HEAD AND NECK OF THE HORSE 



135 



connected with the basilar plexus in the cranium, and into them drain 

 vessels from the spinal cord and its meninges and from the bodies of the 

 vertebrae. 



The dorsal longitudinal ligament (ligamentum longitudinale 

 dorsale) is continuous throughout most of the vertebral canal. Its 

 commencement at the dens of the epistropheus can now be determined. 



Hyoid bone 



M. juguloh}"oideus. 



Chorda tympani 



A. maxillaris externa 



A. carotis externa. _-' 



M. digastricus (posterior 



belly). 

 M. jugulomandibularis 



M. pterygoideus internus. 



N. mandibularis. 



A. maxillaris interna. 



M. pterygoideus externus 



N. pterygoideus. 

 A. pterygoidea. 



Fig. 58. — Medial aspect of the left pterygoid region. 

 In the horse the markedly divergent alar ligaments (ligamenta 

 alaria) of the dog, cat and pig are represented by a single short and 

 strong band of slightly divergent fibres, stretching from the dorsal 

 surface of the dens to the interior of the atlas immediately cranial to 

 the fossa dentis. 



Dissection. — Disarticulate the cervical vertebrae from the skull. 



The present is a favourable time for e.xamining the pterygoid muscles 

 and their associated structures on that side of the head upon which the 

 mandible is still intact. The inferior alveolar nerve and blood-vessels and 

 tlie mylo-hyoid nerve should be revised. 



