LIGAMENTS AND MUSCLES OF THE HORSE. 29 



3. Serratus Anticus. 



Origin.— From the dorsal spines, 2n(] to 13th inclusive. 

 Insertion.— To the anterior border and external surface of the 



nine ribs posterior to the 4 th. 

 Action. — It assists in inspiration, by drawing the ribs forwards. 



4. Serratus Posticus. 



Origin.— Yvom the last seven dorsal spines, and first two lum- 

 bar. 



Insertion. — To the posterior border and external surface of last 

 nine ribs. 



Action. — It assists in expiration. 



Note. — The two preceding muscles constitute the superficialis 

 costarum of Strangeways. 



5. LONGISSIMUS DoRSi. 



Origin. — From the inferior surface of the ilium anterir>r to the 

 sacro- iliac articulation, first two bones of sacrum, dorsal 

 and lumbar spines and supraspinous ligament 



Insertion. — To the transverse and oblique processes of the lum- 

 bar, transverse processes of the dorsal, transverse and 

 spinous processes of last four cervical, and external surface 

 of last sixteen ribs. 



Action. — -Acting together, they are the great extensors of the 

 vertebral column ; acting singly, it inclines the spine to the 

 side of the acting muscle. 

 It may also assist in expiration. 



6. Transversalis Costarum. 



Origin.— 'Fyovh the transverse processes of the first two lumbar 

 vertebrae, and from the anterior border of the ribs, near 

 their angles. 



Insertion. — To the posterior border of the ribs, anterior to Ihe 

 14th, and to the last cervical transverse process. 



Action. — It draws the ribs backwards, thus assisting in expira- 

 tion. 



