DISSECTION OF THE PELVIS. 361 



between the lateral and superior muscles. [Besides the three muscles 

 now to be described, there is the compressor coccygis already dissected 

 (page 343).] 



The Erector Coccygis (sacro-coccygeus superior). This muscle arises 

 from the sides and summits of the sacral spines, and it is inserted by 

 e\iccessive short tendons to the upper aspect of the coccygeal vertebrae. 



Action.— Acting with its fellow, to elevate the tail directly ; acting 

 alone, to elevate the tail and incline it laterally. 



The CuRVATOR Coccygis (sacro-coccygeus lateralis). This muscle 

 seems to continue backwards the semispinalis of the loins. It arises 

 from the last two lumbar spines and from the spines of the sacrum, 

 and it is inserted into the lateral aspect of the coccygeal bones. 



Action. — To bend the tail to the side of the acting muscle. 



Fig. 48. 



Muscles of the Tail, deep Muscles oe the Hip, and Pelvic Licajients {Chauccaii). 



1. Erector coccygis ; 2. Curvator coccygis ; 3. Depressor coccygis ; 4. Compressor coccygis 

 5. Deep gluteus ; tj. Rectus parvus ; 7. Common tendon of obturator internus and pyriformis 

 8. Gemelli ; 9. Accessory fasciculus of the same ; 10. Quadratus femoris ; 11. Sacro-sciatic ligament 

 12. Great sacro-sciatic foramen ; 13. Superior ilio-s;icral ligament ; 14. Inferior ilio-sacral ligament. 



The Depressor Coccygis. Anteriorly this muscle consists of an 

 outer and an inner portion, Avhich Leyh describes as separate muscles. 

 It arises from the lower face of the sacrum, beginning about the 3rd 

 foramen. The slips of the inner portion are inserted into the first six 

 coccygeal A^ertebrse, while the outer portion extends to the extremity of 

 the tail, and is provided with strong tendons of insertion. 



Action. — It inclines the tail laterally or depresses it, according as it 

 acts alone or with the opposite muscle. 



