56 LIGAMENTS ANJ) MUSCLES OF THE HORSE. 



Insertion. — To the semilunar crest of the os pedis. 



Action. — To flex the coffin, pastern and fetlock joints, and to 

 extend the hock in succession. 



JVote. — This muscle is indistinctly divided into outer and inner 

 portions, with two tendons. These soon unite and pass 

 through the tarsal sheath. The tendon below the hock is 

 joined by the check ligament, which is not so strong as 

 that of the fore limb. Below this the arrangement is 

 identical with that of the fore limb. 

 6. Flexor pedis accessorius. 



Origin. — From the external tuberosity of the tibia. 



Insertion. — It joins the perforans, after passing through a syno- 

 vial theca at the inner side of the tarsus. 



Action. — To assist the deep flexor. 

 Tarsal Sheath. 



This is a tubular passage at the back of the tarsus. It is 

 bounded anteriorly by the posterior common and tarso- 

 metatarsal ligaments, externally by the os calcis, and pos- 

 tero-internally by a fibrous band. It is lined by a synovial 

 membrane, which is reflected on the flexor tendon, extend- 

 ing upwards two or three inches, and downwards below the 

 middle of the metatarsus. (Distension of this sac is known 

 as "thorough-pin"). 



METATARSAL REGION (unimportant). 



1. Extensor 2?edis hrevis. 3. Interossei (2). 



2. Lumhric (2). 



1. Extensor pedis brevis. 



Origin. — From the os calcis and astragalus. 



Insertion.— It joins the tendons of the extensor pedis and per- 



oneus at their angle of union, to which its 

 Action. — Is auxiliary. 

 The lumbrici and interossei are exactly similar to those of the 



fore limb. 



