VEIN. 



taching the ikuU-cap. But the principal veins it receives 

 come from the fuperior or convex furface of the hemi- 

 fpheres. Thefe are fpread irregularly over the convexities, 

 advance from the fides towards the middle, uniting into 

 larger and larger trunks, and open in confiderable numbers 

 on each fide of the finus : they receive the veins from the 

 oppofed flat furfaces of the 'hemifpheres. The anterior 

 branches are the fmalleft ; the middle and pofterior much 

 larger. They are directed at their termination obliquely 

 from behind forwards, and fometimes pafs for half an inch, in 

 the fubftance of the coats, before they open. 



The two lateral finufes, right and left (fmus tranlverii), 

 are produced by the divilion of the fuperior longitudinal at 

 the internal occipital protuberance. They are ufually of 

 equal fize, but fometimes differ in this refpeft, the right 

 being often larger. They proceed along the internal tranf- 

 verfe ridge of the occiput, at the pofterior attachment of 

 the tentorium, as far as the commencement of the petrous 

 portion of the temporal boue, when they defcend along the 

 internal furface of the maftoid portion of that bone to the 

 foramen lacerum in bafi cranii, through which they quit the 

 IkuU, taking the name of the internal jugular veins. Thefe 

 finufes are as large as the termination of the fuperior longi- 

 tudinal ; and are generally uniform on the interna! furface. 

 The cavity is triangular, where it occupies the pofterior at- 

 tachment of the tentorium : the bafe of the triangle being 

 turned backwards, and correfponding to the flcuU, and the 

 two fides being inclined towards each other, and joining at 

 an acute angle in the tentorium. Where it lies in the maf- 

 toid portion, it confifts of a layer of membrane lining the 

 bony channel, and another paffing direftly over it. 



The lateral finus receives veins from the back of the ce- 

 rebrum and cerebellum, and fome meningeal veins ; large 

 branches from the integuments of the fl<ull through the 

 maftoid foramina, and from the mufcles of the neck through 

 the pofterior condyloid holes ; veins from the cavity of the 

 tympanum, according to Soemmerring ; the fupenor and 

 inferior petrous finufes ; and the occipital finufes. 



At the under or concave edge of the falx, there is 

 found the inferior longitudinal finus (falciformis inferior). 

 This is very fmall, juft admitting a probe, and it opens be- 

 hind into the following : it may rather be regarded as a 

 vein than a finus. 



The fourth finus (perpendicularis, torcular Herophili, 

 finus droit) is placed at the junftion of the falx and tento- 

 rium, has a triangular figure, the bafts being formed by 

 the tentorium, and the fides by two oblique layers of the 

 falx, and exhibits internally feveral prominent fibrous faf- 

 ciculi. In fize it is about equal to a goofe-quill. It re- 

 ceives in front the fmall vein called the inferior longitudinal 

 finus, and a large vein, called vena magna Galeni, which 

 brings back the blood from the choroid plexufes and inte- 

 rior of the ventricles ; it alfo receives, at its under furface, 

 the fuperior veins of the cerebellum. It opens behind into 

 the bifurcation of the fuperior longitudinal finus ; fome- 

 times having a double termination. 



The fuperior petrous finus runs along the ftiarp ridge of 

 the petrous portion, at the attachment of the tentorium, and 

 opens into the lateral, juft where that begins to defcend from- 

 the tentorium. Befides fome fmall meningeal veins, it has 

 fome from the anterior lobe of the cerebrum, and from the 

 cerebellum. 



The inferior petrous finus is larger than the preceding, 

 and runs in the junftion of the bafilary procefs of the occi- 

 pital bone ai d the petrous portion of the temporal. Its 

 anterior end joins the cavernous finus, while the pofterior 

 opens into the lateral finus, juft before it enters tke foramen 



lacerum. The right and left are united by one or more 

 tranfverle communications on the bafilary procefs. This 

 tranfverfe communication unites the two inferior petrous 

 finufes juft where tliey communicate with the cavernous : 

 it is placed at the anterior end of the bafilary procefs, is 

 broad, and is defcribed by Bichat to contain the fame 

 kind of cellular fubftance as the cavernous finus. 



The cavernous is the moft complicated in its ftrufture, 

 and altogether the moft remarkable of the cerebral finufes. 

 It occupies the fide of the fphenoid bone, reaching behind 

 to the fiffure which feparates the end of the petrous portion 

 from the fphenoid, and in front to the foramen lacerum : 

 above, to the fummits of the clinoid procefles, and below, 

 to the openings through which the nerves of the fifth pair 

 pafs. The dura mater, in this fituation, is divided into 

 two layers, one of which adheres to the bone, as in other 

 fituations, and forms the internal fide of the finus ; the 

 other, which is much thicker, forms its external fide, and 

 is part of the internal furface of the cranial cavity. In 

 this latter layer the nerves of the third, fourth, and fifth 

 pairs are placed, contained in ftieaths of the membrane. 

 The interval of the two layers is occupied by a foft kind 

 of filamentous cellular fubftance, through which the nerve 

 of the fixth pair and the internal carotid artery pafs. The 

 ophthalmic vein, returning the blood from the orbit, opens 

 into this finus, which receives alfo meningeal veins, and 

 communicates vrith the veins on the fide of the bafis cranii. 

 It opens behind into the inferior petrous finus. The 

 right and left cavernous finufes are faid to communicate 

 fometimes with each other under the pituitary gland. 



The circular finus is a fmall one occupying the fuperior 

 aperture of the fella Turcica, and defcnbing a circular 

 courfe round the edge of the pituitary gland. It commu- 

 nicates on each fide with the cavernous ; and it receives 

 veins from the dura mater and the pituitary gland. The 

 anterior or pofterior femicircle, or even the whole finus, is 

 fometimes wapting. 



Occipital Sinufes. — Thefe are very fmall ; they begin at 

 the fides of the foramen magnum, run badkwards and up- 

 wards, and open into the lateral finufes clofe to their origin. 

 Anterior occipital finufes are defcribed, commimicating with 

 the inferior petrofal and the cavernous, and opening into the 

 lateral near its exit from the head : they are not conftant. 



For reprefentations of the veins and finufes of the brain, 

 fee Haller, Icon. Anat. fafcic. I ; Vicq d'Azyr, Traite 

 d'Anat. et Phyfiol. avec des pi. color, pi. 33. 35. 36. 

 Santorini, Tab. Pofthum. 3. 



The meningeal veins, or veins of the dura mater, receiving 

 innumerable ramifications from the fubftance of the cra- 

 nium, form trunks, which accompany the arteries, and often 

 on each fide, being lodged with tliem in bony channels of 

 the llvull : thefe veins open into the finules, particularly 

 towards the bafis of the fkuU, and they are faid to com- 

 municate with the pterygoid veins. 



Veins of the Eye. — (See Walter, Epiftula Anatomica de 

 VenisOculi. ) — The vena ophthalmica cerebrahs begins about 

 the internal canthus, communicating with the ophthalmica 

 facialis, goes outwards and downwards behind the globe, 

 and ends in the cavernous finus. The following veins enter 

 it ; •viz. vena nafalis, ethmoidalis anterior, infraorbitahs, 

 ciharis interna, ciliaris fuperior, lacr)inalis, ciharis pofterio*, 

 ciliares longae, ethmoidea pofterior, centralis retinse. The 

 arrangement and diftribution of thefe veflels in the eye are 

 defcribed under Eye. 



There are free communications between the external and 

 internal veins of the head, in various fituations, which have 

 been already noticed ; viz. at the parietal, the ma:ftoid, and 



the 



