ART 



ART 



by its branches. They may be divided into tliree claffes. — to the pericardium ; and fomc fmall twigs to the anterior 



The pofterior or fhort ciliaiy arteries funound the optic 

 nerve ; they divide into twenty or thirty branches, which 

 perforate the back of the fclerotica, and are diftributed to 

 the choroid. The long ciliary arteries are two in number ; 

 they perforate the fclerotica at one-third of the diftance be- 

 tween the optic nerve and the cornea ; arriving at the orbi- 

 culus ciiiaris, thty divide into two branches, which follow 

 the outer circle of the iris, and communicating together, 

 form the zona major of the iris ; the branches of this form 

 the zona minor on the inner circumference of the iris. The 

 anterior ciliary arteries penetrate the front of the fclerotica, 

 and contribute to the formation of the zones of the iris. 

 Thefe ve 



mediaftinum, and back of the (lemum.~ Other branches 

 come off at the intervals between the cartilages of the ribs, 

 communicate with the intercoftal arteries, and then go out 

 to the mufcles on the outfide of the cheft. 



The inferior thyroideal aiterj- arifes from the upper part 

 of the trunk, where it is covered by the ftcrno-clcidomaltoi- 

 deusj it divides almoft immediately into four branches. 

 I. The proper thyroid branch bends in a tortuous manner 

 under the carotid arter)-, till it arrives at the thyroid gland, 

 to which it is diilributcd, communicating with the fuperior 

 thyroideal artcr)-. This branch fends one or two fmall twigs 

 down along the trachea. 2. The afcending thyroid branch 



r.ils ill the fcEtus produce the arteries of the mem- is a fmall but conllant arten-, which partes upwards in front 

 brana pupillaris. The inferior mufcular arter)- goes to the of the tranfverfe procefics of the cenical vertebrse and is 

 mufcles which are found beneath th.e globe of the eye ; diftributed to the neighbouring m.ufcles and nerves. ".The 

 viz. the obliquus minor, the reftus inferior and e.Kternus. tranfverfe artery of the neck goes alon^ the fide of the neck 

 The a.i;;rior a;thmoidal arter)' pafTts through the anterior and is diftributed to the trapezius and neighbouring rnuf- 

 orbitary hole ;_and entering the l1<ull, is diftributed to the cles of the fcapula. 4. The tranfverfe artery of the fhoulder 



(tranfverfalis fcapularis, or fcapularis fuperior) pafles 

 along the root of the neck towards the fcapula, giving oiT 

 branches to the neighbouring mufcles. The trunk paffing 

 through the notch in the fuperior qofta of the fcapula, 

 takes the name of the lupra-fcapulary arter)- ; it fends oft" 

 many branches to the fupra-fpinatus mufcle, then defccnds 

 under the acromion to the lower part of the fcapula, where 

 it communicates veiy largely and freely with the infra-fca- 

 pulary artery. 



Objlr-vc.t'wii. Sometimes the tranfverfe artery of the 



dura mater. The fuperior and inferior palpebral arteries are 

 deftined for the upper and lower eyelids. The trunk, ar- 

 riving at the inner a .gle of the eye, fplits into two branches : 

 the nafal branch croffes the lacrymal bag, dtfcends along the 

 ala nr.fi, and communicates with the labial artery. The 

 frontal branch is diftributed to the fcalp, and communicates 

 with the temporal. 



After the carotid has arrived at the anterior clinoid pro- 

 cefs, it fends oif feveral fmall branches, fome one of which 

 goes to the choroid plexus. 



Then it fends off the communicating artery, which meet- fiioulder is a branch of the fuperficial cervical artery. S 



ing and anallomofing with a fimilar branch of_ the vertebral, 

 contributes to form the celebrated circle of Willis. 



The artery then divides into an anterior and a pofterior 

 branch. 



The anterior branch, or the artery of the corpus callo- 

 fum, comes forward in the divifion between the two anterior 

 lobes of the biain. Here it approaches the artery of the 



times it comes oiF as a diftincl trunk from the axillary 

 artery, and then the name of fupra-fcapulary is applied to the 

 whole of it. In thefe cafes the fourth branch of the thy- 

 roideal is fmall, and only reaches to the furface of the tra- 

 pezius, deltoid, &c. 



The vertebral, which is an artery of great magnitude,- 

 . arifes from the upper part of the fubclavian, behind the 



oppofite fide, and has a ftiort but large communication with inferior cervical ganglion of the great fympathetic nerve : 

 it juft above the junction of the optic nerves. This commu- it afcends through the foramina of the tranfverfe proceifes 

 nication completes the circle of Willis in front. The reft of the cerifcal vertebra:, entering at the fixth, fifth, or 

 of the trunk pafTcs firft upwards, auvi then turns backward fourth vertebra. In paling from the fecond to the firft 

 over the corpus dallofum, and between the two hemifpheres vertebra, it makes a great turn ; then it again bends back- 

 of the brain. _ ' wards along that groove of the atlas which is deftined to 



The pofterior branch, or artery of the filTura fylvii, runs receive it. Entering the f!<ull at the foramen m.agnum, it 

 direclly outv/ards, and enters the fifTura Sylvii ; its branches afcends along the balilary procefs of the occiput, and uu- 

 fupply the middle part of the brain chiefly. der the medulla oblongata to meet the artery of the oppo- 



Obferva'lon. All the arteries of the brain and cerebellum fite fide at an acute angle ; by the union of the two 



ramify firft upon the pia mater, and then enter the cortical 

 fubftance of the brain. They do not follow the directions 

 of the convolutions. They are compofed of thinner coats 

 than other arteries, whence the blood may be feen even 

 through the coats of the larger arteries. 



The fubclavian artery afcends behind the head of the 

 clavicle and the infertion of the fterno-cleidomaftoideus muf- 

 cle, towards the fcaleni mufcles ; it pafics between the ante- 

 rior and middle fcalenus, and then bends over the firft rib 

 into the axilla, where it takes the name of the axillary ar 



trunks the bafilar artery is form.ed. The vertebral arterv, 

 as it paffes through the tranfverfe procefTes, gives off forae 

 branches to the fpinal marrow. While it is paffing through 

 the occipital hole, it fends off the pofterior menii:o-eal 

 artery, which fupplies the dura mater on the occiput, and 

 extends as far the fphenoid bone. The inferior arterj' of 

 the cerebellum anfes immediately before, or after the union 

 of the vertcbrals ; it comes off" near the origin of the par 

 vagum, and having diftributed feveral branches to the inferior- 

 furface of the cerebellum, teniiinates in the fourth ventricle. 



ter)'. The outer edge of the fcalenus may be confidered The anterior and pofterior fpinal arteries arc ufually given 

 as the boundary between the fubclavian and axillaiy portions off before the union of the vertcbrals. They defcend alon 



of the veffel. 



Branches of the Suhclav'tan Ailery. 

 The internal mammary artery comes off from the f-ont 

 of the fubclavian ; it paftcs behind the articulation of the 

 fternum and clavicle, tlien goes along the middle of the 

 cartilages of the ribs, and tenninates on the reftus abdomi- 

 nis by communicating with the epigaftric, intercoftal, and 

 lumbar arteries. It fends an artery to the thymus ; a fmall 

 branch which accompanies the phrenic nerve ; two arteries 



the front and the back part of the medulla fpinalis, and 

 keep up their fiae almoft to the bottom of it by means of 

 frequent communications with branches from without. Tiie 

 bafilar artery pafles along the middle of tiie tuberculum 

 annular? to its anterior margin, giving feveral fmall branches 

 to its inferior furface. Then it divides into four branches, 

 two for each fide of the brain. The fuperior arter)- of the 

 cerebellum bends round the crura cerebri, and is diftributed 

 to the upper part of the cerebellum ; it alfo gives branches 



