ANATOMY. 



sr nils oil' branches : these, again divided, 

 form ramifications: and in their further 



->s form twigs, filaments, &c. and 

 this di vision gt)es on, until the nerve, from 

 its smallness, can be no longer traced. 

 Set we can manifestly discern the nervi-s 

 in some instances, as in the organs of 



-miniating in a pulpy expansion. 

 I. ike the arteries, nerves communicate 

 with cadi other ; and it is conjectured 

 that these communications, like those, of 

 the blood-vessels, are designed to obviate 

 the effects of the injury of compression 

 of am particular nervous trunk. In some 

 parts these communications are very nu- 

 merous, so as to constitute a minute net- 

 work of nervous filaments, calledaplexus. 

 Description of tlie particular nerves. 

 There are in the whole body thirty-nine 

 pairs of nerves ; of which nine arise from 

 the brain, and thirty from the spinal mar- 

 row. There is another pair, called the 

 great sympathetic, which can hardly be 

 ascribed to cither of these ch. 



Nerves ofttte brain. 



1st. pair. Olfactory nerves; arise from 

 liie corpora striata, and go through the 

 cribriform lamella of the ethmoid bone to 

 the pituitary membrane of the nose. 



2d pair. Optic nerves ; arise from the 

 thalami nervonim opticorum,and proceed 

 to the eye-ball, where they are expanded 

 to form the retinae. 



3d pair. Nervi motores oculorum ; 

 arise from the crura cerebri, and are dis- 

 tributed to some of the muscles of the 

 eye-ball. 



4th pair. Nervi trochlcares; come from 

 tin- \alve of the brain, and supply the 

 trochlearis muscle of the eye. 



5th pair. Nervi trigemini ; arise from 

 the side of the medulla oblongata. This 

 nerve divides into three branches, of 

 \vhichthefirst, or ophthalmic, goes into 

 the orbit, and after giving a few branches 

 there passes out on the forehead. The 

 second, or superior maxillary, supplies 

 the parts about the upper jaw; a remark- 

 able branch of it is the infra-orbital, which 

 comes through the large hole under the 

 orbit to the face. The third, or inferior 

 maxillary, is distributed to the lower jaw 

 and adjacent parts. 



6th pair. Nervi motores externi ; from 

 the medulla oblongata to the external 

 s-traight muscle of the eye. 



7th pair. Nervi auditorii. Tim pair 

 consists of two nerves lying in contact, 

 but completely distinct from each other, 

 both in their origin, course, and distribu- 

 tion. The portio mollis of this nerve is 



distributed to the labyrinth of the ear. 

 The portio dura goes through the tempo- 

 ral bone, and is very widely spread over 

 the face. These nerves are me: 

 rectly termed nervus auditorius, and ner- 

 vus facialis. The chorda tympani is 

 branch of communication between the fa- 

 cial nerve and the lingual branch of the 

 inferior maxillary. 



8th pair. Par vagum ; arises from the 

 medulla spinalis, before it quits the cra- 

 nium. It receives an accessory branch, 

 that originates from the upper portion of 

 the medulla spinalis, contained in the cer- 

 vical vertebrae. The par vagum passes 

 along the neck, in company with the ca- 

 rotid artery and the internal jugular vein. 

 It sends oH' in the upper part of the neck, 

 1. the glossopharyngeal nerve ; 2. supe- 

 rior laryngeal ; and 3. the accessory 

 branch. The trunk that enters the chest, 

 and gives rise to the inferior laryngeal or 

 recurrent nerve. It afterwards becomes 

 connected to the oesophagus, and passes 

 the diaphragm in conjunction with that 

 tube, to be distributed finally to the sto- 

 mach ; sending ' in its passage several 

 branches which supply the lungs. 



9th pair. Nervi linguales ; arise near 

 the former, go through the foramen con- 

 dyloideum, and supply the muscles of the 

 tongue. 



Nerves of the medulla nfunulis. The cer- 

 vical nerves, soon after they come out 

 from between the vertebrae, communicate 

 with each other. They supply all the 

 muscles which are situated about the ver- 

 tebrae of the neck. The second sends * 

 large branch, which ramifies extensive!} 

 over the occiput. 



The nerve of the diaphragm, called the 

 phrenic or diaphragmatic, arises princi- 

 pally from the fourth cervical nerve. It 

 lies close on the anterior scalenus muscle, 

 then goes over the pericardium to the 

 diaphragm. 



The tour lower cervical nerves, and the 

 first dorsal, concur in forming the axillarv 

 plexus, from which the upper extremity 

 its supply. These are large ner- 

 vous trunks, coming out at the side of the 

 neck, and variously united to each other. 

 The\ go behind the clavicle with the axil- 

 lary artery. This plexus sends off the 

 following branches : 



1 Ni rvi thorucici, accompanying the 

 thoracic arU 



2. Nervus supra-scapularis, distributed 

 with the artery of t lie <ame name. 



3. Nervus axHlarift, following the coone 

 of the posterior circomflei Ml 



tancus internus, running over the 



