THE MUSCLES 93 



the septum, that is, the free edge after the skin and glands have been 

 removed, follows a peculiar course (see fig. 78). Commencing 

 from the neural spine, at the caudal end of the vertebra, it passes 

 very obliquely anterodorsally, and slightly laterally, to the level of 

 the articulation with the vertebra next in front, where it reaches 

 a point on the dorsal surface of the muscle immediately lateral to 

 the median dorsal venom glands. It now turns sharply backwards 

 at a very acute angle and passes in a postero-lateral direction to some 

 distance behind the transverse process of the vertebra to which it 

 belongs, and then curves round again so as to lie directly along the rib. 

 It is continuous with the inscriptio tendinea oithQ ventral musculature. 



The fibres of the M. dorsalis trunci run between the successive 

 myosepta in an approximately sagittal direction. The whole muscle 

 is very solid and powerful. In transverse section it is 'comma' shaped. 



A fairly well-defined differentiation of this muscle mass is dis- 

 cernible on the dorsal side of the vertebrae, where a number of 

 fibres arise from the postero-dorsal edge of the post-zygapophysis 

 of one vertebra and are inserted along the dorsal surface of the neural 

 arch of the vertebra next behind, thus filling the concavity which 

 exists in this region on either side of the neural spine. This portion 

 may be distinguished as the M. interspinalis (Nishi) (m.i.s.) (figs. 7 1 

 and 78), while that portion of the M. dorsalis trunci which passes 

 between the transverse processes of the vertebrae may be dis- 

 tinguished by the name M. intertransversarius. This latter portion 

 is distinguishable from the main mass only by the fact that it arises 

 from, and is inserted on, the bone instead of the myoseptum. 



The other region where some differentiation occurs is at the head. 

 The condition is not essentially different from that in the body 

 region, as described above, but the several portions are more easily 

 distinguishable. Arising from the dorsal side of the transverse pro- 

 cesses of the second and third vertebrae a strong muscle mass spreads 

 out laterally, and is inserted over the postero-lateral aspect of the ear 

 capsule. It extends anteriorly to immediately behind the dorsal end of 

 the squamosal, and lies lateral to the superficial portion of the M. lev. 

 mandib. ant. It is the M. intertransversarius capitis superior (Gaupp, 

 in the Frog), or M. longissimus capitis (Nishi). As in Necturus it is 

 traversed by three myosepta. 



The M. rectus capitis posterior (^isKi)^ or M. occipitalis (Funk), is 

 the mesial section of the spino-occipital musculature. It lies deep to 

 the foregoing and to the M. lev. mandib. ant., and arises from the 

 neural spine and neural arch of the first vertebra. It spreads over 

 the dorsal surface of the occipital region of the skull on to which it 



