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 229 Part III. A N A T O M Y. The thymus receives likewife fome rami from the mam- ramifications to the back-part of the medulla oblongata, and to the corpora olivaria and pyramidalia, which are maria interna, and intercoftaiis fuperior. The pericardia arifes much in the fame manner with likewife fpread on the back fides of the fourth ventricle the thymica, and runs down upon the pericardium, all of the brain, and form the plexus choroides of the cethe way to the diaphragm, to which it fends fome fmall rebellum. Afterwards it advances on the apophyfis bafilaris of th^ ramifications. The medialtina arifes fometimes immediately after the os occipitis, inclining, by fmall degrees, toward the verthymica, and is diftributed principally to the media- tebral artery of the other fide, all the way to the extremity of that apophyfis, where they both join in one conir jftinum. The trachealis, which may likewife be named guttu- mon trunk. rails inferior, runs up from the fubclavia, in a winding The arteria bafilaris runs forward under the great courfe, along the afpera arteria, to the glandulae thyroi- tranfverfe protuberance of the medulla oblongata, to dasas and larynx, detaching fmall arteries to both fides, which it gives ramifications, as well as to the neighbouring parts of the medulla. one of which runs to the upper part of the fcapula. The internal mammary artery comes from the anterior The fpinal arteries are two in number, one anterior, and lower fide £>f the fubclavia, near the middle of- the and one pofterior; both produced by both vertebrates, clavicula, and runs down, for about a finger’s breadth, each of which, as foon as it enters the cranium, fends behind the cartilages of the true ribs, an inch diftant out a fmall branch, by the union of which the pofterior from the fternum. fpinalis is formed. Afterwards the vertebrales advancing In its paflage, it fends rami to the thymus, medialli- on the apophyfis bafilaris, or production of the occipital num, pericardium, pleura, and intercoftal mufcles. It bone, detach backward two other fmall branches, which likewife detaches other branches through the{e mufcles, likewife meet, and, by their union, form the fpinalis anand between the cartilages ©f the ribs, to the pedloralis terior. Thefe fpinal arteries run. down on the fore and major, and other neighbouring mufcular portions ; to the back fides of the medulla fpinalis, and, by fmall tranfr mammse, membrana adipofa, and Ikin. verfe ramifications, communicate with thofe which the Afterwards it goes out at the thorax, on one fide of intercoftal and lumbar arteries fend to the fame part. the appendix enfiformis, and is loft in the mufculus ab- The internal auditory artery goes off from each fide of dominis redtus, a little below its upper part. the arteria bafilaris, to the organ of hearing, accompaThe cervical artery arifes from the upper fide' of the nying the auditory nerve, having firft furnilhed feveral fubclavian, and is prefently afterward divided into two, fmall twigs to the membrana arachnoides. which come out, fometimes feparately, fometimes by a The pofterior meningasa arifes from the fame trunk fmall common trunk. The largeft of thefe two arteries with the auditoria interna, and goes to the back-part of is anterior, the other pofterior. the dura mater, on the occipital and temporal bones, and The anterior cervicalis, running behind the carotid of fupplies the neighbouring lobes of the brain. the fame fide, is diftributed to the mufculus coraco-hyoi- When the fuperior intercoftal artery does not go ou$ dseus, maftoidasus, cutaneus, fte'rno-hyoidaeus, and fter- from the trunk of the aorta deicendens, it commonly ano-thyroidasus ; to the jugular glands, the afpera ar- rifes from the lower fide of the fubclavian, and runs down teria, the mufcles of the pharynx, bronchia, cefopha- on the infide of the two, three, or four uppermoft true gus; and to the anterior mufcles which move the neck ribs, near their heads, and fends off, under each rib, a and head. branch, which runs along the lower edge, and fupplies the The pofterior cervicalis arifes fometimes a little after intercoftal mufcles and neighbouring parts of the pleura, the vertebralis, and fometimes from that artery. It paf- Thefe branches, or particular intercoftal arteries, comfes under the tranfverfe apophyfis of the laft vertebra of municate with each other at different diftances by fmall the neck, and fometimes through a particular hole in that rami, which run upward and downward from one to the apophyfis ; and from thence runs up backward in a wind- other, on the intercoftal mufcles. ing courfe, on the vertebral mufcles of the neck, and The du£tus arteriofus, which is found only in the foethen returns in the fame manned. tus and in very young children, arifes from the aorta deThe vertebral artery goes' out from the pofterior and fcendens, immediately below the left fubclavian artery. tipper fide of the fubclavian, almoft oppcfite to the mam- In adults, this dudt is fhrunk up and clofed, and appears maria interna and cervicalis. It runs up through all the only like a fhort ligament adhering by one end to the aholes in the tranfverfe apophyfes of the vertebras of the orta, and by the other to the pulmonary artery, fo that neck, >nd, in its pafiage, fends off little twigs, through in reality it defervesno other name than that of ligamenthe lateral notches of thefe vertebrae, to the medulla fpi- tum arteriofum. nalis and its coverings. It alfo gives arteries to the ver- The bronchial arteries go fometimes from the fore-fide tebral mufcles, and to other mufcles near them. defeending aorta, fometimes from the firft It fends off a fmall branch, which is ramified on the of the fuperior and fometirnes from the arteria oefophagaea. outer and pofterior parts of the occiput, and communi- intercoftal, Sometimes they an feparately from each fide, to go tq cates with the cervical and occipital arteries. Having aflung, and fometimes by a fmall common trunk, terwards reached the great foramen of the os occipitis, each which afterwards feparale.s towards the right and left it enters the cranium, and pierces the dura mater. at the bifurcation of the afpera arteria, and ac: As foon as it enters the cranium, it fends feveral fmall hand, company the ramifications of the bronchia. Vol. I. No. 10. 3 3M The