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 238 A N A 1 O M Y. Part IV. the dura mater, and in feveral places with the external bronchiales, accompanying the ramifications of the bronjugular veins. ' chial artery. The vertebral veins pafs through the holes in the tranf- Afterwards the azygos detaches from the extremity verfe apophyfes of the vertebrse of the neck, fending of the arch a fmall trunk common to two or three fmail branches to the neck and occiput. They form the finus veins, Called intercojialss fnperiores dextne, which bring venales of thefe vertebrse, and communicate with the fi- back the blood from the firft three feries of intercoftal nufes of the dura mater. mufcles, and from the neighbouring part of the pleura. The axillary veins are continuations of the fubclaviae, Thefe intercollal veins fend branches through the infrom where thefe leave the thorax, to the axilla. They tercoftal mufcles to the ferratus fuperior pofticus, ferraproduce the mammarise interna, thoracica, fcapulares or tus major, &c. and afterwards they run along the inhumerales, and a branch to each arm, which, together terftices between the ribs, communicating with the venae with that from the external jugularis, forms the vena mammariae. cephalica. They likewife fend fmall branches backward to the Afterwards the axillary vein terminates in. the princi- vertebral mufcles and canal of the fpine, where they pal vein of the arm, called bafilica; which, together communicate with the venal circles, or finufes which with the cephalica, is diftributed by numerous ramifica- bring back the blood from the medulla fpinalis. tiqns to all parts of the arm, fore.-arm, and hand. As the azygos runs down, it fends off-the inferioy The portion of the inferior vena cava contained in the intercoftal veins on the right fide, one going to each ferpericardium is very fmall, being fcarcely the twelfth part ries of intercpftal mufcles. Thefe veins run along the of an inch on the fore-part, and not above a quarter of lower edges of- the ribs, and perforate the mufcles by an inch on the back part. From thence it immediately branches, which go to the pofterior and external part of perforates the diaphragm, to which it gives the vense the thorax. They communicate with the venae thoracicae, and moft diaphragmaticae inferiores or phrenicse. ; It paffes next behind the liver, through the great commonly with the mammaria interna ; and laftly, more finus of that vifcus, to which it furnilhes feveral branches, or lefs with each other, by perpendicular branches, near the pofterior extremities of the ribs. termed venue hepatica. In this courfe it inclines a little toward the fpina The. azygos fends off likewife the left intercoftal veins, dorfi and aorta inferior, the trunk and ramiucations of but feldom the whole number; for the fuperior veins which it afterwards .accompanies in the abdomen, all the come often from the left fubclavian. The inferior inway to the os facrum. tercoftal veins, to the number of fix or feven, come often Thus the inferior cava fends out on each fide, in the from the trunk of the azygos; and running between the fame manner with the aorta, the venae adipofse, renales, aorta and vertebrae, they fend off almoft the fame ramififpermaticae, lumbares, and facrse. Having reached to cations with the veins on the right fide, and likewife the os facrurn, it lofes the name of cava, and termina- fome to the cefophagus. ting by a bifurcation^ like that of the defcending aorta, The azygos, having reached below the laft rib, fends it forms the two vense iliacae. off a large branch, which bending outward, perforates Thefe iliac veins having given off the hypogaflricae, the mufcles of the abdomen, is ramified betv/een their with all their ramifications, to the vifcera of the pelvis, different planes, and communicates with the like ramifiand to fome other external and internal neighbouring cations of the laft or laft two intercoftal veins. parts, go out of the abdomen, under the ligamentum Fal- The peftorales internse, are fmall veins difpofed in loppii, and. there take the name ot vente cruraies. pairs toward the right and left hand, behind the fternum Each crural vein fends off numerous ramifications ^o all and parts near it, including the diaphragmaticse fuperithe lower extremity. ores, or pericardio-diaphragmaticae, mediaftinae, mamThe vena azygos or fine pari is very confiderable, and mariae internae, thymicae, pericardiae, and gutturales or arifes pofleriorly from the fuperior cava a little above the tracheales. pericardium. „ The right vena mediaftina goes out anteriorly from It is immediately afterwards bent backward over the the trunk of the fuperior cava, a link above the origin origin of the right lung, forming an arch which furrounds of the azygos; the left comes from the fubclavia. the great pulmonary veffels on that fide. The right fuperior diaphragmatica, or pericardio-diaFrom thence it runs down on the right fide of the phragmatica, comes anteriorly from the root of the bivertebrse dorfi on one fide of the aorta, and before the furcation near the mediaftina; and is diftributed, by feintercoftal arteries ; and getting behind the diaphragm, veral branches, to the upper, fore, and back parts of it terminates by a very fenfible anaftomofis, fometimes the pericardium, communicating with thofe of the left with the vena renalis, fometimes with a neighbouring diaphragmatica. The left fuperior diaphragmatica comes lumbar vein, and fometimes immediately with the trunk, from the left fubclavian, a little below the origin of the of the cava inferior. mammaria. The vena azygos fends out two or three fmall veins right internal mammaria arifes anteriorly from from the top of the arch, one of. which goes to the theThe a little below the angle of the birfurcaafpera arteria; the others partly to the afpera artera, tion.venaIt cava, runs along the neareft internal or pofterior edge and partly to the bronchia, by the name of vena; of the fternum, and on the cartilaginous extremities theof