330 VEINS OF THE DIPLOE. 



bone, and the veins corresponding with the branches of the facial 

 artery. 



The Internal maxillary vein receives the branches from the 

 zygomatic and pterygoid fossse ; these are so numerous and com- 

 municate 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 constitutes the temporo-maxillary vein. 



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

 plexiform network which is continuous with the frontal, the tem- 

 poral, auricular, and occipital veins. The ramifications of this 

 plexus form an anterior and a posterior branch which unite imme- 

 diately 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 con- 

 dyle 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 external 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 serous 

 membrane of the veins into the osseous canals in which they are 

 lodged. At the middle period of life these sinuses are confined to 

 the particular bones ; but in old age, after the ossification of the 

 sutures, they may be traced from one bone to the next. They receive 

 their blood from the capillaries supplying the cellular structure of 

 the diplae, and terminate externally in the veins of the pericranium, 

 and internally in the veins and sinuses of the dura mater. These 



