HEAD AND NECK OF THE HORSE 143 



laris) passes to the foramen rotundum along a well-marked groove close 

 to the line of junction of the temporal Aving and the body of the sphenoid 

 bone. Like the ophthalmic, the maxillary nerve lies along the side of the 

 cavernous blood sinus, but at a lower level. The mandibular nerve (n. 

 raandibularis) immediately on leaving the semilunar ganglion, traverses 

 the foramen ovale and thus gains the exterior of the cranium. The 

 small compact motor root of the trigeminal joins the mandibular nerve, 

 and will be found underneath the sensory root and the semilunar 

 ganglion. 



The abducent nerve runs to the orbital fissure medial to the oculo- 

 motor and ophthalmic nerves. 



The exits of the remaining cerebral nerves were noted during the 

 removal of the brain, A closer inspection of them may profitably be 

 made at this time. 



The sinuses of the dura mater (Sinus durae matris). — The blood 

 sinuses of the dura mater may be conveniently arranged in two groups, a 

 dorsal and a ventral, as follows : — 



Dorsal group. 



Dorsal sagittal or longitudinal sinus (sinus sagittalis dorsalis). 



Ventral sagittal or longitudinal sinus (sinus sagittalis ventralis). 



Straight sinus (sinus rectus). 



Occipital sinuses (sinus occipitales). 



Transverse sinuses (sinus transversi). 



Dorsal petrosal sinuses (sinus petrosi dorsales). 



Ventral group. 



Cavernous sinuses (sinus cavernosi). 

 Intercavernous sinus (sinus intercavernosus). 

 Ventral petrosal sinuses (sinus petrosi ventrales). 

 Basilar plexus (plexus basilaris). 



When the falx cerebri was examined, the dorsal sagittal sinus was 



found in its attached or convex border, extending from the crista galli 



of the ethmoid to near the osseous tentorium, where it joins the straight 



sinus at the confluence of the sinuses. The lumen of the sinus is 



irregular, the wall being beset with small diverticuli {lacunm ^ laterales) 



into which the veins from the upper part of the cerebral hemisphere 



open. Irregular bands cross from one side of the sinus to the other. 



The ventral sagittal sinus is very small. It runs in the concave border 



of the falx cerebri and is joined on a level with the splenium of the 



corpus callosum by the great cerebral vein. The straight sinus is 



formed by the union of the great cerebral vein and the ventral sagittal 



sinus. Passing backwards and upwards in the falx cerebri, it unites 



with the dorsal sagittal sinus at the confluens sinuum. The right and 



left transverse sinuses lie in the grooves running on the parietal bones 



1 Lacuna [L.], a pool, a pond, a gap or void. 



