Fig. 54.--Muscular system of the human foot. 1, Tibialis anticus and extensor proprius pollicis. 2, Extensor longus digitorum. 3, Tendon of peroneus tertius. 4, 5, Peroneus longus and peroneus brevis. 4′, 5′, Tendons of the same. 6, 7, Tendons of the extensor longus and extensor brevis digitorum. ] The flexor brevis digitorum displays perforated tendons, belonging to the second and third toes. The flexor longus digitorum displays perforated tendons for the fourth and fifth toes. The flexor longus pollicis divides into two tendons, one of which goes into the toe itself, while the other is connected with the flexor longus digitorum, and displays perforated tendons for the third and fourth toes, while the perforated tendons of the second and fifth toes have their origin in the other flexor. [Illustration: Fig. 55.--Muscles on the upper side of chimpanzee’s foot. 1. Tibialis anticus muscle. 2, Extensor proprius pollicis. 3, Extensor communis digitorum. 4, 5, Peroneus brevis and peroneus longus. 6, Tendon Achilles. 7, Extensor brevis digitorum. 8, Slip of the same for great toe. 9, First dorsal inter-osseous muscle. 10, Adductor pollicis. 11, Abductor minimi digiti. ] In the gorilla the lumbricales muscles of the foot are powerful. The first inter-osseous muscle is likewise well developed and bicipital. There is a short flexor and an abductor for the little toe. I have not yet been able to assure myself of the existence of an opponens for that toe. In the chimpanzee the muscular system of the great and little toe does not essentially differ from that which we have described in the gorilla. The flexor brevis digitorum forms the perforated tendons of the second and third toes. The flexor longus digitorum provides the fourth and fifth toes with perforated, and the second and fifth toes with perforating, tendons, while those which belong to the third and fourth toes have their origin in the flexor longus pollicis. As in the gorilla, the latter muscle produces a fibrous investment for the tendons of the flexor longus digitorum. In the orang there is an abductor of the great toe, a very slightly developed opponens, a short bicipital flexor, and an adductor. One of the long flexors of the toes appears to represent the flexor longus pollicis in man. It provides the second and fifth toes with perforating tendons, while those of the third and fourth toes have their origin in the other flexor longus digitorum. There is no long flexor tendon on the great toe. The perforated tendons in this case generally belong to the short flexor muscle. In addition to the perforated tendons of the fourth toe, there is the long flexor already described.