B I R 



B I R 



the fame nerves in quadrupeds. They are diflributed to the 

 bill, and are therefore the nerves of the organ of touch in 

 birds, under which head they will be farther noticed. 



The port'io dura of the feventh pair, or the facial nerve, is 

 fo fmali in birds, that it can hardly be difcovered. Its of- 

 fices are not required, in confequence of the ftrudture of the 

 parts of the face in thefe animals. 



The poi do mollis is remarkably foft ; when it arifes from 

 the brain, it is a tender pulp, of a reddifh colour. 



The par vaj^um, or pneumo-gaflric nerve of the eighth pair, 

 fometimes paffes out of the cranium in two or three fila- 

 ments, which afterwards rejoin. On leaving the fl<ull, this 

 nerve communicates with the Ungual and glofTo-pharyngeal 

 nerves. The par vagum, after this, paffts as a dillmdt 

 ftrong cord along the neck, in company with the jugular 

 vein, and defcending into the cheft, forms the cardiac and 

 puhnoiiary plexiifcs, as in mammalia. The two nerves unite 

 behind the heart, and proceed along the cefophagus, to 

 terminate in anadomofes with the great fyiiipathctic nerve. 

 AVe have not obfervcd the recurrent branch of the eighth 

 pair. 



The gioffo-pharyngeal nen-e of the eighth pair makes its 

 exit from the cranium through the pofterior foramen lace- 

 rum in two filaments, which immediately unite to form a 

 quadrangular ganglion, which fends off a fmall nerve to the 

 anterior mufcles of the neck, and another branch to anafto- 

 mofe with the par vagum ; the nerve then defcends along 

 the ocfophagus, and divides into two branches, of which one 

 pafTcs upwards to the muftles of the os hyoides, which in- 

 clude it between th^m, and the other furnifhes a branch to 

 the hngual nerve, and afterwards is expanded upon the osfo- 

 phagus. 



The hypoghjfal nn-vc is fmall where it partes through the 

 condyloid foramen of the cranium ; it crofTes and partly unites 

 with the par vagum, at which place it detaches a filament 

 towards the thorax, which feems analogous to the defcendens 

 noni. The trunk of the hypogloffus goes forwards under 

 the horn of the os hyoides, and divides into two principal 

 branches, which are diflributed to the tongue. 



The cervical, dorfal, lumhar, and_/arr<3/ nerves, arlfe from 

 the medulla ipinalis exadtly as they do in quadrupeds, and 

 only vary in their number, which is determined by the num- 

 ber of vertebras belonging to each region of the fpine. 



The phrenic nerve is not found in birds, in confequence of 

 the abfence of the diaphragm. 



The intercofal, or great fympathetic iierre, is dcfcribed as 

 entering the cranium by the foramen lacerum pofterius. It 

 unites with the fifth and fixth pairs, and produces a lenticu- 

 lar ganglion below the fl'Cull, which communicates with the 

 eighth and ninth pair of nerves. The appearance of the 

 fympathetic nerve is, however, foon loft on the neck ; for 

 the cervical nerves form their anadomofes with each other in 

 the vertebral canal, froin which a nerve is fent out between 

 each vertebra to fiipply the mufcles and integuments of the 

 neck. Thefe nerves are remarkably large. On coming 

 into the thorax the great fympathetic fends a branch to the 

 pulmonary plexus of the par vagum ; it anaftomofcs alfo 

 with the brachial plexus ; and below the fecond rib, the 

 fympathetic commences a ferics of ganglia, which are very 

 confpicuous between each of the fncceeding ribs, but be- 

 come lefs vifible along the remaining part of the fpine. 

 Thefe ganglia are central points for the union of a number 

 of nerves. They receive filaments from each other, which 

 pafs over the heads of the ribs ; they communicate back- 

 wards with the fpinal nerves ; they detach on the ontllde 

 the intercoftal nerves, which are large, and befides fupply- 

 idg the intercollal fpaces, give branches to the mufclei and 



Vol. IV. 



integuments upon the fides of the body j they laftly fend off 

 filaments anteriorly, which anaftomofe with each other on 

 the fide of the dorfal fpine, and form cords, which becom.e 

 the fplanchnic nerves. In this manner there is produced 

 on each fide of the dorfal fpme a reticulation of nerves 

 which inclofes in its niefhes the heads of the ribs, and 

 has a ftriking effeft. The firft dorfal ganglion unites 

 with the brachial plexus and the cardiac plexus of the par 

 vagum. 



The fplanchnic nervts, after being formed by the anterior 

 branches of the fympathetic, pafs to the roots of the princi- 

 pal arteries of the vifcera. Thofe of the celiac artery pro- 

 duce a plexus round the trunk of this veflel, and where the 

 artery is divided, there are one, two, or three enlargements, 

 which are ana'ogous to tht femiiunar ganglia ; and the nerves 

 which depart from thefe, inclofe the arteries in a reticulated 

 manner, and reprefc-nt ihe foJar plexus. 



There are fimilar plexnfes on the other chief arteries of 

 the trunk, which correfpoud to the fuperior and inferi'^r me- 

 fenteric and »-f««/ plexufes, &c. 



The nerves of the fo'ar plexus accompany the branches of 

 the C!cliac artery to the tbmach, fpleen, liver, and pancreas, 

 around which they contmue to form numerous anallomofe?, 

 that uiay be compared to the fiomachic, fplenic, hepatic, and 

 pancreatic plexnfes. 



The nerves of the tuing more nearly refemble thofe of the 

 fuperior extremity in mammalia, than Cuvie-r has reprefented. 

 The brachial plexus is produced by the two lall cervical and 

 firft dorfal, and not, as he has ftaled, by the laft cervical 

 and two firft dorfal nerves. The union of thefe three 

 branches givts rife to three others, which are diftributcd in 

 the following manner : — The fiift is a very fir.e filament, 

 which runs down on the infide of the arm, and is loft about 

 the internal part of the elbow. This is analogous to the 

 internal cutaneous nerve. The feccnd is a large cord ; it gives 

 off a very large branch, which divides ii.to many others, 

 for the fupply of the pefloral mufcles ; it fends feveral 

 fmaller branches to the mufcles under the clavicle, and about 

 the joint, and then proceeds to the inner edge of the biceps 

 mufcle, along which it deicends to the fold of the arm, alter 

 giving fome large mufcular branchts. Before it reaches the 

 joint, it divides into two branches : one of which is analo- 

 gous to the ulnar nerve, and the other foon divides again 

 into nerves which are fimilar to the median and mufulo-cuta- 

 veous. The median dips down amongft the mulcles on the 

 middle of the fore arir, to which it gives branches, and af- 

 terwards runs along the interoffeous fpace, paffes under the 

 annular ligament of the carpus, and is diftributed to the ihort 

 mufcles of the digiti. The branch analogous to the mufeulo- 

 cutaneous nerve, is expanded upon the mulcles on the upper 

 edge of the radius. 



The ulnar nerve, although it appears to be incorporated 

 with the median on the upper arm, can be eafily fepa- 

 rated from it and traced to its proper origin in the brachial 

 plexus. After this nerve leaves the median, it turns over 

 the end of the foramen to get upon the edge of the uln?. 

 It gives filaments to th.e mulcles in this fituation ; but its 

 chief branch runs down fuperficially upon the ligaments of 

 the quills in company with the vein, and goes ultimately to 

 be loft upon the ulnar edge of the hand. 



The third cord furniflied by the brachial plexus, fupplies 

 the place of the radial ntrve. It detaches feveral filaments 

 to the mufcles on the infide and back of the fcapula. It 

 gives off alfo the articular nerve, and then winds round the 

 humerus between the extenfor mulcles, to which it fnrnilhes 

 fome large filaments. On coming to the outfide of the hu- 

 merus, it fends a branch between the integnaicits of the 

 3 K fold 



