THE SINUSES OF THE DURA MATER 



687 



glossus, and another in the genio-hyoideus. The vein is at first covered by the 

 mylo-hyoideus, perforates that muscle, runs bade along the omo-hyoideus in rela- 

 tion to the mandibular lymph glands, and joins the external maxillary near the 

 posterior border of the jaw. 



The sublingual vein (V. sublingualis) is smaller than the preceding. It re- 

 ceives veins from the skin and muscles of the mandibular space, the sublingual 

 gland, and the gums. It opens into the external maxillary vein near the lingual or 

 joins the latter. 



7. The thyroid vein (V. thyreoidea) is a large vessel which joins the jugular 

 near the external maxillary vein. It receives anterior thyroid, laryngeal, and 

 pharyngeal radicles, and sometimes a posterior thyroid vein. 



8. Muscular, tracheal, oesophageal, and parotid veins. 



9. The cephalic vein (V. cephaHca) enters the jugular near its termination. 

 It will be described with the veins of the thoracic limb. 



10. The inferior cervical vein (V. cervicalis ascendens) accompanies the as- 

 cending branch of the artery. It may open into the brachial vein. 



The Sinuses of the Dura Mater 

 These (Sinus durse matris) are blood-spaces between the meningeal and peri- 

 osteal layers of the dura mater and are lined with endothelium. In many places 



Fig. 588. — Median Section of Head of Horse, Upper Paht with Septum Nasi Removed. 

 a, Lateral mass of ethmoid bone; b, dorsal turbinate; c, ventral turbinate; d, d', turbinate folds; e, frontal sinus; 

 /, falx cerebri; g, tentorium cerebelli; h, medial surface of hemisphere: i, cerebellum; k, occipital bone; k\ occipital 

 condyle; k", paramastoid process; I, external acoustic meatus; m, temporal condyle: n, temporal canal; 1, branches 

 of ethmoidal artery; ^, ^', branches of sphenopalatine artery; S, 3', branches of sphenopalatine vein; 4^ branches of 

 ethmoidal nerve; 5, 5', branches of sphenopalatine nerve; (?, artery of corpus callosum; 7, dorsal longitudinal sinus; 5, 

 straight sinus; 9, vena magna cerebri; 10, ventral longitudinal sinus; 11> 11' , transverse sinuses; 12, dorsal petrosal sinus; 

 IS, occipital sinus; 1^, dorsal cerebral vein; 15, corpus callosum; 16, fornix. (After EUenberger, in Leisering's Atlas.) 



the lumen is crossed by fibrous strands. They receive the cerebral veins (Vv. 

 cerebri), meningeal veins (Vv. meningeae), diploic veins (Vv. diploicse), and com- 

 municate with veins outside of the cranium; their connections with the latter 

 are by means of emissary veins (Emissaria). They convey the blood directly or 

 indirectly to the jugular veins. Some are paired, others unpaired. They maj' be 

 divided into dorsal and basilar systems. 



The dorsal system comprises the following: 



The dorsal longitudinal or sagittal sinus (S. sagittalis dorsalis) is situated in 

 the convex border of the falx cerebri along the internal parietal crest. It begins 

 at the crista galli and ends near the tentorium osseum at the confluence of the 

 sinuses (Confiuens sinuum) formed by the junction with the straight sinus. It 

 receives most of the ascending cerebral veins. Along each side are small pouches 

 (Lacunge laterales) into which the veins open. The lumen of the sinus is very 

 irregular; it is traversed by fibrous bands and is partially divided by a longitu- 

 dinal septum. ' 



