MUSCLES OF THE RIBS 333 



magnus. It consists of two unequal portions, each having a separate 

 tendon. 



Origin. — From the outer and lower part of the humerus, the lateral 

 ligament of the elbow-joint, and the upper and outer part of the 

 radius. 



The two tendons of this muscle pass over a groove in fi-ont of the lower 

 end of the fore-arm, then over the front of the knee-joint, where they are 

 enclosed in a synovial sheath and bound down by the annular ligament 

 of the knee. On reaching the canon, the outer tendon joins with that of 

 the extensor suffraginis. The inner and main division proceeds downward 

 over the front of the large metacarpal bone to the fetlock-joint, where it 

 plays over a small synovial bursa. Lower down it is closely attached to 

 the OS suffraginis, or large pastern -bone, in the middle of which two 

 branches of the suspensory ligament — an inner and outer — ^join it. Thus 

 reinforced, it passes over the small pastern and enters the hoof 



Insertion. — Into the pyramidal process of the os pedis, or foot-bone. 



Action. — To extend the fetlock on the canon and the knee on the 

 fore-arm. 



Extensor Suffraginis. — A small muscle situated on the outer part 

 of the fore-arm, between the extensor pedis and the flexor metacarpi 

 externus. 



Origin. — From the external lateral ligament of the elbow-joint, and 

 from the external tuberosity and outer side of the radius and ulna. 



Insertion. — The tendon of this muscle, after passing over a groove on 

 the inferior and outer part of the radius or fore-arm, and through a synovial 

 sheath on the outer side of the knee, becomes united with the outer branch 

 of the tendon of the extensor pedis and a fibrous slip from the external 

 side of the carpus. Thus strengthened, it passes along the outer front part 

 of the canon-bone to the fetlock-joint, where it plays over a synovial bursa 

 and becomes inserted into the anterior and upper part of the first phalanx 

 or large pastern. 



Action, — To extend the fetlock on the canon and the knee on the 

 fore-arm. 



MUSCLES OF THE RIBS 



Serratus Magnus. — A broad fan-shaped muscle situated on the side 

 of the chest and partly concealed beneath the shoulder. 



Attachments. — Below, to the outer surface of the first eight ribs, by 

 a corresponding number of slips, which give it a serrated border from which 

 it takes its name. Above, to the under surface of the upper extremity of 

 the scapula or blade-bone. 



