950 THE OSTEOLOGZ AND MYOLOGY OF THE DEATH ADDER, 



as being continuous with the upper set ; they are distinguished 

 from the upper set by the bundles running more antero-posteriorly. 

 They, however, appear like the superior muscles to be modified 

 intercostals. 



Mm. levatores costarum externi. 



Mm. levatores costarum, Hoflfmann ; Ri2?penlieber, D' Alton, 

 Hiibner, Meckel ; Transverso-costal, R. Jones ; Levatores hreviores, 

 Owen. 



The levatores costarum arise from the process extending upwards 

 from the diapophysis, also from the rib articulating with the 

 diapophysis. Each muscle runs backwards, and slightly down- 

 wards, to be inserted on the upper portion of the inner third of the 

 anterior surface of the rib immediately behind. The muscle can 

 act not only as an elevator to the ribs, but also as an external 

 oblique muscle. The levatores costarum are wholly hidden by the 

 sacro-lumbalis and accessorius ; these, however, being separated from 

 them by the origins of the external oblique from the lateral septum. 



Each muscle is supplied by a branch from the intercostal nerves ; 

 it emerges close to the line of insertions. 



Mm. levatores costarum interni. 



Mm. costo-vertebrales inferiores, Hoffmann ; Innere, Heine vor- 

 wdrtszieher der Rij^pen, D'Alton ; Innere Rippenheber^ Meckel ; 

 tSpinoso-costales, Hiibner. 



The levatores costarum interni arise from the base of the hypa- 

 pophyses and from the inferior surface of the centrum. They run 

 outwards, and backwards, to be inserted into the under surface of 

 the head of the rib, immediately behind. 



This is the arrangement in all the venomous snakes that we 

 have examined ; but in Morelia and other non-venomous forms the 

 levatores costarum are large muscles arising from the hypapophyses 

 and inserted into the third vertebra behind. The intercostal 

 nerve runs internal to these muscles, separating them from the 

 transverse layer. 



