216 THE MUSCLES. 



tendons, which are inserted into each of the coccygeal bones. With regard 

 to their situation, these muscles are distinguished as sacro-coccygeus superior, 

 sacro-coccygeus inferior, and sacro-coccygeus lateralis. 



a. Sacro-coccygeus Superior. 

 (Synonym. Erector coccygis Percivall. } 



The fasciculi which form this muscle take their fixed insertion either 

 from the summits and sides of the three or four last processes of the super- 

 sacral spine, or from the coccygeal vertebrae themselves. The tendons 

 through which they effect their movable insertion into these vertebrae are 

 always very short. 



This muscle, covered by the coccygeal aponeurosis, in turn covers the 

 vertebrae it is designed to move. It responds : inwardly, to the analogous 

 muscle of the opposite side ; outwardly, to the lateral sacra-coccygeus, and, 

 near its anterior extremity, to a very strong aponeurotic expansion which 

 separates it from the transverse spinous muscle. It directly elevates the tail, 

 or pulls it to one side, according as it acts in concert with its fellow or 

 singly. 



b. Sacro-coccygeus Inferior. 

 (Synonym. Depressor coccygis Percivall.) 



This muscle is thicker than the preceding; its constituent fasciculi 

 take their origin from the inferior surface of the sacrum, towards the third 

 vertebra, and from the internal face of the sacro-ischiatic ligament and the 

 coccygeal bones. It readily divides into two parallel portions, which 

 Bourgelat has described as two separate muscles. The fasciculi of the 

 internal portion are inserted, by their posterior extremity, into the inferior 

 face of the first coccygeal vertebrae. Those of the external portion are all 

 furnished with strong superficial tendons, nearly all of which are for the 

 bones of the tail. 



This muscle responds : outwardly, to the ischiatic ligament, the ischio- 

 coccygeus and coccygeal aponeurosis ; inwardly, to the muscle of the opposite 

 side, and to the coccygeal attachment of the rectum ; above, to the sacrum, 

 the bones of the tail, and the lateral muscle ; below, to the rectum and the 

 coccygeal aponeurosis. 



It either directly depresses the tail or inclines it to one side. 



c. Sacro-coccygeus Lateralis. 

 (Synonym. Curvator coccygis Percivall. ) 



This muscle may be considered as the transverse spinous of the coccygeal 

 region ; indeed, it is confounded with that muscle of the back and loins 

 by its anterior extremity, and appears to continue it to the inferior 

 extremity of the tail. 



The fasciculi composing it have their origin from the spinous processes 

 of the last lumbar vertebrae, through the medium of the transverse spinous, and 

 from the coccygeal bones. The tendons terminating these fasciculi are deep 

 and not very distinct. 



It responds ; outwardly, at the posterior extremity of the ilio-spinalis, to 

 the inferior ilio-sacral ligament and the coccygeal aponeurosis; inwardly, 

 to the transverse spinous and the coccygeal vertebrae ; above, to the superior 

 muscle ; below to the inferior muscle, from which it is nevertheless 



