THE VEINS OF THE DIPLOE. 



525 



ciliary veins with some branches from the muscles, and passes backwards near the 

 floor of the orbit to open also into the cavernous sinus, either separately or, more 

 frequently, in common with the superior ophthalmic vein. It sends a communicat- 

 ing branch downwards through the spheno-maxillary fissure to the pterygoid plexus, 

 and sometimes this offset forms the chief or sole termination of the vein. 



(M. Gurwitsch, " Ueber die Anastomosen zwischen den Gesichts- und Orbitalvenen," Arch, 

 f. Ophthalmol., xxix, 1883 ; A. F. Festal, " Recherches anatomiques sur les veines de 1'orbite," 

 &c., These, Paris, 1887.) 



VEINS OP THE DIPLOE. 



The veins of the diploe of the cranial bones are only to be seen after the pericranium is 

 detached, and the external table of the skull carefully removed by means of a file. Lodged in 

 canals hollowed in the substance of the bones, their branches form an irregular network. 



Fig. 406. SKETCH OF THE OPHTHALMIC VEINS, SHOWING THEIR DISTRIBUTION AND COMMUNICATIONS 

 WITH OTHER VEINS (altered from Hirschf eld and Leveille). (Allen Thomson.) 



The orbit is opened from the outer side and the dissection is similar to that for displaying the 

 ophthalmic artery (fig. 345, p. 410) : a, optic nerve ; b, superior oblique muscle, divided a little way 

 behind its pulley ; c, lachrymal gland lying upon the eyeball ; d, inferior oblique muscle ; e, foramen 

 rotundum ; /, maxillary antrum, opened externally : I, cavernous sinus, being joined by the common 

 trunk of the ophthalmic veins ; 1, supraorbital vein, joining the angular below and communicating 

 behind (in this case by a long branch) with the superior ophthalmic vein ; 2, inferior ophthalmic vein ; 

 3, posterior ciliary veins ; 4, 4, anterior and posterior ethnioidal branches, joining the superior oph- 

 thalmic vein ; 5, frontal vein ; 6, in front of the antrum, infraorbital vein ; 6, in the oi'bit, communi- 

 cation of the inferior ophthalmic vein with the pterygoid plexus ; II, facial vein ; 7, deep facial from 

 the pterygoid plexus ; 8, 8, 8, nasal branches ; 9, 10, angular vein ; III, temporo-maxillary trunk, 

 formed by the union of IV, the temporal and V, the internal maxillary veins ; 11, meningeal branch ; 

 12, inferior dental ; 13, 14, muscular, alveolar and communicating branches ; 15, placed in the spheno- 

 maxillary fossa above the spheno- palatine vein ; only a few branches of the pterygoid plexus are 

 represented. 



from which a few larger vessels issue. These are directed downwards at different parts of the 

 cranium, and terminate, partly in the veins on the outer surface of the bones, and partly in 

 the sinuses of the interior of the skull. They are very variable in their arrangement. 

 According to Breschet there are four such veins in each half of the cranium, viz., a frontal, 

 two temporal, and an occipital. 



The frontal is small, and issues by an aperture at the supraorbital notch to join the supra- 

 orbital vein. There is often only one frontal vein present. 



