- LIVER. 



\mion, and is called the inferior mefenteric vein. From 

 the redlunv, of which the veins are often called the hemor- 

 rhoidal, the inferior mefenteric trunk afcetids parallel to the 

 in'eftine, goes behind the tranfverfe mefocolon, and termi- 

 nates behind the pancreas, at a right angle, in the fpicnic 

 ,*Ein. This vein is very fmall at its origin, where it anaf- 

 tomofes with thofe of the hypogaftric plexus : it grows 

 larger as it afcends, and is nearly equal in diameter to the 

 fiiperior mefenteric vein at its termination. 



Thus we obferve, that there are two principal trunks 

 forming the vena portarum, and receiving nearly all the veins 

 of the organs, from which this peculiar venous fyftem de- 

 rives its origin ; thefe are the fuperior mefenteric and the 

 fplenic ; fome branches, however, direftly join the trunk. 

 The fplenic, formed in the manner already fpecified, is not 

 tortuous like the artery, runs in company with, but below 

 j', along the upper edge of the pancreas, in an horizontal 

 direction from left to right. In front of the vertebral 

 column it ends, at nearly a right angle, in the vena por- 

 tarum. In this ccurfe it receives veins from the great 

 end of the ftonach, the left inferior gailric vein, the inferior 

 mefenteric, the fuperior gaftric, and feveral pancreatic veins. 

 The fuperior mefenteric vein, in the greateil part of its 

 Courfe, accompanies the artery of the fame name, being 

 placed 'to the right, and a little in front of it. It arifes 

 where the artery ends, that is, near the csecum and the right 

 fide of the colon ; it afcends, following the fame courfe with 

 the artery, between the two layers of the mcientery, and 

 becomes larger as it receives new branches. At the pof- 

 terior edge of the mefocolon it goes behind the pancreas, 

 and joins at a fomewhat obtufe angle the fplenic vein, to 

 form the trunk of the vena portarum, or the ventral or ab- 

 dominal vena p., as it is fometimes called, to diltinguifh it 

 from that end which ramifies in tlie liver, and which is called 

 the hepatic vena p. In this fituation it is more than an inch 

 <3iftant from the end of the inferior mefenteric vein. It re- 

 ceives, on the concave fide of its curve, the three veins from 

 the right portion of the large inteftine ; on the convex or 

 left Gd" the numerous veins of the fmall inteftine. Several 

 duodenal and pancreatic veins join it where it paffes between 

 the duodenum and pancreas. 



The trunk of the vena portarum, the diameter of which 

 is much lefs than the united diameters of the two preceding 

 veins, goes obliquely upwards to the right, and a little 

 backwards, and palfes through a fpace of about four or 

 five inches in the adult, from the vertebral column to the 

 great tranfverfe fiffure of the liver. At firft it is fituated 

 behind the right extremity of the pancreas, and the fecond 

 portion of the duodenum ; it then forms a part of the faf- 

 cicul'.is of biliary veffels contained in the capfula Gliffoni 

 (fee Epiploon), where the biliary dufts and the hepatic 

 artery cover it in front. Like the lail mentioned parts, it 

 is furrounded by numerous nerves, lymphatic veflels and 

 glands ; and thefe organs are all connected by a tolerably 

 denfe atul copious cellular tifTiie. When the trunk has ar- 

 rired at the notch of the liver, it is bifurcated, and each 

 branch forms with it nearly a right angle ; fo that the two 

 taken together reprefent a horizontal canal lying in the 

 Rotch of the liver, connefted ciofcly on each fide to the 

 correfpondirig divifions of the hepatic artery, and having 

 the trunk of the vena portarum opening perpendicularly 

 into its middle. This canal, fometimes called by auatomills 

 the fi;ius of the vena portarum, does not immediately touch 

 the fubilince of the liver; a thick layer of denfe cellular 

 tiffue feparates it, and is continuous with the general ex- 

 ternal covering of the divifions of the vein in the organ. 

 The right branch, fhorter, but much larger than the left. 

 Vol. XXI. 



enters the great lobe by the corrcfponding extremity of the 

 tranfverfe notch, and divides into an uncertain number of 

 branches. The other pafies horizontally towards the left, 

 as far as the notch containing the umbilical vein, of which 

 the remaining fibrous cord is firmly attached to it, and fpliti 

 into branches diftributed through the left lobe. The pri- 

 mary and fecondary divilions generally piirfue a horizontal 

 conrfe ; they then divide into an infinite number of ramifi- 

 cations, the dillribution of which we cannot regularlv follow, 

 and which end at lalt in a capillary fy Hem extending through- 

 out the fubllance of tlie organ. Each of the ramifications, 

 which we can ealily trace in the liver, is accempani.d by 

 a branch of the hepatic artery, by one or more biliary 

 dutts, fome nervous filaments, and lymphatic veflels. Thele 

 parts are connefted and furrounded by a fine byer of cel- 

 lular tiffue, which adlicies clofely to the fubftance of ihc 

 liver, and is often defcnbed by the name of capfule of 

 Gliffon ; it feems to infulate the parts which it funounds, 

 as it fepai'ates them from the proper tiffue of the liver. It 

 has no conneftion with the peritoneum, and the fnppofitions 

 of its mufculariry and its propelling the b ood by that 

 power are fupported by no proofs whatever. Boyer re- 

 gards it as a prolongation of the proper membrane of the 

 liver, which, he lays, is reflected over all the veflels that 

 enter or quit the organ. As the parts contained in thefe 

 capfules are connefted to each other by loofe cellular tilfue, 

 which enters the liver with them, the orifices of the vena 

 portarum, on a feftion of the organ, have a loofe plaited 

 appearance, diftinguirtiing them from thofe of the hepatic 

 veins, which, as they are intimately connefted to the proper 

 tiliue of the liver, preferve their circular area, and prefcnt 

 a much cleaner cut. 



The hepatic artery is a branch of the celiac trunk, and 

 has been deicribed in the article Artery. Its branches 

 enter at the great notch, and every where accompany the 

 ramifications of the vena portarum. 



The defcription of the hepatic veins is given in the article 

 Vein*. We have to notice here only the circurallances that 

 delerve attention, concerning their dittribution in the liver. 

 They return, to the general venous fyftem, the blood which 

 is brought into the iivcr both by the hepatic artery and the 

 vena portarum. They arife, therefore, out of the capillary 

 fyftem, in which the two orders of veflels, juft named, ter- 

 minate. They unite fucceflively into larger and larger 

 branches, which form ultimately three principal and fome 

 fmaller trunks, opening into the inferior vena cava, juft 

 under the diaphragm. This proximity to the heart ac- 

 counts for their being fo often diftended with blood in the 

 dead body. Befides the direftioii, in which the blood paffes 

 through them, the hepatic veins are diftinguiflied by two 

 principal circumftances. Their fides are rather thinner than 

 thofe of the vena portarum ; and they have n« trace of the 

 cellular covering, delcnhed above, as belonging to tht 

 ramifications of the latter vedei, but adhere immediately 

 to the. tiffue of the liver, fo as to prefent a perfeftly cir 

 cular area on a lectio.). 



The nerves, which are fmall in comparifan to the bulk 

 of the organ, come chiefly from the plexvs of ca:liac gan- 

 glia ; but feveral filaments from the eigith pair join thefe. 

 See Nervi .■ 



The ly-nphatic vcfTels of the liver are very numerous, in* 

 fomuch tiiat no other organ feems to be move ahund ntly 

 fuppHed with them. They are diftingui(hed into two orders, 

 the fuperficial and the dcep.fea.ed. The former cover the 

 whole external furiace, and are eafily diftinguilhed hy ihe 

 contrail of their colour, with that of the tiffue of the liver. 

 The latter, arifing in the fiibitaiice of tiie organ, foUow 

 £b the 



