o the accessory carpal bone (trapezum). The
other blends with the posterior annular ligament of the carpus.

The _ulnaris 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 metacarpi medius).

Acting together, these muscles flex the carpus or extend the elbow and
this action is antagonized by the biceps brachii (flexor brachii) and
extensors of the carpus and phalanges.

Etiology and Occurrence.--Inflammation of the muscular or tendinous
parts of the carpal flexors, does not occur as frequently as does
inflammation of the flexors of the extremity. They are subject to injury
such as is occasioned by hard work and concussion and contract as a
result; but, more frequently a congenital malformation of the leg is
responsible for undue strain upon these parts. Horses that are "knee
sprung" or that have a congenital condition where in the anterior line,
as formed by the radius, carpal and metacarpal bones, is bent forward at
the carpus, are subject to inflammation and contraction of the carpal
flexors. When these flexors are contracted, the condition is commonly
known among horsemen as "buck knee." In itself, inflammation of the
carpal flexors is not a condition which is likely to prove troublesome,
but because of carpal involvement (which is often present) the cause of
the trouble remains, and inflammation of the carpal flexors recurs or
becomes chronic and contraction of tendons results.

Symptomatology.--Inflammation of the carpal flexors, when acute and
uncomplicated, is characterized by a painfully swollen condition of the
affected tendons. No weight is borne upon the affected leg and the
carpal joint is flexed. Mixed lameness is present. There is no
difficulty encountered in arriving at a diagnosis because of the very
noticeably inflamed parts.

Many fully developed cases of contraction of the tendons of the carpal
flexors are observed where the condition has become established
gradually and no lameness has resulted from tendinitis or carpitis. In
some of these cases, subjects are stumblers and when they are carelessly
handled or kept at fast work over irregular or hard roads, chronic
carpitis with hyperplasia of the structures of the anterior carpal
region results, owing t