526 



THE VEINS OF THE HEAD AND NECK. 



The temporal are distinguished as anterior and posterior. The anterior is contained chiefly 

 in the frontal bone, but may extend also into the parietal ; it opens externally into a deep 

 temporal vein, through an aperture in the great wing of the sphenoid, and internally into one 

 of the meningeal veins or the spheno-parietal sinus. The posterior ramifies in the parietal 

 bone, and passes through an aperture at the lower and hinder angle of that bone, or through 

 the mastoid foramen, to the lateral sinus. 



The occipital is the largest of all, and opens either externally into the occipital vein, or 

 internally into the torcular Herophili or the lateral sinus. Its ramifications are confined 

 especially to the occipital bone. 



In the young subject these veins are very small, and they become much larger in old age. 



Fig. 407. VEINS OF THE DIPLOE OF 



THE CRANIAL BONES. (Breschet.) ^ 



The external table has been re- 

 moved from the greater part of the 

 calvaria so as to expose the diploe 

 and the veins, which have been in- 

 jected : 1, a single frontal vein ; 2, 3, 

 anterior temporal vein ; 4, posterior 

 temporal ; 5, occipital vein of the 

 diploe. 



EMISSARY VEINS. 



The emissary veins are vessels 

 which pass through apertures in 

 the wall of the cranium and estab- 

 lish communications between the 

 sinuses and the veins of the ex- 

 terior of the skull. They vary 

 much in size in different indivi- 

 duals, and some of them are not 

 always present. The following vessels may be included in this group, viz. : 



(a) The mastoid emissary is the largest and most constant of these veins ; it passes through 

 the mastoid foramen between the lateral sinus and the outermost occipital, or less frequently 

 the posterior auricular vein. 



(&) The parietal emissary, occupying the parietal foramen and connecting the superior 

 longitudinal sinus with the veins of the scalp, is usually of small size, . and is frequently 

 wanting on one or both sides. 



O) The condylar emissary is also inconstant ; it passes from the lateral sinus through the 

 posterior condylar foramen to the beginning of the vertebral vein. 



(cT) A minute occipital emissary is sometimes present, passing from the torcular Herophili, 

 through a foramen which opens on the external occipital protuberance, to one of the 

 occipital veins. 



(e) One or two considerable veins descend from the cavernous sinus through the foramen 

 ovale, as well as small ones through the fibrous tissue in the foramen lacerum, to the 

 pterygoid and pharyngeal plexuses. There is frequently another vein passing through a 

 foramen of Vesalius (p. 47). 



(/) A small carotid plexus, prolonged from the cavernous sinus, accompanies the internal 

 carotid artery in the carotid canal, and opens below into the internal jugular vein. 



(7) A venous ring surrounds the hypoglossal nerve in the anterior condylar foramen, and 

 communicates internally with the occipital sinus and intraspinal veins, externally with the 

 vertebral vein and the plexus on the front of the spine. 



VEINS OF THE UPPER LIMB. 



The reins of the upper limb are divisible into two sets, the superficial, which 

 are placed between the fascia and the skin, and the deep, which accompany the 

 arteries. The superficial veins are much larger than the deep, and take a greater 

 share in returning the blood, especially from the distal portion of the limb. Both 

 sets are provided with valves, and these are more numerous in the deep than in the 

 subcutaneous reins. Yalves are constantly present at the entrance of branches into 

 the main vessels. 



