MYOLOGY 55 



M. longus atlantis (fig. 11) has origin from the trans- 

 verse processes of the third, fourth and fifth cervical verte- 

 brae, with insertion onto the caudal portion of the trans- 

 verse process of the atlas. In Teonoma origin seems to 

 be from the third and fourth vertebrae only. 



All of these deep, intrinsic back muscles save the inter- 

 spinals are innervated by the suboccipital nerve. 



E. Muscles of the tail 



Each half of the tail has two flexors, two extensors, and 

 two abductors, these being 



Mm. flexor caudae brevis extensor caudae lateralis 



flexor caudae longus abductor caudae externus 



extensor caudae medialis abductor caudae internus 



M. flexor caudae brevis (figs. 7, 12) has origin from 

 the ventral surface of all the sacral and first four or five of 

 the caudal vertebrae, close to the midventral line. The 

 several tendons developing extend caudad with those of 

 the flexor longus. 



M. flexor caudae longus (figs. 7, 12). The more 

 cranial portion of this powerful muscle lies deep (dorsad) 

 to the psoas magnus. Origin is from the ventral surfaces 

 of the centra and diapophyses of the vertebrae caudad 

 from and including the fifth lumbar. Numerous tendons 

 are developed which are inserted onto the caudal vertebrae. 



Better terms to use for the flexors of the tail in the lower 

 manmials would be anticus and posticus instead of brevis 

 and longus, but the more usual nomenclature is retained 

 for the present. 



M. extensor caudae medialis (figs. 6, 12) is the 

 muscle lying medio-dorsad upon the tail, it being a continu- 

 ation of the multifidis spinae. Origin of its fibers is from 

 the spinous processes of the sacral and a few of the caudal 

 vertebrae. Tendons developing are inserted onto the 

 dorsa of the vertebrae farther caudad. 



