B I R 



B I R 



ing fome blood to the mufcles of the neck, make* a turn 

 backwards, enters the foramen in the tranfverfe procefs of 

 the fecond vertebra, and terminates by a Cngular anaftomo- 

 fis in the vertebral artery. 



The next branch is analogous to the internal carotid; it 

 goes forward alfo under the os hyoides, ar.d paffes behind 

 the mufcles of the jaws clofe upon the lower part of the f!<u!l, 

 at which place it fends a branch upwards, which appears to 

 penetrate the bones on the outlide of the ear, and fupply the 

 organ of hearing, fend a branch into the fkull, and another 

 through the articulation of the jaw, to unite with the oph- 

 thalmic, and contribute to the plexus at the back of the 

 orbit. The internal carotid then enters an ofTeous canal, 

 which runs along the bpfis of the cranium, between the ta- 

 bles of the bone, and at the lower and back part of the or- 

 bit, the artery receives a remarkable anallomofing branch of 

 the internal maxillary, which almoft equals in fize the caro- 

 tid itfelf ; and thefc two veflsls produce by their union, one, 

 \>'hich palTcs almoft dir^c"lly into the cranium at the ufual 

 place for the entrance of the carotid artery. This vefltl 

 lorms within the flcuU an anallomofis fimilar to the circle of 

 Willis ; but tiie branch which occupies the place of the ba- 

 Jflary artery, is very fmall, and appears to be furnifhed en- 

 tirely from the anaflomofis of the carotids, and defigned 

 only to fupply the mcdiilla oblongata arid fpinsl marrow. 

 The branches of the internal carotid are thickly fpread 

 in an arborefcent form upon the furfaces of the brain ; lome 

 on the outQdc, and others on the internal fuperficies of the 

 ventricles, and the fifTnc between the two hemifpheres. 

 The carotid alfo, as ufuai, frnds off the ophthalmic artery, 

 which, befides fupplying the eye and the parts in the 

 orbit, produces feveral ii^ofculations with the branches of 

 the externa! carotid, which will be noticed hereafter. After 

 the trunk of the carotid has parted with the two branches 

 juft defcribed, it palTes for a little way downwards and 

 forwards behind the angle of the jaw, and divides at once 

 into different branches, correfponding to thofe of the ex- 

 ternal carotid in mammalia, the firll of which mi^ht be 

 called the afophageal or laryngeal artery. This veffel fends 

 a branch to the mufcles upon the horn of theos hyoides, and 

 then turns downwards and divides into two branches, one 

 to the trachea, and the other to the csfopliagus, upon the 

 fide of which parts they dtfcend to near the thorax, where 

 they inofculate with the tracheal and ociophageal branches 

 of the common trunk of the carotid and vertebral arteries. 



The external maxillary artery dips in between the ptery- 

 goid mufcle, and that which is Ctuated at the back of the 

 lower jaw for opening the mouth ; it then palTes behind 

 the articular bone, and gives twigs upwards to the mufcles 

 of the jaws, and to the plexus at the back of the orbit : upon 

 emerging from behind the articular bone, it lies under the 

 EVgomatic procefs of the jaw, and fends an arter)' upward?, 

 which is diftributed to the tempoial and maffeter mufcles ; 

 and proceeding under tlie triangular tendon that comes 

 from the inferior margin of the orbit to the lower jaw, it 

 divides into two principal branches : one of thcfe pafits 

 along the Tide of the upper jaw", gives a branch upwards to 

 the fore part of the orbit which unites with the ophthalmic 

 artery, and is loft at the top of the head. This branch is 

 very large in birds with combs, as in conjuniflion with ihe 

 ophthalmic, it furniihes numerous vcfTels to thefe vafcular 

 parts. The artery then goes on and fupplies branches to 

 the fides of the kead before the orbits, and to the integu- 

 ments and fubftance of the upper mandible, inofculatmg 

 with the palatine branches of tne internal maxillary artery. 

 The fecond portion of the external maxillary proceeds to 

 the lower jaw, to which, and the lower part of the maffeter 



Vol. IV. 



mufcle, it is diftributed. The external raaxHlary fupplies 

 the place of the ten b'iral, labial, angular, nafal, and mtntat 

 arteries of mammalia. 



The laryngeal, or pojlerior filatine artery is a little branch 

 of the external carotid, which is fent off pofteriorly op- 

 pofite to the external maxillary artery. Its branches are 

 exhaufted upon the back part of the fauces, the mufcles for 

 moving the upper jaw, and poilerior nares. 



The Ungual, or fub-maxiUary artery pa.Tes under the mufcleS 

 which connedl the os hyoides to the lower jaw, and clofe 

 upon the back of the membrane of the lower part of the 

 mouth, it fends a branch to the ccfophagus and trachea, 

 fupplies the mufcles of the os hyoides, the tongue, the 

 lower furface of the mouth, and furnifhes the artery which 

 enters the fubftance of the lower jaw. 



Juft at the origin of the fub-maxiUary arterj-, there is 

 another httle branch of the carotid, which is loft upon the 

 mufcles of the os hyoides. 



The internal maxillary arter)' is, as ufual, the continuation 

 of the trunk of the external carotid ; it runs forwards be- 

 tween the pterygoid mufcle, and the hning of the mouth, 

 upon the fide of the long mufcle for moving the upper jaw, 

 and divides into two principal branches ; one of them 

 proceeds under the tendon of the long mufcle to get upon 

 the palate, where it forms two branches, of which one 

 runs along the external iide of the palate, between t!ie mem- 

 brane and the bone of the m.andible to the extremity of the 

 bill, where it becomes united to the fame branch r,f the op- 

 polite fide, as alfo to the rr.iddle artery of the pilate. The 

 other branch lies alio fuperficially under the membrane which 

 lines the mouth. It paffes onwards to meet its correfponding 

 veiTel of the oppofite fide with which it becomes aftually in- 

 corporated, and by their union a Cngle artery is generated, 

 which runs along the middle line of the palate to the end of 

 the mandible, where it unites with the lateral branches as al- 

 ready mentioned. At the junclion of the vefTel of each fide 

 to form the middle paktine arterv-, two branches go off, 

 which are loft upon the lining of the mouth, and the interior 

 of the organ of f.rell. 



The other branch of the internal maxillary artery is re- 

 flefted upwards towards the orbit, below which it divides 

 and unites aijain forming a triangle, through which the vein 

 pafies ; at this place it produces a remarkable plexus of 

 vefftls, like the rete mirabile of the carotid artery of qua- 

 drupeds, which is increafed by branches from the ophthalmit: 

 and the palatine arteries, and from which the back part of the 

 organ of fmell receives its fupply of blood. 



The internal maxillary artery then run^direftly "backward* 

 below the orbit, paffts between the radiated or fan-fl.up^d 

 mufcle which moves the upper jaw, and the pterviroid pro- 

 cefs ; and turning inwards round the bafis of the cranium 

 becomes incorporated with the /Wr/W carotid artery juft as it 

 enters the bonev canal, which condutts it to the brain. 



The "vertebral artery, foon after it parts from the carotid, 

 fends off a branch backwaids, which pafl'cs over the neck of 

 the fcapula and is loft among the mufcles on the poftcrior 

 part of the fhoulder, inofcu'ating with the articular and 

 other arteries about the joint ; this branch might be called 

 the fiipra-fcaj ular. In the duck we have obfervcd it before 

 it makes the turn over the fcapula to fend an artery upward* 

 alon^ the mufcles of the neck. 



The trunk of the vertebral artery proceeds obliquely up» 

 wards, and having entered the foramen in the tranfverfe pro- 

 cefs of the fecond cervical vertebra, gjives off a large branch 

 downwards, which is diftributed between the vertebra?, and 

 to the fpinal canal in the manner of the intercoftal arteries, 

 with which it anaftoiiiofcs upon arriving in the thorax. 

 3G The 



