. The question now arises what we should think of the second muscle, which is found in these animals in the vicinity of the abductor. In my opinion, it may be confidently accepted as a short extensor of the thumb, since it always effects an extension of the metacarpal bone of that member, and in this act of extension it is supported by the long extensor which acts upon the phalanges. It must be remembered that the comparatively short thumbs of anthropoids have not to be employed in so many different ways as the human thumb, and that we cannot therefore be surprised that the development of the short extensor is less complete. A special extensor muscle of the index finger is either altogether absent in the gorilla or very slightly developed, while it is very apparent in _Hylobates albimanus_ (~6~, Fig. 53). In the chimpanzee this muscle sends a tendon to the middle finger. In the orang there is one extensor common to the four fingers. In the gibbon’s hand, this, as well as the other extensor and flexor muscles, is remarkable for its excessive slenderness. The manifold connections of the extensor tendons with each other are an interesting peculiarity (Fig. 53). [Illustration: