VEIN. 



which are concerned only in the minor circulation : and 

 3dly, the fyllem of the vena portanim, in which the blood 

 that has circulated tlirough the organs of digeilion is con- 

 veyed to the liver, and diftributed through the fubilance 

 of that organ. The umbilical venous fyllem of the foetus, 

 with its ramifications in the placenta, its trunk in the um- 

 bihcal chord, and its fubfequent courfe and diltribution in 

 the liver, is not included under either of thefe divifions. It 

 belongs to the fetal flate of exiftence, and is defcribed under 



EiMBUYO. 



On the fubjeft of the pulmonary veins, we have nothing 

 to add here to what is ftated in the articles Lung, Circu- 

 lation, and Heart : the vena portarum is defcribed under 

 Liver ; and the pecuharities of arrangement, belonging- to 

 the veins of any organs, are noticed in the account of thofe 

 organs : fo that the prefent article will include fimply a de- 

 fcription of the fituation and courfe of the veins of the ge- 

 neral fyftem. Thefe we fhall trace, according to the courfe 

 of the blood in them, from the branches to the trunks ; as, 

 on the fame principle, the arteries have been traced from the 

 trunks to the branches. 



The veins of the general fyftem may be arranged in three 

 divifions, according to the great trunks which terminate in 

 the right auricle ; viz. the cardiac veins, thofe belonging to 

 the fuperior, and thofe to the inferior vena cava. 



L The veins of the heart do not all end in one trunk : be^ 

 fides one large vein, there are fome fmaller. The great co- 

 ronary vein of the heart ( grande veine cardiaque pollerieure) 

 runs in the groove between the left auricle and ventricle ; 

 and opens on the left of, and below the fofla ovalis and val- 

 vula Eullachii, in the right auricle. A middle coronary 

 vein runs on the inferior flat furface of the heart, between 

 the two ventricles, to open by a common orifice with the 

 former, or clofe to it. At this opening into the auricle, a 

 valve is placed, differing confiderably in fize and appear- 

 ance ; fometimes femilunar and broad, covering the whole 

 aperture, at other times fmaller and hardly diftinguilhable ; 

 fometimes perforated or reticulated. See Heart. 



Some fmaller veins open by one or more trunks in the an- 

 terior part of the right auricle. See the plates of Senac, 

 fur la Strudure du Cocur, &c. on thefe veins. 



n. The fuperior -vena cava receives the veins of the head, 

 neck, thorax, -md upper extremities. 



The fuperficial veins of the head and face end for the 

 moft part in two trunks, an anterior and a pofterior. 



The anterior facial vein (frontal or angular) commences 

 on the forehead, runs along the inner angle of the eye, and 

 then purfues its courfe obliquely along the face from the 

 corner of the eye to the bafis of the jawbone, which it pafles 

 at the fame ponit with the external maxillary artery. It 

 joins, behind the angle of the jaw, the trunk of the poilerior 

 vein. This anterior facial vein, which is a large and very 

 conftant trunk, receives a vaft number of venous ramifica- 

 tions from all parts of the forehead and face, which are covered 

 by one univerfal venous net-work or plexus. (See two ex- 

 cellent plates by Walter, Obfervat. Anat. 1775.) The fol- 

 lowing are enumerated as the veflels which open into it : 

 I, vena frontales ; 2, v. fupra orbitahs ; 3, 4, v. dorfahs 

 nafi, fuperior and inferior ; 5, palpebrahs inferior interna ; 

 6, 7, alaris nafi, fuperior and inferior ; 8, palpebrahs in- 

 ferior externa; 9, 10, labiales fuperiores ; 1 1 , 12, two 

 from the zygomatici and levator labii fuperioris ; 13, ramus 

 profundus venx facialis internae, formed by the jundion of, 

 a. vena ophthalniica facialis, which, communicating by its 

 oppolite end with the cavernous finus, receives branches 

 from fome parts in the orbit ; b. nafalis pofterior interna ; 

 c. alveolaris fuperior ; d. veins of the buccinator, &c. ; 



14, labiahs media; ij, 16, vena labii infcrioris, fuperior and 

 inferior; 17, 18, buccalis, fuperior and inferior ; 19, 20, two, 

 three, or four venae maffetericae ; 2 1 , fubmentalis ; 22, glan- 

 dnlofa. 



The pofterior facial vein is much larger than the anterior ; 

 it arifes on the fide of the head by branches accompanying 

 the ramifications of the temporal artery, defcends in front 

 of the ear, through the parotid gland, behind the angle of 

 the jaw, and unites with the former. It receives feveral 

 deep temporal veins ; the maxillaris inferior ; feveral ptery- 

 goid veins : thefe join its deep-feated trunk. The fuperficial 

 trunk is joined by three fuperficial temporal branches ; 

 articularis anterior and pofterior ; auriculares anteriores and 

 profunda ; tranfverfalis faciei ; auricularis pofterior ; feveral 

 parotid veins. 



The common trunk, formed by the union of the anterior 

 and pofterior facial veins, behind the angle of the jaw, ter- 

 minates in the internal jugular near the point, at which the 

 common carotid divides into the external and internal 

 branches. It aUo anaftomofes with the external jugular : 

 this trunk receives the fuperior thyroid vein. 



yeiris of the Brain. — They poffefs no valves : their coats 

 are much thinner than thoie of other veins ; their capacity 

 very much exceeds that of the arteries. Their greateft and 

 moft diftinguiftiing pecuharity confifts in the circumftance, 

 that they do not accompany the arteries, either in their great 

 or fmaller branches. Their trunks are coUefted in the pia 

 mater, and run either in the interval of the convolutions, or 

 over the convexities of the latter. They pour their blood 

 into receptacles formed in the dura mater, and called finufes ; 

 and in this refpeft again they difter from all other veins. 

 The finufes are compofed, externally, of the dura mater, 

 which holds the place of the external coat of other veins ; 

 internally, of a fmooth thin membrane, correfponding to the 

 internal membrane of the veins, and continuous with it. 

 The cerebral veins open in large numbers into thefe finufes, 

 of various fizes, from that of a crow's-quill to a writing 

 quill ; and they enter, for the moft part, very obliquely, and 

 with an obhquity contrary to the diredlion of the blood in 

 the finus. 



Thefe receptacles, being formed in tlie dura mater, which 

 is attached to the bone, are fixed in their lituations. They 

 are generally of a triangular figure : tiie interior is lined by 

 a fmooth membrane, but, in many inftances, it prefents fmall 

 tranfverfe fibrous bridles going from fide to fide. They 

 receive not only all the cerebral veins, but alfo thofe of the 

 dura mater and the ophthalmic. 



There are four large finufes, of which the others appear 

 to be fubordinate dependencies ; they are the fuperior lon- 

 gitudinal, the two lateral, and the fourth finus. 



The fuperior longitudinal finus (falciformis fuperior) be- 

 gins near the crifta gaUi, where it is fmall ; it runs from 

 before backwards to the internal occipital tuberofity, along 

 the middle line of the cranium, occupying the fuperior or 

 convex edge of the falx, and increafing to the fize of the 

 little finger. A vertical feftion of it, from £de to fide, is 

 exaAly triangular ; the bafe of the triangle being upwards, 

 and correfponding to the excavation in the bone, the fides 

 of the triangle being lateral, or turned towards the hemi- 

 fpheres, inchned towards each other, and united below fo as 

 to form the apex, which is downwards. Several fibrous 

 bridles crofs its cavity, which contains a greater or fmaller 

 number of the granular bodies called glandulx Pacchioni. 

 Numerous fmall veins enter the finus from the cranium, and 

 others from the dura mater ; through the pariet.il foramina 

 it receives veins from tlie integuments : blood may be ex- 

 pieffed from thefe, when they have been lacerated by de- 

 taching 



