VEINS OP THE DIPLOE. 369 



supra-orbital, which joins the frontal vein ; the dorsal veins of the nose 

 which terminate in the nasal arch ; the ophthalmic, which communi- 

 cates with the angular vein ; the palpebral and nasal, which open into 

 the angular vein ; a considerable trunk, the alveolar., which returns 

 the blood from the spheno-maxillary fossa, from the infra-orbital, 

 palatine, vidian, and spheno-palatine veins, and joins the facial be- 

 neath the zygomatic process of the superior maxillary bone, and the 

 veins corresponding with the branches of the facial artery. 



The Internal maxillary vein receives the branches from the zygo- 

 matic and pterygoid fossae ; these are so numerous and communicate so 

 freely as to constitute a pterygoid plexus. Passing backwards behind 

 the neck of the lower jaw, the internal maxillary joins with the 

 temporal vein, and the common trunk resulting from this union consti- 

 tutes the temporo-maxillary vein. 



The Temporal vein commences on the vertex of the head by a plexi- 

 form network which is continuous with the frontal, the temporal, 

 auricular and occipital veins. The ramifications of this plexus form 

 an anterior and a posterior branch which unite immediately above the 

 zygoma ; the trunk is here joined by another large vein, the middle 

 temporal, which collects the blood from the temporal muscle, and around 

 the outer segment of the orbit, and pierces the temporal fascia near the 

 root of the zygoma. The temporal vein then descends between the 

 meatus auditorius externus and the condyle of the lower jaw, and 

 unites with the internal maxillary vein, to form the temporo-maxillary. 



The Temporo-maxillary vein formed by the union of the temporal 

 and internal maxillary, passes downwards in the substance of the 

 parotid gland to its lower border, where it becomes the external 

 jugular vein. It receives in its course the anterior auricular, masse- 

 teric, transverse facial, and parotid veins, and near its termination is 

 joined by the posterior auricular vein. 



The Posterior auricular vein communicates with the plexus upon 

 the vertex of the head, and descends behind the ear to the temporo- 

 maxillary vein, immediately before that vessel merges in the external 

 jugular. It receives in its course the veins from the external ear and 

 the stylo-mastoid vein. 



The Occipital vein commencing posteriorly in the plexus of the vertex 

 of the head, follows the direction of the occipital artery, and passing 

 deeply beneath the muscles of the back part of the neck, terminates in 

 the internal jugular vein. This vein communicates with the lateral 

 sinus by means of a large branch which passes through the mastoid 

 foramen, the mastoid vein. 



VEINS OF THE DIPLOE. 



The diploe of the bones of the head is furnished in the adult with 

 irregular sinuses, which are formed by a continuation of the internal 

 coat of the veins into the osseous canals in which they are lodged. At 



