MYOLOGY 95 



Relations. — Infero-anteriorly with the anus. Posteriorly with the 

 edges of the ilium and of the ischium. Internally with the depressor 

 caudae. 



Action. — Gives support to the viscera in the post-anal region, 

 and aids in attaching the anus to the structures above. 



Depressor Caudae (Fig. 23, No. 6). Location. — The infero-lateral 

 side of the tail. 



Origin^ — From the lower half of the posterior border of the is- 

 chium, and from the entire posterior border of the post-pubis beyond. 



Insertion. — To the quill butts of the three or four outer main 

 tail feathers. 



Shape. — Strong, conical. 



Relations. — ^Externally, with the depressor coccygis. 



Action.—Shxgly, puUs the tail downward and outward; with its 

 fellow, pulls the tail downward. 



Depressor Coccygis. Location. — The outermost of the infero-- 

 lateral muscles of the tail. 



Origin. — From the lower half of the posterior margin of the ischiimi 

 and the anterior three-fourths of the posterior margin of the post- 

 pubic element of the pelvis beyond it. 



Insertion. — To the thickened rim of the inferior and expanded 

 portion of the pygostyle. 



Shape. — ^Flat, triangular. 



Relations. ■^-Jntermilly with the depressor caudae. 



Action. — Singly, pulls the tail downward and to one side; with its 

 feUow, puUs the tail downward. 



Lateralis Caudae (Fig. 23, No. 5). Location. — The lateral side of 

 the taU. 



Origin. — From the tip of the transverse process of the first free 

 caudal vertebrae. 



Insertion. — To the outer three quiU butts of the main tail feathers. 



Shape. — Four fascicuh forming a fleshy beUy. 



Relations. — Inferiorly, with the levator caudae and superiorly with 

 the depressor caudae. 



Action.- — ^Singly, pulls the tail downward and outward; with its 

 feUow, pulls the tail downward. The outermost fasciculus con- 

 tracting, spreads the tail feathers. ~ 



Lateralis Coccygis (Fig. 25, No. E, 2). Location. — The infero- 

 lateral side of the caudal vertebrae. 



Origin. — ^From the surface of the posterior end of the iUum and by 



