... lateralis (flexor metacarpi externus) has its origin from the lateral epicondyle of the humerus and inserts to the proximal extremity of the fourth metacarpal (outer splint) bone and by another attachment to the accessory carpal bone (trapezium) with the tendon of the flexor carpiulnaris (flexor ... — Lameness of the Horse - Veterinary Practitioners' Series, No. 1 • John Victor Lacroix