John Mar shall Williamson Hemorial QUAIN'S ELEMENTS OF ANATOMY EDITED BY EDWARD ALBERT SCHAFER, F.R.S. PROFESSOR OF PHYSIOLOGY AND HISTOLOGY IN UNIVKRSITY COLLEGE, LONDON", AND GEORGE DANCER THANE, PROFESSOR OF ANATOMY IN UNIVERSITY COLLEGE, LONDON. IN THREE VOLUMES. VOL. III.— PART II. THE NERVES. BY PROFESSOR THANE. ILLUSTRATED BY 102 ENGRAVINGS. LONDON : LONGMANS, GREEN, AND CO. AND NEW YORK. 1895. "ft | All rights \escrved. ] LONDON : IADBVRY. AGNEW. & CO. MX. PRINTER?, WHITEFRIARS. 1895" CONTENTS OF PAKT II. THE NERVES. THE CEKEBRO-SPINAL NKUVES CRANIAL NERVES Connection with Cerebro-Spinal Axis .Mode of Exit from the Cranium . General Distribution I. Olfactory Nerves . . . II. Optic Xerve ..... III. Oculomotor Xerve . . . . Position of Nerves at the Caver- nous Sinus and as they enter the Orbit . . .' . IV. Trochlear Xerve . . . . V. Trifacial Xerve .... Ophthalmic Nerve . . . . Ciliary Ganglion .... Superior Maxillary Xerve . . Spheno- Palatine Ganglion . Inferior Maxillary Xerve Submaxillary Ganglion Otic Ganglion . . . . VI. Abducent Xerve .... VII. Facial Xerve VIII. Auditory Xerve .... IX. Glosso-Pliaryiigeal Xerve . . . X. Pnemno- Gastric Xerve . XL Spinal Accessory Xerve XII. Hypoglossal Xerve SPINAL NERVES The Roots of the Spinal Xerves . Posterior Primary Divisions of the Spinal Nerves . .... Suboccipital Nerve .... Cervical Nerves ..... Dorsal Nerves ..... Lumbar Nerves Sacral Nerves ..... Coccygeal Nerve Anterior Primary Divisions of the Spinal Xerves ...... Cervical Xerves Suboccipital Xerve Second Cervical Nerve . . . Cervical Plexus .... Superficial Ascending Branches Superficial Descending Branches . Deep Branches : Internal Series . Deep Branches : External Series . Brachial Plexus ..... Branches above the Clavicle . Branches below the Clavicle . . Anterior Thoracic Nerves . Subscapular Nerves . . . Circumflex Nerve Internal Cutaneous Nerve . . PAGE 221 221 222 223 225 227 227 228 23I 231 233 235 237 238 241 243 248 248 250 269 271 274 275 278 278 280 280 281 281 283 283 283 283 284 285 286 287 287 288 289 291 294 294 294 294 295 Unpt N« SPINAL NE it VES — continued. Brachial Plexus — Small Internal Cutaneous Nerve Musculo-Cutaneous Nerve . Ulnar Nerve ..... Median Nerve .... Musculo-Spiral Nerve . Radial Nerve .... Posterior Interosseous Nerve . . Dorsal Nerves . . . . . First Dorsal Nerve .. . . . >er or Pectoral Intercostal erves ..... Lower or Abdominal Intercostal Nerves . . .... Last Dorsal Nerve Lumbar Nerves .... Lumbar Plexus .... Ilio-Hypogastric and llio-Inguinal Nerves . Genito-Crural Nerve External Cutaneous Nerve . . Obturator Nerve .... Anterior Crural Nerve Fifth Lumbar Nerve Sacral and Coccygeal Nerves Fourth Sacral Nerve Fifth Sacral Nerve .... Coccygeal Nerve .... Sacral Plexus Collateral Branches Small Muscular Branches Superior Gluteal Nerve Inferior Gluteal Nerve . Small Sciatic Nerve . Perforating Cutaneous Nerve Terminal Branches . . . . Pudic Nerve Great Sciatic Nerve . . . Internal Popliteal Nerve . Posterior Tibial Nerve . Internal Plantar Nerve External Plantar Nerve External Popliteal Neive . Musculo-Cutaneous Nerve Anterior Tibial Xerve SYNOPSIS OF THE SENSORY DISTRIBUTION OF THE CERERRO-SPINAL NERVES. Cutaneous Distribution of the Spinal Nerves to the Trunk and Limbs . Sensory Distribution of the Spinal Nerves to the Viscera . Literature of the Distribution of Sensorv Nerves PAGE 296 297 299 3OI 303 304 306 307 307 308 310 312 315 317 317 319 322 322 323 323 323 323 325 325 325 326 326 328 328 328 330 331 332 333 334 335 336 337 338 344 350 351 VI CONTENTS OF PART II. SYNOPSIS OF THE MUSCULAR DISTRIBU- TION OF THE CEREBRO-SriNAL NERVES . . . . . •. 351 Muscular Distribution of the Spinal Nerves 354 Literature of the Muscular Distribution of Spinal Nerves .... 356 SYMPATHETIC NERVES . . . . 357 Gangliated Cords . . . 358 Kami Communicautes . ... 358 Kami Efferentes 360 Pre vertebral Plexuses . . . . 361 Cervical Part of the Gangliated Cord . 361 Upper Cervical Ganglion . . . 361 Ascending Branch and Cranial Plexuses ..... 362 Pharyngeal Nerves and Plexus . . 363 Upper Cardiac Nerve . . . 363 Branches to Blood- Vessels . . 364 Middle Cervical Ganglion . . . 365 Lower Cervical Ganglion . . . 365 Thoracic Part of the Gangliated Curd . 367 Lumbar Part of the Grangliated Cord . 370 Sacral Part of the Gangliated Cord . 370 The Great Plexuses of the Sympathetic . 372 Cardiac Plexus . Solar or Epigastric Plexus . Hypogastric Plexus .... Pelvic Plexus . . . Recent Literature of the Sympathetic . MORPHOLOGY OF THE PERIPHERAL NERVES SPINAL NERVES Segmentation . Mode of Division ..... Posterior Primary Divisions Anterior Primary Divisions . . . Nerves of the Limbs. Meningeal Divisions . . . Visceral Divisions .... Ganglia . . . . . . Constitution of a Segmental Nerve . CRANIAL NERVES ..... Constitution of the Cranial Nerves . Ganglia Segmentation ..... Course and Distribution . . . Literature of the Morphology of the Peripheral Nerves INDEX PAGE 372 373 377 377 379 38i 382 384 384 384 384 385 385 387 388 390 390 393 THE NEKVES, EV G. D. THANE. IN this section is comprised the descriptive anatomy of the cerebro-spinal and sympathetic nerves, and their ganglia. Together with these the peripheral division of the nervous system also includes the organs of the external senses, which will be described in the following section. The minute structure of the nerves and their mode of ending in the several tissues and organs of the body are discussed in the sections General Anatomy and Splanchnology. The separation of the sympathetic from the cerebro-spinal nerves is convenient for purposes of description, but do^s nob indicate a difference of origin or an anatomical independence of the two systems, since the fibres composing the sympathetic are connected centrally, either -directly or indirectly, with the cerebro- spinal axis, which they leave as constituents of the roots of certain of the cerebro- spinal nerves. Moreover, the division cannot in all cases be strictly maintained, for some of the ganglia (ciliary, spheno-palatine, otic, and submaxillary), which are described in connection with the cranial nerves to which they are attached, have a close affinity with those of the sympathetic system, while on the other hand many of the terminal plexuses distributed to the viscera, and generally regarded as parts of the sympathetic system, are composed in large part of fibres which pass into them directly from cerebro-spinal nerves without traversing the cord of the sympathetic. THE CEREBRO-SPINAL NERVES. The nerves springing directly from the great cerebro-spinal centre constitute a series of symmetrical pairs, of which twelve issue from the cranium through different apertures in its base, and are thence named cranial. The next following nerve passes out between the occipital bone and the atlas, and the remaining thirty nerves all issue below the successive segments of the vertebral column. The first is sometimes distinguished by the name of suboccipital, but to the whole series of thirty-one nerves the name of spinal will be here given. CRANIAL NERVES. The cranial nerves (nervi cerebrates), besides being distinguished by numbers in the order of their passage through the dura mater lining the cranium, have likewise received other names, according to the place or mode of their distribution, or their functions. The number of the cranial nerves is now universally stated as twelve, following: the enumeration which was proposed by Saemmering in 1778, but has only recently been adopted in this country. Previously they were reckoned as nine pairs, in accordance with the classification of Willis (1664), in which the facial and auditory tog-ether compose the seventh pair, while the glosso-pharyngeal, pneumo-gastric, and spinal accessory are included in the eighth. Willis also looked upon the suboccipital as a cranial nerve, and thus counted ten VOL. m. PT. 2. P 222 THE CRANIAL NERVES. WILLIS. SCEMMERRING. First pair Second of nerves . . i First pair of nerves Second ,. Third Fourth ; ; Third „ Fourth ., Fifth Sixth • | Fifth !, Sixth „ Seventh Eighth C portio dura . | r' \ portio mollis ( n. vagus " ) ( n.accessorms Seventh Eighth ( Ninth \ Tenth ., Eleventh „ Ninth Twelfth Tenth 5> • 1 First ctrvical . pairs. The two arrangements, as well as the special designations of the several nerves, are shown in the following table : — OTHER NAMES. Olfactory nerves. Optic. Common oculomotor. Pathetic or trochlear. Trifacial or trigeminal. Abducent ocular. Facial motor. Auditory. Grlosso-pharyngeal. Pneumo-gastric or vagus. Spinal accessory, Hypoglcssal or lingual motor. Suboccipital. Connection with the cerebro-spinal axis. — The place at which a cranial nerve is attached to the surface of the cerebro-spinal axis is usually termed the Fig. 140. — VENTRAL ASPECT OF THE BRAIN-STEM, SHOWING THE ATTACH- MENTS OF THE PRINCIPAL CRANIAL NERVES. (Allen Thomson.) The full description of this figure will be found at p. 41. The following refer- ences apply to the roots of the nerves: I', right olfactory tract, divided near its; middle ; II, left optic nerve, springing from the commissure, which is concealed by the pituitary body ; II', right optic tract ; the left tract is seen passing back into i arid e, the internal and external corpora geniculata; III, left oculomotor nerve ; IV, trochlear : V, V, large roots of the trifacial nerves ; + + , small roots, the + of the right side is placed on the Gasserian ganglion ; 1, ophthal- mic, 2, superior maxillary, and 3, in- ferior maxillary nerves ; VI, left abducent nerve ; VII, facial ; VIII, auditory ; IX, glosso-pharyngeal ; X, pneumo-gastric ;• XI, spinal accessory ; XII, right hypo- glossal nerve ; at o, on the left side, the rootlets are seen cut short ; C I, sub- occipital or first cervical nerve. superficial origin of the nerve. From this apparent origin the nerve-roots can be traced for a variable depth within the sub-^ stance of the axis to certain col- lections of nerve-cells or nuclei, the connection with which is said to constitute the deep origin of the nerve. It is evident, how- ever, that these terms are pro- perly applicable only to the central connections of the motor or efferent nerves, the fibres of which are outgrowths of nerve-cells contained in the respective nuclei, whereas the sensory or afferent fibres originate generally in the cells of the ganglia found upon the nerve-trunks in the immediate neighbourhood of the axis, and grow MODE OF EXIT FROM THE CRANIUM. 223 inwards to their so-called nuclei, in which they end without forming, so far as is known, any direct connection with the nerve-cells. The superficial attachments of the cranial nerves are quite obvious : the filaments of the first pair spring from the olfactory lobes of the cerebral hemi- spheres ; the second pair arise from the optic thalami and the dorsal part of the mesencephalon ; the third are attached to the crura cerebri or ventral part of the mesencephalon ; the fourth to the valve of Vieussens ; the fifth to the pons ; and the remainder to the medulla oblongata, with the exception of the greater part of the eleventh pair, which arise from the cervical portion of the spinal cord. The course of the fibres within the cerebro-spinal axis, and their connection Fig. 141. — LATERAL VIEW OF THE BRAIN- STEM, SHOWING THE AT- TACHMENTS OK THE CKANIAL NKRVE«. (Allen Thomson.) The full description of this figure will be found at p. 42. The follow- ing references apply to the roots of the nerves ; I, right olfactory tract. cut near its middle ; II, the optic nerves immediately in front of the commissure ; the right optic tract is seen passing back to the thalamus ( Tit ), corpora geniculata (i, c), and corpora quadrigemina (q) ; III, oculomotor nerve ; IV. trochlear nerve arising at v, from the valve of Vieussens ; V, trifacial nerve ; VI, abducent ocular ; VII, VIII, facial and auditory nerves ; between them the pars intermedia ; IX, glosso-pharyngeal ; X, pneumo- ^astric ; XI, spinal accessory ; XII, hypoglossal ; C I, the separate an- terior and posterior roots of the sub- occipital or first cervical nerve. rh. with the nerve-nuclei are more difficult to follow, and in many respects are as yet but imperfectly understood. They have been fully discussed in the accounts of the parts of the spinal cord and brain in which they occur, and to these reference may be made for farther details than are given in the following descriptions. Mode of exit from the cranium. — Each of the cranial nerves, after traversing the subarachnoid space and piercing the arachnoid, from which it receives a sheath generally of very short extent (see p. 188), enters an aperture in the dura mater (in the case of the third, fourth, fifth and sixth nerves at some distance from the osseous foramina by which they emerge), and carries with it in its passage from the cranial cavity a tubular prolongation of that membrane. Some of these nerves, or their main divisions, are contained in distinct foramina of the cranium, others are grouped together in one foramen. The numerous small olfactory nerves descend into the nose through the cribriform plate of the ethmoid bone ; the optic nerve pierces the base of the small wing of the sphenoid bone ; the third, fourth, and sixth nerves, with the ophthalmic division of the fifth, pass through the sphenoidal fissure ; the superior maxillary and inferior maxillary divisions of the fifth pass respectively through the foramen rotundum and foramen ovale of the great wing of the p 2 224 THE CRANIAL NERVES. sphenoid ; the facial and auditory nerves enter the internal auditory meatus of the petrous bone ; the glosso-pharyngeal, pneumo-gastric, and spinal accessory nerves descend through the middle compartment of the jugular foramen between tho petrous and occipital bones ; and the hypoglossal nerve passes through the anterior condylar foramen of the occipital bone. Fig. 142. — A. — SEMIDIAGRAMMATIC VIEW OP A DEEP DISSECTION OF THE CRANIAL NERVES ON THK LEFT SIDE OF THE HEAD. B. — EXPLANATORY OUTLINE OF THE SAME. (Allen Thomson.) £ The Roman numerals from I to XII indicate the roots of the several cranial nerves as they lie in or near their foramina of exit ; V, is upon the large root of the fifth with the Gasserian ganglion in front ; C I, the suboccipital or first cervical nerve ; C VIII, the eighth. The branches of the nerves are marked as follows, viz. : — 1, supraorbital branch of the fifth ; 2, lachrymal passing into the gland ; 3, nasal passing towards the anterior internal orbital canal, and giving the long root to the ciliary ganglion, 4' ; 3', termination of the nasal nerve ; 4, lower branch of the third nerve ; 5, superior maxillary division of the fifth passing into the infraorbital canal ; 5', the same issuing at the infra- orbital foramen and being distributed as inferior palpebral, lateral nasal, and superior labial nerves, 5"; 6, ganglion of Meckel and Vidian nerve passing back from it; 6', palatine and other nerves descending from it ; 6", large superficial petrosal nerve ; 7, posterior dental nerves ; 7', placed in the antrum, which has been opened, points to the anterior dental nerve ; 8, inferior maxillary division of the fifth immediately below the foramen ovale ; 8', some of the muscular branches coming from it ; 8 x , the auriculo-temporal branch cut short, and above it the small superficial petrosal nerve connected with the facial; 9, buccal and external pterygoid; 10, lingual nerve ; 10', its distribution to the side and front of the tongue and to the sublingual gland : 10", submaxillary ganglion ; below 10, the chorda tympani passing forwards from the facial above 12, to join the lingual nerve ; 11, inferior dental nerve; 11', the same nerve and part of its dental distribution exposed by removal of the jaw ; 11", its termination as the mental nerve ; 11"', its mylo-hyoid branch ; 12, twigs of the facial nerve imme- diately after its exit from the stylo-mastoid foramen to the posterior belly of the digastric and to the stvlo-hyoid muscle ; 12', temporo-facial division of the facial ; 12", cervico- facial division ; 13, trunk GENERAL DISTRIBUTION, 225 General distribution. — The greater number of the cranial nerves are entirely confined in their distribution within the limits of the head, as in the case of the first six pairs, the auditory, glosso-pharyngeal, and hypoglossal nerves. Of these, the olfactory, optic, and auditory are restricted to their respective organs of sense ; while the third, fourth, and sixth are exclusively motor nerves in connection with of the glosso-pharyngeal passing round the stylo-pharyngeus muscle after giving pharyngeal and muscular branches ; 13', its distribution on the side and back part of the tongue ; 14, spinal accessory nerve ; 14', the same after having passed through the sterno-mastoid muscle uniting with branches from the cervical nerves ; 15, hypoglossal nerve ; 15', its twig to the thyro-hyoid muscle ; 15", its distribu- tion to the muscles of the tongue ; 16, the descending cervical nerve giving a direct offset to the anterior belly of the omo-hyoid muscle, and receiving the communicating branches 16 x , from the cervical nerves ; 17, pneumo-gastric nerve ; 17', its superior laryngeal branch ; 17", external laryngeal twig; 18, superior cervical ganglion of the sympathetic, uniting with the upper cervical nerves, and giving at 18' the superficial cardiac nerve ; 19, the trunk of the sympathetic ; 19', the middle cervical ganglion, uniting with some of the cervical nerves, and giving 19", the large or middle cardiac nerve ; 20, continuation of the sympathetic down the neck ; 21, great occipital nerve ; 22, third occipital. the muscles of the eyeball and the elevator of the upper eyelid. In the fifth or trifacial nerve all the fibres derived from the large root, and connected with the Gasserian ganglion, are entirely sensory in their function, and constitute the whole of the first and second and the greater part of the third division of the nerve ; but the last of these divisions has associated with it the fibres of the small or motor root, so as to become in some degree a compound nerve. As a nerve of sensation 226 THE CRANIAL NERVES. the trifacial occupies in its distribution the greater part of the head superficially and deeply, excepting that part of the scalp which is situated behind a perpendicular line passing through the external auditory meatus. The muscular distribution of the inferior division of the fifth nerve is chiefly to the muscles of mastication. The glosso-pharyngeal is also a mixed nerve, and is distributed to the tongue, pharynx, and part of the ear-passages ; while the hypoglossal is purely a motor nerve, destined for the muscles of the tongue, its so-called " descending" and other branches, which supply in part the muscles connected with the hyoid bone, being composed of fibres derived from the upper spinal nerves. Fig. 143. —SKETCH OF THE MIDDLE POR- TION OF THE BASE OF THE SKULL, SHOWING THE ENTRANCE OP THK CRANIAL NERVES INTO THE DURA MATER. (Drawn by T. W. P. Lawrence.) The tentorium has bsen divided close to its attachment to the upper border of the petrous. On the right side the nerves are in place ; on the left side they have been removed, and the apertures in the dura mater are seen. Of the remaining nerves, one, the facial, mainly if not exclu- sively motor in function,1 is almost entirely cephalic in its distribu- tion, giving fibres to all the superficial and a few of the deeper muscles of the head ; but one branch passes downwards in the neck to the platysma myoides. Lastly, the tenth or pneumo- gastric and the eleventh or spinal accessory nerves differ from the foregoing in having only a very limited distribution in the head, and in furnishing nerves in much greater proportion to organs situated in the neck and trunk. The first of these, after giving a small branch to the ex- ternal ear, and supplying nerves to the pharynx and larynx, the trachea, gullet, lungs and heart, extends into the abdominal cavity as the principal nerve of the stomach. The other, the spinal accessory, which is classed with the cranial nerves in consequence of its passing out through one of the foramina of the skull, is entirely a motor nerve ; it is partially united with the pneumo-gastric near its origin, and thus furnishes some of the motor fibres of that nerve, but it is mainly distributed in the sterno-mastoid and trapezius muscles. P On pages 224 and 225, fig. 142 is introduced in illustration of the general view of the distribution above given. In this figure the cranium and orbit have been opened up to the depth of the several foramina through which the nerves pass. The greater part of the lower jaw has also been removed on the left side, and the tongue, pharynx, and larynx are 1 It is possible that the chorda tympani branch of the facial may convey sensory (taste) fibres from the tongue. LI&.DENTIC. OLFACTORY NERVES. 227 partially in view. The occipital bone has been divided by an incision passing down from the occipital protuberance and through the condyle to the left of the foramen magnum. The cervical vertebras have been divided to the left of the middle, and the sheath of the spinal cord opened so as to expose the roots of the cervical nerves. I.— OLFACTORY NERVES. The olfactory nerves are 8lender filaments, about twenty in number, which spring from the under surface of the olfactory bulb, and descend to the nose through the foramina in the cribriform plate of the ethmoid bone, each being invested by tubular prolongations of the membranes of the brain. They form an inner group, which are lodged for a short distance in grooves on the surface of the vertical plate of the ethmoid, and then break up into tufts of branches before being distributed to the mucous membrane over the upper part (1 to 1*5 cm.) of that bone, and an outer Fig. 144. — DISTRIBUTION OF THE OLFACTORY NERVFS ON THE SEPTUM OF THE NOSE. (From Sappey, after Hirschfeld and LeveiHe". ) f The septum is exposed and the anterior palatine canal opened on the right side. I, points to the olfactory bulb, and the remaining Roman numbers to the several cranial nerves ; 1, the olfactory nerves as they pass through the cribriform plate ; 2, internal twig of the nasal branch of the ophthalmic nerve ; 3, naso-palatine nerve. The area of distribution of the olfactory nerves is represented too large. group which ramify over the mesial surface of the lateral mass of the ethmoid, for a similar extent. The olfactory fibres do not reach the lower edge of the superior, or any part of the middle and lower turbinate bones.1 The olfactory nerves are composed exclusively of non-medullated fibres, and their branches communicate freely with each other as they descend, thus giving rise to a narrow meshed plexus beneath the mucous membrane, especially on the outer wall of the fossa. (See also the anatomy of the nose.) II.-OPTIC NERVE. The second pair or optic nerves of the two sides meet each other at the optic commissure where they partially decussate. From this point they may be traced backwards round the crura cerebri, under the name of the optic tracts. The optic tract arises from the pulvinar of the optic thalamus, the geniculate bodies, and the superior quadrigeminal body. As it leaves the under part of the thalamus it makes a sudden bend forwards, and then runs, in the form of a flattened band, obliquely inwards across the upper part of the anterior surface of 1 A. v. Brunn. "Beitriigezur mikroskopischen Anatomic der menschlichen Nasenhohle." Arch. f. mikroskop. Anat. xxxix, 1892. 228 THE CRANIAL NERVES. the cerebral peduncle, to which it is closely attached ; after this, becoming more nearly cylindrical, it is continued between the tuber cinereum and the anterior perforated space, adhering- to the basal grey matter of the cerebrum, and thus reaches the optic commissure. th-i fithqerv. fe. sup. braclv. \nf, \irach. ttcl.l. .b. tania. sentif-. ank.perf sp Fig. 145. — ORIGIN AND RELATIONS OF THE OPTIC TRACT. (Gr. D. T. ) The mid-brain has been divided immediately above the pons, and the part is viewed from below. o»fc. mrtte The optic commissure or chiasma is of an oblong form, the longer diameter (10 — 12 mm.) being directed transversely. It rests upon the olivary eminence of the sphenoid bone, and the in- ternal carotid artery, ascend- ing to the brain, is close to it on each side. A large number of the fibres of the two nerves decussate in the commissure, but some are continued from the tract to the nerve of the same side, while those fibres of the tract which come from the internal geniculate body do not pass into either optic nerve, but cross in the hinder part of the chiasma to the opposite tract, constituting the inferior commissure of Gudden (see p. 118). The optic nerve proper runs from the commissure forwards and outwards through the optic foramen, having the ophthalmic artery to its lower and outer side. As it enters the foramen it receives a strong sheath from the dura mater, and a slender one from the arachnoid, both of which are prolonged as far as the eyeball. Appear- ing in the orbit between the origins of the recti muscles, it continues its oblique course, inclining at the same time somewhat downwards, to the eyeball, which it enters on its posterior aspect about 3 mm. internal to its centre. Here the nerve perforates the sclerotic and choroid coats, and terminates by expanding in the retina (see the anatomy of the eye). The nerve has a diameter of 3 — 4 mm., and is from 30 to 40 mm. long. Its intraorbital part measures from 20 to 30 mm., and has a slightly flexuous course, its length exceeding the distance in a straight line from the optic foramen to the eyeball by about 5 mm., so as to allow of the move- ments of the latter. It is surrounded by the ciliary vessels and nerves, and is pierced about 10 mm. behind its termination by the central artery of the retina, which, with a companion vein, runs in the axis of the nerve to the eyeball. The number of fibres in the optic nerve is estimated at somewhat less than half a million (Salzer) ; they are mostly of small size. Varieties. — In a few rare instances absence of the optic commissure has been met with, each optic tract being continued directly into the optic nerve, and passing- to the eyeball, of the same side. In some cases it would appear that the decussation of the fibres in the commissure is complete (see p. 118). III.— OCULOMOTOK NERVE. The third nerve, the common motor nerve of the eyeball (motor oculi), gives branches to all the muscles of the orbit, with the exception of the superior oblique and external rectus. It also supplies, through its connection with the ciliary ganglion, the sphincter muscle of the iris and the ciliary muscle of the eyeball. THE THIRD NERVE. 229 The fibres of the nerve spring mainly from the oculomotor nucleus in the grey matter of the floor of the aqueduct of Sylvius opposite the superior quadrigeminal N.HI Fig. 146. — PLAN OF THE ORIGINS OP THE THIRD, FOURTH AND SIXTH NERVES. (Modified from Gowers. ) The nerves and their nuclei are projected into the outline of a median section of the mid brain, and pons : III, third nerve ; N.III, its nucleus; IV, fourth nerve; N.IV, its nucleus; P.L. B., posterior longitudinal bundle; VI, sixth nerve; N.VI, its nucleus. body (figs. 146 and 151) ; to these are added others which ascend in the posterior longitudinal bundle from the nucleus of the sixth nerve of the opposite side. They pass ventrally through the tegmentum, and emerge in ten to fifteen bundles from the inner side of the crus cerebri, commencing close to the upper border of the pons, and extending upwards and outwards along the line of the oculomotor groove. One of these bundles is frequently separated from the rest, and issues more externally from the anterior surface of the crus. internal carotid artcry'ty posterior communicating- artery posterior cerebral artery inferior longitudina^ sinus — optic nerve fc— third nerve tjjs' --fourth nerve superior cerebellar artery /_' — tentorium inferior quadrigeminal body V *2&7 -£ — -\- falx cerebri Fig. 147. — THE THIRD AND FOURTH NERVES IN THEIR INTRACRANIAL COURSE. (Drawn by T. W. P. Lawrence.) The mid-brain is divided in the aperture of the tentorium, and the cerebrum removed. On the right side the posterior cerebral and posterior communicating arteries are cut short in order to expose the origin of the third nerve. On the left side the tentorium and crus cerebri are slightly separated so as to show the fourth nerve more fully. 230 THE CRANIAL NERVES. Speedily becoming firm and round, the nerve is directed from the interpeduncular space forwards, as well as somewhat outwards, between the posterior cerebral and superior cerebellar arteries to the outer side of the posterior clinoid process, a little anterior to which it penetrates the layer of dura mater forming the outer boundary of the cavernous sinus. Contained within this membrane, it continues its course Fig. 148. — PLAN OF THE THIRD NERVE, WITH THE CILIARY GANGLION. (G. D. T.) The ganglion is seen to be attached by its short root to the nerve of the inferior oblique muscle ; LR, its long, and SR, its sympathetic root. forwards to the inner end of the sphenoidal fissure, and there divides into two parts, upper and lower, which enter the orbit between the heads of the external rectus muscle, and are separated from each other by the nasal branch of the ophthalmic nerve. As the third nerve lies in the outer wall of the cavernous sinus, it is con- nected by slender filaments with the cavernous plexus of the sympathetic, and it receives also a small branch from the ophthalmic division of the fifth nerve. The upper, the smaller part, is directed inwards over the optic nerve to the Fig. 149. — VIEW FROM ABOVE OF THE MOTOR NKRVKS OF THE EYEBALL AND ITS MUSCLES (after Hirschfeld and Leveille, altered). (Allen Thomson. ) The ophthalmic division of the fifth pair has been cut short ; the attachment of the muscles round the optic nerve has been opened up, and the three upper muscles turned towards the inner side, their anterior parts being removed ; a part of the optic nerve is cut away to show the inferior rectus ; and a part of the sclerotic coat and cornea is dissected off showing the ins, ciliary muscle, and choroid coat, with the ciliary nerves. «, upper part of the internal carotid artery emerging from the cavernous sinus ; b, superior oblique muscle ; b't its anterior part passing through the pulley ; c, levator palpebrse superioris ; d, superior rectus ; e, internal rectus ; f, external rectus ; f, its upper tendon turned down ; g, inferior rectus ; h, insertion of inferior oblique muscle. II, optic commissure ; II', part of the optic nerve entering the eyeball ; III, common oculomotor ; IV, trochlear nerve ; V, large root of fifth ; V, small or motor root ; VI, abducent nerve ; ] , upper division of third nerve, giving twigs to the levator palpebrse and superior rectus ; 2, branches of lower division supplying the internal and inferior recti muscles ; 3, the long branch of the same nerve pro- ceeding forwards to the inferior oblique muscle, and close to the number 3, the short root of the ciliary ganglion : this ganglion is also shown, receiving from behind its long root, which has been cut short, and giving forward some of its ciliary nerves, which pierce the sclerotic coat ; 3', marks the termination of some of these nerves in the ciliary muscle and iris after having passed between the sclerotic and choroid coats ; 4, the trochlear nerve entering the upper surface of the superior oblique muscle ; 6, the abducent nerve passing into the external rectus. superior rectus muscle of the eye and the elevator of the eyelid, to both of which muscles it furnishes branches. The lower and larger portion of the nerve divides into three branches ; of these one reaches the inner rectus ; another the lower rectus ; and the third, the longest of the three, runs onwards between the lower and the outer rectus, and terminates below the ball of the eye in the inferior oblique muscle. The last-mentioned branch is connected with the lower part of the ciliary ganglion by a short thick offset (short root of the ganglion), and gives one or two filaments to the lower rectus muscle. THE THIRD AND FOURTH NERVES. The several branches of the third nerve enter the muscles to which they are dis- distributed on the surface which in each is turned towards the eyeball, with the exception of that to the inferior oblique, which penetrates the hinder border of its muscle. The fibres of the third nerve, about 15,000 in number, are generally large ; but there are some small ones, most of which pass into the ciliary ganglion. In the rootlets of the nerve Thomsen and G-askell have described a peculiar structure which is regarded by them as the remains of a degenerated ganglion (Virchow's Archiv, cix, 1887 ; Journ. Phys., x, 1889, p. 167). Varieties.— A communication between the third and sixth nerves as they pass the cavernous sinus has been described, but its existence is denied by most recent observers. The upper division of the third nerve may have a communication with the nasal (Svitzer, Sommering, Testut). The third nerve has been seen in a few cases giving a branch to the external rectus (Cruveilhier, Fasebeck, C. Krause). and in one instance a branch of the third supplied the place of the sixth nerve which was wanting (Generali). A filament to the superior oblique muscle is noticed by Volkmann. The branch to the inferior oblique muscle was seen by Arnold to pass through the lower part of the lenticular ganglion, and by Henle to pierce the inferior rectus. POSITION OF CERTAIN NERVES AT THE CAVERNOUS SINUS, AND AS THEY ENTER THE ORBIT. — There are several nerves, besides the third, placed close together at the Fig. 150. — THE NERVES IN THE OUTER WALL OF THE CAVERNOUS SINUS, SEEN IN TRANSVERSE SECTION. (Langer.) ^ OPHTn. NERVE n INT. CAR. Af! cavernous sinus, and entering the orbit through the sphenoidal fissure. To avoid repetition hereafter, the relative positions of these nerves may now be described. The nerves thus associated are the third, the fourth, the ophthalmic division of the fifth, and the sixth. At the cavernous sinus. — In the dura mater which bounds the cavernous sinus on the outer side, the third and fourth nerves and the ophthalmic division of the fifth are placed, as regards one another, in their numerical order both from above downwards and from within outwards. The sixth nerve is placed separately from the others close to the carotid artery in the cavity of the sinus, and internally to the ophthalmic nerve. Near the sphenoidal fissure, through which they enter the orbit, the relative position of the nerves is changed, the sixth nerve being here close to the rest, and their number is augmented by the division of the third and the ophthalmic nerves — the former into two, the latter into three parts. In the sphenoidal /insure. — The fourth and the frontal and lachrymal branches of the fifth, which are here higher than the rest, lie on the same level, the fourth being the nearest to the inner side, and enter the orbit above the muscles. The remaining nerves pass between the heads of the external rectus muscle, in the following order from above downwards ; the upper division of the third, the nasal branch of the fifth, the lower division of the third, and, lowest of all, the sixth. IV.— TROCHLEAR NERVE. The fourth, trochlear, or pathetic nerve is the smallest of the cranial nerves, and has the longest course within the cranial cavity. It is distributed solely to the superior oblique muscle of the eye. The nucleus of the fourth nerve continues downwards the column of cells giving origin to the third nerve, being placed in the ventral grey matter of the aqueduct of 232 THE CRANIAL NERVES. Sylvius opposite the upper part of the inferior quadrigeminal body (fig. 146). From the nucleus the fibres are directed at first downwards for a short distance, and then backwards and inwards, arching round the lower part of the aqueduct, to enter Fig. 151. — PLAN OP THE ORIGINS OF THE THIRD AND FOURTH NERVES. (G. D. T.) The midbrain is supposed to be divided at different levels on the two sides, the section on the right side of the figure passing through the superior, and on the left side through the inferior quadrigeminal body : III, third nerve ; N.I II, its nucleus ; IV, fourth nerve ; N.IV, its nucleus ; V.D, descending or mesenceohalic root of the fifth nerve; N. V, its nucleus; C.Q.S, superior, and C.Q.I, inferior quadrigeminal body; P.L.B., posterior longitudinal bundle. the superior medullary velum, where they cross to the opposite side, the two nerves thus forming a complete decussation. Emerging from the upper end of the superior medullary velum close to the frenulum, and immediately below the inferior quadrigeminal body, the fourth nerve is directed at first outwards across the superior peduncle of the cerebellum, and then turns forwards round the outer side of the crus cerebri (figs. 141, 147), lying parallel to and between the posterior cerebral and superior cerebellar arteries. It enters an Fig. 152. — VIEW FROM ABOVE OP THE UPPER- MOST NERVKS OF THE ORBIT, THE GASSERIAN GANGLION, &c. (From Sappey, after Hirsch- feldandLeveille".) § I, olfactory tract, passing forwards into the bulb; II, optic commissure; III, oculomotor; IV, trochlear nerve ; V, large root of the fifth nerve, a small portion of the lesser root is seen below it; VI, sixth nerve ; VII, facial ; VIII, audi- tory ; IX, glosso-pharyngeal ; X, pneumo-gastric ; XI, spinal accessory ; XII, hypoglossal : 1, Gras- serian ganglio^ ; 2, ophthalmic nerve ; 3, lachry- mal nerve ; 4, frontal ; 5, external, 6, internal branch of the supraorbital nerve ; 7, supratro chlear nerve ; 8, nasal nerve ; 9, its infratro- chlear branch ; 10, nasal nerve, passing through the anterior internal orbital canal ; 11, anterior deep temporal proceeding from the buccal nerve; 12, middle deep temporal ; 13, posterior deep temporal arising from the masseteric ; 14, origin of the auriculo-temporal ; 15, great superficial petrosal nerve. aperture in the dura mater immediately beneath the free margin of the ten- torium, a little behind the posterior clinoid process, and runs forwards in the outer wall of the cavernous sinus, resting against the upper margin of the ophthalmic nerve, and crossing the third obliquely on its outer side from below upwards, to the inner end of the sphenoidal fissure. Passing into the orbit above the external rectus muscle, it inclines inwards over the levator palpebrae and superior rectus, and finally enters the superior oblique muscle on its upper surface, and close to its outer border. THE FIFTH NERVE. 233 While lodged in the outer wall of the sinus, the fourth nerve is connected with the sympathetic on the carotid artery, and is also joined by a filament from the ophthalmic nerve. The fourth nerve consists of about 1,200 fibres, mostly of large size. It also shows close to its origin the vestiges of a degenerated ganglion (Gaskell). Varieties. — In one case the fourth nerve pierced the levator palpebras superioris on its way to the superior oblique (G-. D. T.). The nerve has been observed in several cases sending a branch forwards to the orbicularis palpebrarum muscle, or to join the supratrochlear, the infratrochlear, or the nasal nerve. A communication with the frontal nerve is recorded by Berte. V. — TRIFACIAL NERVE. The fifth, trifacial, or trigeminal nerve is the largest of the cranial nerves, and resembles a spinal nerve in the circumstance that it arises by separate sensory and Fig. 153. — PLAN OP THE ORIGIN OF THE FIFTH NERVE. The outline represents the contour of the medulla ohlongata, pons, and a part of the raidbrain, which are supposed to be transparent : V.M., motor portion of the fifth nerve ; N.V.M., the motor nucleus; V.D., descending or mesencephalic root; \r.S., sensory portion of the fifth nerve; N.V.S., the upper sensory nucleus ; V.A., asoending or bulbar root ; S.GLR., gelatinous substance of llolando, or lower sensory nucleus. motor roots, and also that the sensory fibres pass through a ganglion while the motor do not. Its sensory division, which is much the larger, imparts common sensibility to the face and the fore part of the head, as well as to the eye, the nose, the external ear, and the mouth, including the greater portion of the tongue ; it may possibly also confer the power of taste upon the fore part of the latter organ. The motor root supplies chiefly the muscles of mastication. The two roots of the nerve appear at the side of the pons Yarolii, where the transverse fibres of the latter are prolonged into the middle peduncle of the cerebellum, and much nearer its upper than its lower border. The small root issues above the large one, and the two are separated from one another by a small band of the cross fibres of the pons. The fibres of the small root arise in part from the motor nucleus of the fifth nerve beneath the floor of the upper portion of the fourth ventricle ; they are joined by the bundle known as the descending root of the fifth nerve, which springs from a collection of large nerve-cells in the grey matter at the side of the aqueduct of Sylvius. The fibres of the large root pass backwards into the pons, and some reach the upper sensory nucleus of the fifth nerve, placed to the outer side of and somewhat deeper than the motor nucleus ; but the greater number turn downwards and are continued through the substance of the pons into the medulla oblongata, forming the so-called ascending or bulbar root of the fifth nerve : their mode of termination is uncertain, but they may break up among the cells of the gelatinous substanca of Rolando (lower sensory nucleus of the fifth nerve). The small root consists mainly of large fibres, and contains a vestigial ganglion (Gaskell). The large root is mostly composed of fine fibres. 234 THE CKAN1AL NEBVE8. From the pons, the two roots are directed forwards beneath the anterior extremity of the tentorium to the middle fossa of the base of the skull, and enter a recess in the dura mater (cavum MecTceUi) over the summit of the petrous part of the temporal bone. Here the large root becomes expanded, and its funiculi divide and unite so as to form a plexiform network which is continued into the Gasserian ganglion. The small root inclines downwards on the inner side of the large root, and then passes outwards beneath the ganglion, without its fibres ? being incorporated in any way with the latter, to join below the foramen ovale the lowest of the three trunks issuing from the ganglion. The ganglion of the fifth nerve or Gasserian ganglion (ganglion semilunare) occupies a depression on the upper surface of the petrous portion of the temporal bone, near the apex, and is somewhat crescentic in form, the convexity being turned forwards. It is flattened, and striated on the surface. Its internal part Fig. 154.— GENERAL PLAN OF THE BRANCHES OF THE FIFTH PAIR. (After a sketch by Charles Bell.) ^ 1, small root of the fifth nerve ; 2, large root, passing forwards into the (rasserian ganglion ; 3. placed on the bone above the ophthalmic nerve, which is dividing into the frontal, lachrymal, and nasal branches, the latter connected with the ciliary ganglion ; 4, placed on the bone close to the foramen rotundum, marks the superior maxillary division, which is connected below with the spheno-palatine ganglion, and passes forwards to the infraorbital foramen ; 5, placed on the bone over the foramen ovale, marks the inferior maxillary nerve, giving off the auriculo-temporal and muscular branches, and continued by the inferior dental to the lower jaw, and by the lingual to the tongue ; a, submaxil- lary gland, the submaxillary ganglion placed above it in connection with the lingual nerve ; 6, chorda tympani ; 7, facial nerve, issuing from the stylo- mastoid foramen. comes into close relation with the posterior extremity of the cavernous sinus and the internal carotid artery. On its inner side the ganglion is joined by filaments from the carotid plexus of the sympathetic nerve ; and, according to some anatomists, it furnishes from its back part filaments to the dura mater. The cells of this ganglion are similar to those found on the posterior roots of the spinal nerves. From the convex border of the Gasserian ganglion proceed the three large divisions of the nerve. The highest (first or ophthalmic trunk) enters the orbit ; the second, the superior maxillary nerve, is continued forwards to the face between the orbit and mouth ; and the third, the inferior maxillary nerve, is distributed chiefly to the external ear, the tongue, the lower teeth, the face below the mouth, and the muscles of mastication. The first two trunks proceed exclusively from the ganglion and are entirely sensory, while the third or inferior maxillary trunk, derived principally from the ganglion, has associated with it also the whole of the fibres of the motor root, and thus distributes both motor and sensory branches. THE LACHRYMAL NERVE. 235 I.— OPHTHALMIC NERVE. The ophthalmic nerve, or first division of the fifth, the smallest of the three offsets from the Gasserian ganglion, is flattened from side to side, and measures about an inch in length. It is directed forwards and upwards in the outer wall of the cavernous sinus, in company with the third and fourth nerves, towards the sphenoidal fissure, where it ends in branches which pass through the orbit to the surface of the head and to the nasal fossa. In its course forwards, the ophthalmic nerve is joined by filaments from the cavernous plexus of the sympathetic. BRANCHES. — A small recurrent branch (nerrus tentorii) arises from the ophthalmic trunk near the Gasserian ganglion, and, running backwards across the fourth nerve, to which it generally adheres closely for some distance, ramifies between the layers of the ten tori am. Farther forwards the ophthalmic nerve gives off three slender offsets which join respectively the third, fourth, and sixth nerves as they enter the orbit. The terminal branches resulting from the division of the ophthalmic nerve close to the orbit are the nasal, which is usually the first to arise and springs from the inner and lower part of the trunk, the frontal and the lachrymal. These branches Fig. 155.— PLAN OF THE OPHTHALMIC NERVE. (GK D. T.) The dotted line repi-esents the limit of the orbit, c G, ciliary ganglion, joined behind by the long root, and giving off in front the short ciliary nerves. aie transmitted separately through the sphenoidal fissure, and are continued through the orbit (after supplying some filaments to the eyeball and the lachrymal gland) to their final, distribution in the nose, the eyelids and the integument of the forehead. Lachrymal nerve. — The lachrymal ne"rve (fig. 152, 3) is external to the frontal at its origin, and is contained in a separate sheath of dura mater. In the orbit it passes along the outer part, above the external rectus muscle, to the outer and upper angle of the cavity. Near the lachrymal gland, the nerve has a connecting filament with the temporal branch of the superior maxillary nerve ; and when in close apposition with the gland, it gives many filaments to that body and to the conjunctiva. Finally, the lachrymal nerve penetrates the palpebral fascia externally, and ends in the upper eyelid, and the skin in the neighbourhood of the external angular process of the frontal bone, the terminal ramifications being joined by twigs from the facial nerve. Varieties.— The lachrymal nerve is occasionally smaller than usual, being reinforced by a twi"- from the temporal branch of the superior maxillary, and it has been seen replaced entirely by an offset of the latter nerve (Turner, Hyrtl). On the other hand, the lachrymal nerve has been found sending an offset through the malar bone in the place of the temporal branch of the superior maxillary nerve, which was absent (G. D. T.). The lachrymal branch sometimes appears to be derived in part from the fourth nerve, but in such cases" the additional root is probably composed of fibres that have passed over from the ophthalmic to the fourth, while these nerves are contained in the outer wall of the cavernous sinus. 236 THE CRANIAL NERVES. Frontal nerve. — The frontal nerve (fig. 152, 4), the largest division of the ophthalmic, also enters the orbit above the muscles, and runs forwards between the elevator of the upper eyelid and the periosteum. About the middle of the orbit it divides into two branches, supratrochlear and supraorbital. (a) The supratrochlear nerve, much the smaller of the two branches, inclines inwards towards the pulley of the superior oblique muscle, close to which it sends a filament downwards to communicate in a loop with the infratrochlear branch of the nasal nerve, and then leaves the orbit between the orbicularis palpebrarum muscle and the bone. In this position the nerve gives twigs to the skin and conjunctiva of the upper eyelid, and finally it turns upwards, dividing into branches which per- forate the orbicularis and frontalis muscles, and are distributed to the integument of the lower and mesial part of the forehead. (b) The supraorbital nerve is the continuation of the frontal nerve, and leaves the orbit by the supraorbital notch or foramen. It divides into two branches, inner and outer, wrhich ascend on the forehead beneath the frontalis muscle, and are dis- tributed by numerous slender ramifications to the skin of the fore and upper parts of the scalp. The outer branch is the larger, and extends backwards nearly to the lambdoid suture ; the inner branch reaches but a little way over the parietal bone. In the supraorbital notch a slender filament of the nerve enters an aperture in the frontal bone, where it is said to be distributed to the diploe and the mucous lining of the frontal sinus ; as the nerve emerges from the orbit, twigs are sent downwards to the upper eyelid ; and from its terminal divisions small branches pass to the pericranium. The primary division of the supraorbital nerve often takes place before it issues from the orbit, and in that case only the larger branch passes through the supra- orbital notch, the smaller one being placed more internally, and not unfrequently traversing a second slighter notch (frontal notch, Henle) in the orbital margin (fig. 152, 5, 6). The branches of the supraorbital nerve, and the same is the case with all the cutaneous offsets of the fifth, form communications with the adjacent ramifications of the facial nerve ; in this way sensory fibres derived from the fifth nerve may be conveyed to the surrounding muscles. Nasal nerve. — The nasal nerve (oculo-nasal or naso-ciliary} enters the orbit between the heads of the external rectus muscle, and between the two divisions of the third nerve. It then inclines inwards over the optic nerve, passing beneath the superior rectus and superior oblique muscles, to the inner side of the orbit, and leaves that cavity by the anterior internal orbital canal. In this part of its course it furnishes a slender branch to the ciliary ganglion, one or two filaments (long ciliary) directly to the eyeball, and a considerable infratrochlear branch, which arises just before the nerve enters its canal on the inner side of the orbit. Arrived in the cranial cavity, the nerve is directed forwards in a groove at the outer edge of the cribriform plate of the ethmoid bone to a small canal between the fore part of the plate and the frontal bone, through which it descends to the nasal fossa. Here it gives off internal or septal and external branches to the mucous membrane of the fore part of the nasal fossa, and is then continued downwards in the groove on the back of the nasal bone, to terminate as the anterior or. superficial branch in the integument of the lower part of the nose. (a) The branch to the ciliary ganglion, very slender, and from a quarter to half an inch in length, arises generally between the heads of the external rectus. It lies on the outer side of the optic nerve, and enters the upper and back part of the ganglion, constituting its long root. (b) The long ciliary nerves are situated on the inner side of the optic nerve ; THE NASAL NERVE. 237 they join one or more of the short ciliary branches from the ciliary ganglion, and, after perforating the sclerotic coat of the eje, are distributed in the same manner as those nerves. (c) The wfmtrochlear nerve runs forwards along the inner side of the orbit, below the superior oblique muscle, and parallel to the supratrochlear nerve, from which it receives, near the pulley of the oblique muscle, a filament of connection. The nerve is then continued below the pulley to the inner angle of the eye, and ends, in filaments which supply the conjunctiva, the caruncle, and the lachrymal sac, as well as the integument of the upper eyelid and root of the nose (fig. 171, 22). (d) The internal or septal branch (fig. 144, 2) supplies the pituitary membrane over the fore part of the septum, extending downwards nearly as far as the opening of the nostril. (e) The external branch (fig. 160, 2), often represented by two or three filaments, is distributed to the mucous membrane of the fore part of the outer wall of the nasal fossa, including the anterior ends of the middle and lower turbinate bones. (/) The anterior or superficial branch (fig. 171, 24) issues between the nasal bone and the upper lateral cartilage of the nose, and runs downwards under cover of the compressor naris muscle to the tip of the nose, supplying the skin of the lower part of the organ. Varieties. — The nasal nerve occasionally (frequently, Krause) gives filaments to the superior and internal recti muscles. A branch to the levator palpebrse superioris has also been met with (Fasebeck). In one case filaments of communication passed from a small gang-lion connected with the nasal nerve to the third and sixth nerves (Svitzer). In tvro instances Testut observed absence of the inf ratrochlear branch, its place being supplied by the supratrochlear nerve. Offsets from the nasal nerve, as it traverses the anterior internal orbital canal, to the frontal sinus and ethmoidal cells are described by Meckel and Langen- beck ; and a tpheno-ethmoidal (Luschka) or posterior ethmoidal (Krause) branch is said to pass through the posterior internal orbital canal to the mucous membrane of the sphenoidal sinus and posterior ethmoidal cells. SUMMARY. — The first division of the fifth nerve is altogether sensory in function. It furnishes branches to the dura mater ; to the eyeball and the lachrymal gland ; to the mucous membrane of the nose and eyelids ; to the integument of the nose, the upper eyelid, the forehead, and the upper part of the hairy scalp. It has com- munications with the third, fourth, and sixth nerves, with numerous branches of the facial, and with the sympathetic. Ciliary Ganglion. There are four small ganglia connected with the divisions of the fifth nerve : the ciliary ganglion with the first, the spheno-palatine ganglion with the second, and the otic and submaxillary ganglia with the third. These ganglia, besides receiving branches from the sensory part of the fifth, are each connected with a motor nerve from the third, the fifth, or the facial, and with twigs from the sympa- thetic ; and the nerves thus joining the ganglia are named their roots. The ciliary, ophthalmic, or lenticular ganglion serves as a centre for the supply of nerves — motor, sensory, and sympathetic — to the eyeball. It is a small reddish body, compressed laterally and somewhat four-sided, and measures about 2 mm. from before back. It is situated at the back of the orbit, between the outer •rectus muscle and the optic nerve, and generally in contact with the ophthalmic artery ; it is joined behind by branches from the fifth, the third, and the sympa- thetic nerves ; while from its fore part proceed the short ciliary nerves to the eyeball. The cells of the ganglion are of the multipolar variety. VOL. III. PT. 2. Q 238 THE CEANIAL NERVES. UNION OF THE GANGLION WITH NERVES : ITS BOOTS. — The posterior border of the ganglion receives three nerves. One of these, the long or sensory root, a slender filament from the nasal branch of the ophthalmic trunk, joins the upper part of this border. Another branch, the short or motor root, much thicker and shorter than the preceding, and sometimes divided into two parts, is derived from the branch of the third nerve to the inferior oblique muscle, and is connected with the lower part of the ganglion. The middle or sympathetic root is a very small nerve which emanates from the cavernous plexus of the sympathetic, and reaches the ganglion close to the long upper root : these two nerves are frequently conjoined before reaching the ganglion. The ganglion is sometimes very small, probably from the nerve-cells being distributed along the nerves which are connected with it. BRANCHES OF THE GANGLION. — From the fore part of the ganglion arise six or eight short ciliary nerves, which undergo division as they pass forwards, so that they form from twelve to twenty fine filaments as they reach the eyeball. They are dis- Fig. 156.— NERVES OF THE ORBIT FROM THE OUTER, SIDE. (From Sappey, after Hirscli- feldandLeveille.) f The external rectus muscle has been divided and turned down : 1, optic nerve ; "2, trunk of the third nerve ; 3, its upper division passing into the levator palpebrre and superior rectus ; 4, its long lower branch to the inferior oblique muscle ; 5, the sixth nerve joined by twigs from the sympathetic ; 6, Gasserian ganglion ; 7, ophthalmic nerve ; 8, its nasal branch ; 9, ciliary ganglion ; 10, its short, 11, its long, and 12, its sympathetic root ; 13, short ciliary nerves ; 14, supraorbital nerve. posed in two bundles, springing from the upper and lower angles of the ganglion, and being placed, the one set above, the other below the optic nerve. The lower set is the more numerous, and is accompanied by the long ciliary nerves (from the nasal), with which one or more of these branches are joined. Having entered the eyeball by apertures in the back part of the sclerotic coat, the nerves are lodged in grooves on its inner surface, and are finally distributed to the ciliary muscle, the iris and the cornea (see the anatomy of the eye). Varieties.— Additional roots to the ciliary ganglion have been observed by many anatomists, derived from the upper division of the third nerve, from the fourth nerve, from the lachrymal nerve, from the spheno-palatine ganglion, or from the sixth nerve. Absence of the long root is recorded : in this case it is probable that the corresponding* fibres pass directly from the nasal by the long ciliary nerves to the eyeball. The sympathetic root may be represented by several fine filaments proceeding from the cavernous plexus : according to Reichart this is the normal arrangement, the majority of the filaments accompanying the third nerve. II.— SUPERIOR MAXILLARY NERVE. The superior maxillary nerve, or second division of the fifth (n. mazilfaris), is intermediate in size between the ophthalmic and the inferior maxillary trunks. It commences at the middle of the Gasserian ganglion, and, passing horizontally forwards, soon leaves the skull by the foramen rotundum of the sphenoid bone. The nerve then crosses the spheno-maxillary fossa, and, taking the name of infraor~bital> enters the infraorbital canal of the upper maxilla, by which it is conducted to the face. After emerging from the infraorbital foramen, it terminates beneath the elevator of the upper lip in branches, which spread out to the side of the nose, the lower eyelid, and the upper lip. THE SUPERIOR MAXILLARY NERVE. 239 BRANCHES. — Near its origin a fine recurrent branch (n. meninyeus medius) passes to the dura mater and middle meningeal artery. In the spheno-maxillary fossa an orbital or temporo-malar branch ascends from the superior maxillary nerve to the Fig. 157. — SUPERIOR MAXILLARY NEIIVE AND SOME OF THE ORBITAL NERVES. (From Sappey, after Hirschfeld and Leveilk'. ) I 1, Gasserian ganglion ; 2, lachry- mal nerve ; 3, trunk of the superior maxillary nerve ; 4, its orbital branch ; 6, origin of its malar twig ; 7, its temporal twig, joined by 5. the com- municating branch from the lachrymal nerve ; 8, spheno-palatine ganglion ; 9, Yidian nerve : 10, its upper branch or great superficial petrosal nerve proceeding to join 11, the facial nerve ; 12, its lower branch or great deep petrosal nerve joining the sympa- thetic; 13, 14, posterior dental nerves; 16, terminal branches of the infra- orbital nerve in the face ; 16, a branch of the facial uniting with some of the twigs of the infraorbital. orbit, and two spheuo-palatine branches descend to join Meckel's ganglion ; while the nerve is in contact with the upper maxilla, it furnishes the superior dental or alveolar branches ; and on the face are the terminal branches already indicated. Fig. 158. — PLAN OF THE SUPERIOR MAXILLARY NERVE. (G. D. T.j Orbital branch. — The orbital or temporo-malar branch (n. zygcmaticus}, a small cutaneous nerve, enters the orbit by the spheno-maxillary fissure, and imme- diately divides into two branches (temporal and malar), which pierce the malar bone, and are distributed to the temple and the prominent part of the cheek. (a) The temporal branch (r. zygomaticotemporatts) is directed upwards in a groove on the outer wall of the orbit, and leaves this cavity by the temporal canal Q2 240 THE CRANIAL NERVES. in the malar bone. While still in the orbit, it is joined by a communicating filament (in some cases by two filaments) from the . lachrymal nerve. The nerve is then inclined upwards in the temporal fossa between the bone and the temporal muscle, and perforating the aponeurosis over the muscle nearly an inch above the zygoma, ends in cutaneous filaments over the fore part of the temporal region. The cutaneous ramifications are united with the facial nerve, and sometimes with the auriculo-temporal branch of the third division of the fifth. (#) The malar branch (r. zygomalicofacialis) lies at first in the loose fat in the lower angle of the orbit, and is continued to the face through the malar canal of the malar bone, where it is frequently divided into two filaments. It is distributed to the skin over the malar bone, after forming a communication with the facial nerve. Varieties. — The temporo -malar nerve is subject to frequent deviations from the arrange- ment above described. Thus, either branch may be smaller than usual, or even absent, in which case the other division of the nerve may be distributed over a larger area, or the temporal branch may be reinforced or replaced by the lachrymal nerve, the malar branch by the infraorbital nerve. The temporal branch, instead of perforating the malar bone frequently passes into the temporal fossa through the anterior end of the spheno-maxillary fissure. The superior dental or alveolar nerves are, as a rule, three in number, anterior, middle, and posterior, but the middle is sometimes conjoined with the anterior, while the posterior is frequently represented by two separate offsets. Fig. 159. — DEEP VIEW OF THE SUPERIOR MAXILLARY SERVE AND THE SPHF.XO- PALATINE GANGLION, &C, (From Sappey, after Hirschfeld and Leveille.) I 1, superior maxillary nerve ; 2, posterior superior dental ; 3, middle superior dental ; 4, anterior superior dental ; 5, superior dental plexus ; 6, spheno-palatine ganglion ; 7, Vidian nerve ; 8, its great superficial petrosal branch ; 9, its great deep petrosal branch ; 10, a part of the sixth nerve, receiving twigs from the carotid plexus of the sympathetic ; 11, superior cervical sympathetic ganglion ; 12, its ascending branch ; 13, facial nerve; 14, glosso-pharyngeal nerve ; 15, its tympanic branch ; 16, carotico-tympanic twig joining the sympathetic ; 17, filament to the fenestra rotunda ; 18, filament to the Eustachian tube ; 19, filament to the fenestra ovalis ; 20, small superficial petrosal nerve. The posterior superior dental nerve arises from the superior maxillary trunk before it enters the infraorbital groove, and immediately divides into two branches (often separate at their origin), which descend with the posterior dental artery on the zygomatic surface of the upper jaw. They send small external filaments to the gum and the adjacent part of the mucous membrane of the cheek, and then enter the posterior dental canals to terminate in offsets to the molar teeth and the lining membrane of the antrum. Variety. — The posterior dental nerve has been seen in a few instances of large size, and replacing the buccal nerve, which was absent as a branch of the inferior maxillary, in the supply of the cheek. THE SUPERIOR MAXILLARY NERVE. The middle superior dental nerve leaves the superior maxillary in the hinder part of the infraorbital canal, and is directed downwards and forwards in a special canal in the outer wall of the antrum to the bicuspid teeth. The anterior superior dental nerve is the largest of the three. Arising near the infraorbital foramen, it descends in its canal in the front wall of the antrum, and divides into dental branches for the incisor and canine teeth, and a nasal branch, which supplies the pituitary membrane in the fore part of the inferior meatus and the adjoining part of the floor of the nasal fossa. The three dental nerves communicate so as to form loops with one another while they are contained in their bony canals, and from these loops other branches spring, which join again and give rise to a plexus (superior dental plexus) from which the minute terminal filaments proceed to the teeth and gum. Facial branches. — The facial branches are divisible into palpebral, nasal, and labial sets. The inferior palpebral branches, generally an inner and an outer, ascend from the termination of the infraorbital nerve to supply the skin and conjunctiva of the lower eyelid in its whole breadth. The lateral nasal branches, two or three in number, are directed inwards between the fibres of the levator labii superioris alaeque nasi muscle to the skin of the side of the nose. The superior labial branches, the largest of the terminal offsets of the superior maxillary nerve, and three or four in number, pass downwards between the elevator muscles of the upper lip and of the angle of the mouth. Ramifying as they descend, and giving off branches to supply the integument of the fore part of the cheek, they end in the skin and mucous membrane of the upper lip. Below the orbit, the terminal branches of the superior maxillary nerve are joined by considerable branches of the facial nerve, the union between the two being named the infraorbital plexus. Spheno-Falatiue Ganglion. The spheno-palatine ganglion, also named MeckeVs or the nasal ganglion, is deeply placed in the spheno-maxillary fossa, close to the spheno-palatine foramen. It receives the two spheno-palatine branches which descend together from the superior maxillary nerve as it crosses the top of the fossa. It is of a reddish-grey colour, triangular in form, and convex on the outer surface, and measures from before back about 5 mm. The grey or ganglionic substance contains multipolar nerve-cells, and does not involve all the fibres of the spheno-palatine branches of the upper maxillary nerve, but is placed at the back part, at the point of junction of the Vidian nerve, so that many of the fibres of the spheno-palatine nerves proceeding to the nose and palate pass to their destination without being incorporated with the ganglionic mass. Branches proceed from the ganglion upwards to the orbit, downwards to the palate, inwards to the nose, and backwards through the Yidian and pterygo-palatine canals. ASCENDING BRANCHES. — These are two or three very small twigs, which reach the orbit by the spheno-maxillary fissure, and are distributed to the periosteum and, according to Luschka, to the mucous membrane of the posterior ethmoidal and sphenoidal sinuses. Bock and Valentin describe a branch ascending- from the gang-lion to the sixth nerve ; Tiedemaim, one to the lower angie of the ciliary gang-lion. Hirzel and Arnold traced fila- ments to the optic nerve or its sheath. THE CRANIAL NERVES. DESCENDING BRANCHES. — These are three in number — the large, the small, and the external palatine nerves, and are in great part continued directly from the spheno-palatine branches of the superior maxillary. (a) The large or anterior palatine nerve descends in the palato-maxillary canal, and divides in the roof of the mouth into branches which are received into grooves in the hard palate, and extend forwards nearly to the incisor teeth. In the mouth it supplies the inner side of the gum, the glands, and the mucous membrane of the hard palate, and joins in front with the naso-palatine nerve. While in its canal, the large palatine nerve gives off one or two inferior nasal branches, which supply ' the mucous membrane over the greater part of the inferior turbinate bone, together with the adjoining middle and inferior meatuses of the nose. (#) The small or posterior palatine nerve enters the lesser palatine canal, and is conducted to the soft palate, the tonsil, and the uvula. It has been thought to convey motor fibres from the facial nerve to the levator palati and azygos uvulas muscles. (c) The external palatine nerve, the smallest of the series, courses through the external palatine canal between the maxilla and the tuberosity of the palate bone, Fig. 160. — XERVES OF THE NOSE AND THE SPHEXO-PALATIXE GANGLION FROM THE INNER SIDE. (From Sappey, after Hirschfeld and Leveille. ) 3 1, network of the external branches of the olfactory nerve : the area of distribution is repre- sented somewhat too large ; 2, nasal nerve, giving its external branch to the outer wall of the nose ; the septal branch is cut short ; 3, spheno-palatine ganglion ; 4. ramification of the large pala- tine nerve ; 5, small, and 6, ex- ternal palatine nerve : 7, inferior nasal branch ; 8, superior nasal branch ; 9, naso-palatine nerve cut short ; 10, Vidian nerve ; 11. great superficial petrosal nerve ; 12, great deep petrosal nerve ; 13, the sympathetic nerves ascending on the internal carotid artery. to be distributed to the tonsil and the outer part of the soft palate. This nerve is occasionally wanting. INTERNAL BRANCHES. — These consist of the naso-palatine, and the upper nasal branches, which ramify in the lining membrane of the nasal fossae and adjoining sinuses. The upper nasal are very small branches, and enter the back part of the nasal fossa by the spheno-palatine foramen. Some are prolonged to the upper and pos- terior part of the septum, and the remainder ramify in the membrane covering the upper two spongy bones, and in that lining the posterior ethmoidal cells. The naso-palatine nerve (fig. 144, 3), long and slender, leaves the inner side of the ganglion with the preceding branches, and after crossing the roof of the nasal fossa is directed downwards and forwards, in a slight groove on the vomer, towards the anterior palatine canal. The nerves of opposite sides descend to the palate through the median subdivisions of the canal, called the foramina of Scarpa, the nerve of the right side usually behind that of the left (see Osteology, p. 53). In the lower common foramen the two naso-palatine nerves are connected with each other in a fine plexus ; and they end in several filaments, which are distributed to THE SPHENO-PALATINE GANGLION. 243 the mucous membrane behind the incisor teeth, and communicate with the great palatine nerve. In its course along the septum, small filaments are furnished from the naso-palatine nerve to the pituitary membrane. POSTERIOR BRANCHES. — The branches directed backwards from the spheno- palatine ganglion are the Vidian and pharyngeal nerves. The Vidian nerve, arising from the back part of the ganglion, which seems to be prolonged into it, passes backwards through the Vidian canal to the foramen lacerum, where it divides into thQ great superficial and the great deep petrosal nerves. While in its canal, the Vidian nerve gives some small nasal branches, which supply the membrane of the back part of the roof of the nose and septum, as well as the mem- brane covering the end of the Eusbachian tube ; and it is joined by the sphenoidal filament from the otic ganglion (p. 249). The large superficial petrosal nerve (fig. 159,8), entering the cranium on the outer side of the carotid artery and beneath the Gasserian ganglion, is directed backwards in a groove on the petrous portion of the temporal bone to the hiatus Fallopii, and is thus conducted to the aqueductus Fallopii, where it joins the geniculate ganglion of the facial nerve. The large deep petrdsal nerve (fig. 159, 9), shorter than the other, is of a reddish colour and softer texture : it is directed backwards, and on the outer side of the carotid artery ends in the filaments of the sympathetic surrounding that vessel. In accordance with the view taken of the ganglia connected with the fifth nerve (p. 237), the superficial and deep petrosal parts of the Vidian nerve may be regarded as the motor and sympathetic roots respectively of the spheno-palatine ganglion, the spheno-palatine nerves constituting its sensory root. The ganglion may also receive fibres from the glosso-pharyngeal uerve, conveyed to it through the small and large deep petrosal nerves (p. 260, and fig. 170) : this connection is sometimes described as a second sensory root. The pharyngeal nerve is small, and springs from the back of the ganglion, often in common with the Vidian nerve. It enters the pterygo-palatine canal with an artery, and is lost in the lining membrane of the pharynx behind the Eustachian tube. SUMMARY. — The superior maxillary nerve, with Meckel's ganglion, supplies the integument of the cheek and the fore part of the temple, the lower eyelid, the side of the nose, and the upper lip ; the upper teeth ; the lining membrane of the nose ; the mucous membrane of the upper part of the pharynx, of the antrum of Highmore, and of the posterior ethmoidal cells ; the soft palate, tonsil, and uvula, and the glandular and mucous structures of the roof of the mouth. III.— INFERIOR MAXILLARY NERVE. The lower maxillary nerve (n. mandibularis), the third and largest division of the fifth, is made up of two portions of unequal size, the larger being derived from the Gasserian ganglion, and the smaller being the slender motor root of the fifth nerve. These two parts leave the skull by the foramen ovale in the sphenoid bone, and unite immediately after their exit. Three or four mm. below the base of the skull, and under cover of wthe external pterygoid muscle, the nerve separates into two primary divisions, one of which is higher in position and smaller than the other. The small, anterior, or upper portion (n. masticatorius) receives the greater part of the fibres of the motor root, and breaks up into temporal, masseteric, external pterygoid, and buccal branches, of which the last alone is a sensory nerve. The large, posterior, or lower portion is chiefly sensory, and divides into auriculo- temporal, lingual, and inferior dental nerves ; it likewise supplies through the last- 244 THE CRANIAL NERVES. mentioned branch the mylo-hyoid muscle and the anterior belly of the digastric. The branch to the internal pterygoid muscle, with which also are connected those proceeding through the otic ganglion to the tensors of the palate and tympanum, is sometimes counted as a part of the larger division, but is more correctly regarded as arising from the undivided trunk. The short trunk of the nerve also gives off, as it issues from the foramen ovale, a slender recurrent branch (n. spinosus), which passes backwards into the skull through the foramen spinosum with the middle meningeal artery, and divides like that vessel into two branches. The anterior of these sends its filaments into the Fig. 161. — PLAN OF THE INFERIOR. MAXILLARY NERVE. (GK D. T.) great wing of the sphenoid bone, while the posterior traverses the petro-squamous fissure, and is distributed to the mucous lining of the mastoid cells (Luschka). From the sheath which the inferior maxillary nerve receives from the dura mater in its passage through the foramen ovale tubular prolongations are continued on the several offsets of the trunk. Those containing the. masseteric and auriculo-temporal nerves are of consider- able strength, and become blended with the capsule of the temporo-maxillary articulation in front and on the inner side respectively, so that they are exposed to a certain degree of traction during the movements of the lower jaw. (E. Fawcett, Journ. Anat., xxvii, 1893, p. 179.) Varieties. — One or more of the branches of the superior division of the nerve may arise separately from the main trunk. There is not unfrequently a small fibrous band {pti>ry Area cribrosa superior. Cochlear nerve . Area cribrosa media. . Foramen singulare. ( Tractus spiralis foraminu- . < lentus and foramen cen- ( trale cochleae. IX.— GLOSSO-PHARYNGEAL NERVE. The ninth or glosso-pharyngeal nerve emerges from the upper part of the medulla oblongata, in the groove between the olivary and restiform bodies, by five Fig. 174. — PLAN OF THE ORIGIN OF THE GLOSSO-PHARYNGEAL NERVE. (After Obersteiner. ) The outline represents a transverse section of the upper end of the bulb : IX, roots of the glosso-pharyngeal nerve ; F.S. , funiculus solitarius ; N.IX, glosso-pharyngeal nucleus ; N.AM., nucleus ambiguus ; A.V, ascending or bulbar root of the fifth nerve. or six filaments arranged in a vertical line com- mencing immediately below the facial nerve. From this spot the rootlets of the nerve pass backwards and inwards through the bulb to the special nucleus beneath the inferior fovea in the floor of the fourth ventricle ; some of the fibres turn downwards into the funiculus solitarius, and others, probably efferent, bend forwards to the upper prolongation of the accessory vagal nucleus (nucleus ambiguus). The glosso-pharyngeal is composed almost entirely of very fine fibres, but mixed with these there are a few of medium size. From its superficial origin, the glosso-pharyngeal nerve is directed outwards in front of the flocculus to the middle compartment of the jugular foramen, through which it passes in company with the pneumo-gastric and spinal accessory nerves, but in a separate tube of dura mater. In the foramen, where it is placed external to and somewhat in front of the other nerves, it is lodged in a groove, occasionally a canal, in the lower border of the petrous portion of the temporal bone, and it pre- sents, successively, two ganglionic enlargements — the jugular ganglion and the petrosal ganglion, containing unipolar nerve-cells, like those of the spinal ganglia. After leaving the skull, the glosso-pharyngeal nerve appears between the internal carotid artery and the jugular vein, and is directed downwards over the carotid artery and beneath the styloid process and the muscles connected with it, to the hinder border of the stylo-pharyngeus ; then curving gradually forwards, it crosses THE GLOSSO-PHARYNGEAL NERVE. 259 over the outer surface of the latter muscle, and passes beneath the hyo-glossus to end in branches for the hinder part of the tongue (fig. 179, 16). The jugular ganglion (g. superius) is situated at the upper part of the osseous groove in which the nerve lies during its passage through the jugular foramen. It is Fig. 175. — DIAGRAMMATIC SKETCH FROM BEHIND OF THE ROOTS OF THE NINTH, TKNTH, AND ELEVENTH NERVES, WITH THEIR GANGLIA AND COMMUNICA- TIONS. (Bendz.) A, part of the cerebellum above the fourth ven- tricle ; B, medulla oblongata ; C, spinal cord; 1, glosso-pharyngeal nerve ; 2, pneumo-gastric ; 3, 3, 0, spinal accessory ; 4, jugular ganglion of the glosso-pharyngeal ; 5, petrosal ganglion ; 6, tym- panic branch ; 7, ganglion of the root of the pneumo-gastric ; 8, auricular branch ; 9, ganglion of the trunk of the pneumo-gastric ; 10, branch from the upper ganglion to the petrosal ganglion of the glosso-pharyngeal ; 11, inner portion of the spinal accessory ; 12, outer portion ; 13, pharyngeal branch of the pneumo-gastric ; 14, 14, superior laryngeal branch ; 15, twigs connected with the sympathetic ; 16, internal part of the spinal acces- sory prolonged with the pneumo-gastric. from 1 to 2 mm. in length, and it includes only the lower filaments of the nerve, the upper ones forming a separate fasciculus which passes over the ganglion, and joins the trunk of the nerve below it. This ganglion is not always to be distinguished, and it is regarded by Henle and others as Fig. 176. — THE TYMPANIC BRANCH OF THE GLOSSO- PHARYNGEAL NERVE, AND ITS CONNECTIONS. (Breschet.) A, squamous part of the left temporal bone ; B, petrous part ; C, inferior maxillary nerve ; D, internal carotid artery ; a, tensor tympani muscle : 1, sympathetic plexus ; 2, otic ganglion ; 3, glosso- pharyngeal nerve ; 4, tympanic nerve ; 5, 5, caro- tico-tympanic twigs ; 6, twig to fenestra rotunda ; 7, twig to fenestra ovalis ; 8, junction with the facial nerve ; 9, small superficial petrosal nerve ; 10, twig from the otic ganglion to the tensor tym- pani muscle ; 11, facial nerve ; 12, chorda tympani ; 13, petrosal ganglion of the glosso-pharyngeal ; 14, small deep petrosal nerve. resulting, when present, from the more or less complete separation of a part of the petrosal ganglion. The petrosal ganglion is contained in a small depression at the lower end of the groove in the petrous part of the temporal bone, and measures from 4 to 5 mm. in length. From it arise the small branches by which the glosso-pharyngeal is connected with other nerves at the base of the skull ; these are the tympanic nerve, and the branches of communication with the pneumo-gastric and sympathetic. BRANCHES. — A. Connecting branches and tympanic branch. One filament unites the petrosal ganglion of the glosso-pharyngeal nerve with the upper cervical ganglion of the sympathetic ; a second passes to the auricular 360 THE CRANIAL NERVES. branch of the pneumo-gastric ; and a third, which however is not constant, joins the ganglion of the root of the pneumo-gastric nerve. The glosso-pharyngeal nerve is also joined below the petrosal ganglion, in many cases, by a communicating branch from the facial nerve (p. 254). The tympanic branch (nerve of Jacobson) ascends from the petrosal ganglion, in company with the tympanic branch of the ascending pharyngeal artery, through a small canal, the orifice of which is seen on the ridge of bone between the jugular fossa and the carotid foramen. Having gained the inner wall of the tympanum, the nerve runs upwards and forwards in a groove on the surface of the promontory, and, after giving (or receiving) several branches, leaves the cavity at its upper and fore part, where it becomes the small superficial petrosal nerve. The latter traverses a small canal, which crosses beneath the upper end of the canal of the tensor tympani muscle, and emerges on the upper surface of the petrous portion of the temporal bone, immediately external to the hiatus Fallopii. Then inclining downwards, the Fig. 177. — THE TYMPANIC NERVE OF THE LEFT SIDE IN ITS CONNEC- TION WITH THE FACIAL. (KraUSC.) f 1, facial nerve, proximal end ; 2, geniculate ganglion ; 3, facial nerve, distal end ; 4, nerve to fenestra ovalis ; 5, ganglion-cells in tympanic nerve ; 6, nerve of fenestra rotunda ; 7, tympanic nerve from glosso-pharyngeal ; 8, small deep petrosal nerve ; 9, nerve to Eustachian tube ; 10, filament to geuiculate ganglion ; 11, small superficial petro- sal nerve ; 12, petrosal branch of middle meningeal artery ; 13, large superficial petrosal nerve ; 14, Pacinian corpuscles in the dura mater. nerve passes from the skull through the fissure between the petrous and the great wing of the sphenoid, or occasionally through a small aperture in the latter bone, and terminates in the otic ganglion. As it lies in its canal, the small superficial petrosal nerve is joined by a filament of communication from the geniculate ganglion of the facial nerve, or from the large superficial petrosal nerve close to that ganglion. The branches of the tympanic nerve are partly dis- tributed to the mucous lining of the middle ear, and partly form communications with other nerves, giving rise to what is called the tympanic plexus. Of the former set, the principal branches are — one directed forwards to the Eustachian tube, and two backwards to the neighbourhood of the fenestra rotunda and fenestra ovalis, and to the mastoid cells. The communicating branches are, in addition to the small superficial petrosal nerve with its filament of union with the facial, one or two twigs (carotico-tympanic) which pass downwards and forwards through the anterior wall of the tympanum to the carotid canal and join the sympathetic on the carotid artery, and the small deep petrosal nerve which runs forwards in a minute canal in the substance of the processus cochleariformis and enters the foramen lacerum, where it joins the carotid plexus of the sympathetic, or sometimes one of the large petrosal nerves (figs. 165, 170). The tympanic nerve while in its canal is surrounded by a small fusiform mass of soft vascular tissue which has been called the tympanic gland (Krause) ; and as it lies in the tympanum it contains numerous nerve-cells in irregular groups. B. Branches distributed in the neck. Pharyngeal branches. — The largest of these (carotid branch, pharyngeal division of the glosso-pharyngeal nerve — Henle) descends along the internal carotid THE GLOSSOPHARYNGEAL KERVE. 261 artery and unites with the pharyngeal branch of the vagus to form the pharyngeal plexus (p. 2C5) ; this branch is sometimes divided into two or even three parts. One or two smaller twigs pass inwards through the superior constrictor muscle, and supply the mucous membrane of the upper part of the pharynx. A muscular branch is furnished to the stylo-pharyngeus, and sends also fila- ments through the muscle to the mucous membrane of the pharynx. Tonsillitic branches. — Slender filaments pass from the glosso -pharyngeal nerve, as it approaches the base of the tongue, to the tonsil, over which they form a sort of plexus (circulus tonsillaris), to the soft palate, and to the pillars of the fauces. Lingual branches. — The glosso-pharyngeal nerve divides as it passes beneath the hyo-glossus muscle into two parts. One turns to the upper surface of the tongue and subdivides into many branches, which supply the circumvallate papillae and the mucous membrane over the posterior third of the organ, the hindmost filaments reaching the anterior surface of the epiglottis. The other is smaller, and is distri- buted to the mucous membrane of the side of the tongue, extending to about the middle of its length, where it forms a communication with the lingual nerve. Beneath the mucous membrane the terminal filaments are united in a plexus which contains microscopic ganglia. Variety. — In one case a branch from the glosso-pharyngeal supplied the mylo-hyoid muscle and the anterior belly of the digastric, the normal mylo-hyoid nerve being wanting (Guy's Hosp. Reports, vol. xiv, p. 453). SUMMARY. — The glosso-pharyngeal nerve distributes branches to the mucous membrane of the tongue, pharynx and middle ear, as well as to the stylo-pharyngeus muscle, and possibly also to the middle constrictor of the pharynx. By its small superficial petrosal branch it furnishes secretory and vaso-dilator fibres (through the otic ganglion and the auriculo-temporal nerve) to the parotid gland. It is connected with the following nerves, viz., the inferior maxillary division of the fifth (through the otic ganglion), the facial, the pneumo-gastric (its trunk and branches), and the sympathetic. X.— PNEUMO-GASTRIC NERVE. The tenth or pneumo-gastric nerve (nervus vagus, par vagum) is much larger than the glosso-pharyngeal, and has the longest course of all the cranial nerves, extending through the neck and thorax to the upper part of the abdomen. It arises from the medulla oblongata immediately in front of the restiform body, by twelve or fifteen filaments beginning close below, and continuing the line of, the roots of the glosso-pharyngeal nerve. Its central connections are similar to those of the glosso- pharyngeal, the roots passing backwards towards the floor of the fourth ventricle, where the greater part of the fibres enter the vagal nucleus beneath the ala cinerea, while a smaller number pass into the funiculus solitarius, and a third set, believed to be efferent, spring from the accessory vagal nucleus. The fibres of the vagal roots are mostly small. In the trunk of the nerve there are also numerous fibres of medium size, but these are probably derived in large part from the bulbar portion of the spinal accessory nerve, which joins the vagus close below the skull. Many of the larger fibres are continued into the pharyngeal and inferior laryngeal branches, which are in great measure distributed to striped muscles. The roots of the vagus form at first a flat band, which is directed outwards below the flocculus to the middle compartment of the jugular foramen. Here the nerve is contained in the same sheath of dura mater and arachnoid as the spinal 262 THE CRANIAL NERVES. accessory nerve, and its filaments unite in a small gang-Home enlargement which is known as the ganglion of the root of the pneumo-gastric. After its passage through the foramen, it is joined by the accessory part of the spinal accessory nerve, and a second ganglion is formed upon it, the ganglion of the trunk of the nerve. Several communications are at the same time established with surrounding nerves. The upper ganglion or ganglion of the root of the pneumo-gastric nerve i ganglion jugular e), situated in the jugular foramen, is of a greyish colour, nearly spherical, and about 4 mm. in diameter. It has filaments connecting it with other nerves, viz., with the facial, the petrosal ganglion of the glosso-pharyngeal, the spinal accessory, and the sympathetic. The lower ganglion or ganglion of the trunk of the pneumo-gastric nerve (cervical ganglion, ganglion nodoswri) is placed below the base of the skull, about 1 cm. beyond the upper ganglion. It is of a flattened cylindrical form and reddish colour, and measures from 15 to 20 mm. in length and 4 in breadth. The nX't C.r. Fig. 178. — SECTION OF THE BULB AT ABOUT THE MIDDLE OP THE OLIVE. (Schwalbe. ) The full description of this figure will be found at p. 54 of parti. The following numbers refer to the vagus and hypoglossal nerves and their connections : n X, n X', two parts of the vagal nucleus; f.s., funiculus solitarius ; n. am, nucleus ambiguus or accessory vagal nucleus ; X, bundle of vagus emerging between the resti- form body and the olive ; n. XII, hypoglossal nucleus ; XII, bundle of hypoglossal nerve emerging between the olive and the pyramid. accessory part of the spinal accessory nerve runs over the surface of the ganglion, and is in part continued directly into the pharyngeal and superior laryngeal branches of the vagus ; some of the accessory fibres, however, become incorporated with the main trunk, and enter the inferior laryngeal and cardiac branches. The lower ganglion communicates with the hypoglossal, the spinal, and the sympathetic nerves. The nerve-cells in both ganglia of the vagus belong to the unipolar or spinal type. The pneumo-gastric nerve descends in the neck between, and concealed by, the internal jugular vein and the internal carotid artery, and afterwards similarly between the vein and the common carotid artery, being enclosed along with them in the sheath of the vessels. In their passage into and through the thorax, the nerves are disposed differently on the right and left sides. On the right side the nerve crosses over the first part of the right subclavian artery at the root of the neck, and its recurrent laryngeal branch turns backwards and upwards round that vessel. The nerve then enters the thorax behind the right innominate vein, and descends on the side of the trachea to the back of the root of the lung, where it spreads out in the posterior pulmonary plexus. It emerges from this plexus in the form of two cords, which are directed to the oesophagus, and by their union and subdivision on it form, with similar branches of the left nerve, the oesophageal plexus. Xear the lower part of the thorax, the branches of the nerve, which have thus interchanged fibres writh the nerve of the left side, are gathered THE PNEUMO-GASTRIC NERVE. 263 again into a single trunk, which, descending through the diaphragm along the back of the oesophagus, is finally divided between the posterior surface of the stomach and the solar plexus. On the left side the pneumo-gastric nerve, entering the thorax between the left carotid and subclavian arteries and behind the left innominate vein, crosses over the Fig. 179. — THE DISTRIBUTION AND CONNECTIONS OF THE PNEUMO-GASTRIC NERVE ON THE LEFT SIDE IN THE NECK AND UPPER PART OF THE THORAX. (From Sappey, after Hirschfeld and Leveille".) £ 1, pneumo-gastric nerve ; 2, ganglion of its trunk ; 3, accessory part of the spinal accessory ; 4, union of the pneumo-gastric with the hypoglossal ; 5, pharyngeal branch of the pneumo-gastric ; 6, superior laryngeal nerve ; 7, external laryngeal ; 8, communication of the external laryngeal nerve with the superior cardiac branch of the sympathetic ; 9, inferior or recurrent laryngeal ; 10, superior, and 11, inferior cervical cardiac branches ; 12, 13, posterior pulmonary plexus ; 11, lingual branch of the inferior maxillary nerve ; 15, distal part of the hypoglossal nerve ; 16, glosso-pharyngeal nerve ; 17, spinal acces- sory nerve, uniting by its inner branch with the pneumo-gastric, and by its outer passing into the sterno- mastoid muscle ; 18, second cervical nerve ; 19, third ; 20, fourth; 21, origin of the phrenic nerve ; 22, 23, fifth, sixth, seventh, and eighth cervical nerves, forming with the first dorsal the brachial plexus ; 24, superior cervical ganglion of the sympathetic ; 25, middle cervical ganglion ; 26, inferior cervical ganglion united with the first dorsal ganglion ; 27, 28, 29, 30, second, third, fourth, and fifth dorsal ganglia. arch of the aorta, below which its recurrent laryngeal branch turns inwards and up- wards. It then passes behind the root of the left lung, forming, like its fellow, a 264. THE CRANIAL NERVES. posterior pulmonary plexus, whence it descends along the oesophagus, and takes part in the formation of the oesophageal plexus. Inferiorly, it forms a single trunk in front of the oesophagus, and is spread out on the anterior surface of the stomach. There are various circumstances in the distribution of the pneumo-gastric nerves which at first sight appear anomalous, but which are explained by reference to the process of develop- ment. The recurrent direction of the inferior laryngeal branches arises from the extreme shortness or rather absence of the neck in the embryo at first, and from the primitive arterial arches having- originally occupied a position at a higher level than the parts in which those branches are ultimately distributed, and having dragged them down as it were in the descent of the heart from the neck to the thorax. The recurrent direction may therefore be accepted as evidence of the development of those nerves before the occurrence of that descent. The passage of one recurrent laryngeal nerve round the subclavian artery, and of the other round the aorta, arises from the originally symmetrical disposition in which the innominate and sub- clavian arteries on the right side, a,nd the arch of the aorta on the left, are derived from cor- responding arches. The supply of the back of the stomach by the right pneumo-gastric nerve, and of the front by the left nerve, is connected with the originally symmetrical condition of the alimentary canal, and the turning over of the stomach on its right side in its subsequent growth. BRANCHES. — Some of the branches of the pneumo-gastric serve to connect this with other nerves, but the larger number are distributed to various parts of the cir- Fig. 180. — DIAGRAM OF THE ROOTS AND COMMUNI- CATING BRANCHES OP THE PNEUMO-GASTRIC AND NEIGHBOURING NERVES. (From Sappey, after Hirschfeld and Leveille.) 1, facial nerve ; 2, glosso-pharyngeal with the petrosal ganglion ; 2', connection of the digastric branch of the facial nerve with the glosso-pharyngeal nerve ; 3, pneumo- gastric, with its two ganglia ; 4, spinal accessory ; 5, hypoglossal ; 6, superior cervical ganglion of sympathetic ; 7, 7, loop of union between the first two cervical nerves ; 8, carotid branch of sympathetic ; 9, nerve of Jacobson (tym- panic), given off from the petrosal ganglion ; 10, its cavotico-tympanic filaments ; 11, twig to Eusta- chian tube ; 12, twig to fenestva ovalis ; 13, twig to fenestra rotunda ; 14, small supei'ficial petrosal nerve ; 15, large superficial petrosal nerve ; 1(5, otic ganglion ; 17, auricular branch of pneumo-gastric ; 18, connection of spinal accessory with pneumo- gastric ; 19, union of hypoglossal with first cervical nerve ; 20, union between the sterno-mastoid branch of the spinal accessory and that of the second cervical nerve ; 21, pharyngeal plexus ; 22, superior laryngeal nerve ; 23, external laryngeal ; 24, middle cervical ganglion of sympathetic. culatory, respiratory and digestive systems. The special connecting branches arise from the two ganglia of the nerve. The branches of distribution arise from the nerve in the several stages of its course as follows : — In the jugular foramen, one small branch is given to the dura mater, and another to the ear ; in the neck, branches are furnished successively to the pharynx, the larynx, and the heart ; in the thorax, additional branches are supplied to the heart, as well as offsets to the peri- cardium, lungs and oesophagus ; and in the abdomen, its terminal branches are dis- tributed to the stomach, liver, and other organs. A. Branches of communication. The upper ganglion of the pneumo-gastric nerve receives a twig from the superior cervical ganglion of the sympathetic ; one or two filaments pass between it THE PNEUMO-GASTKIC NERVE. 265 and the spinal accessory nerve ; and there is sometimes a filament connecting it with the petrosal ganglion of the glosso-pharyngeal. The lower ganglion of the pneumo-gastric forms connections with the hypo- glossal nerve, with the superior cervical ganglion of the sympathetic, and with the loop between the first two cervical nerves. B. Branches of distribution. The recurrent or meningeal branch, arises from the upper ganglion of the pneumo-gastric, and passes backwards through the jugular foramen to be distributed to the dura mater in the posterior fossa of the base of the skull. The auricular branch (nerve of Arnold) is given off from the ganglion of the root, and, after receiving a filament from the petrosal ganglion of the glosso-pharyn- geal nerve, runs backwards along the outer boundary of the jugular foramen to an opening near the root of the styloid process. It then traverses the substance of the temporal bone, crosses the acqueduct of Fallopiuson its inner side about 4 mm. from the lower end, forming here a communication with the facial nerve, and finally emerges between the external auditory meatus and the mastoid process, where it divides into two parts, the one of which joins the posterior auricular nerve, while the other is distributed to the skin of the back of the pinna, and the lower and back part of the auditory canal. Varieties. — In rare instances, absence of the auricular branch has been observed, or of the communication with the facial nerve. The auricular branch occasionally passes entirely into the facial trunk, and in that case its fibres are probably conveyed to the external ear through the posterior auricular nerve. The pharyngeal branch, often represented by two or even more offsets, and composed mainly of fibres prolonged from the accessory part of the spinal accessory nerve, leaves the upper part of the ganglion of the trunk of the vagus. It courses inwards over the internal carotid artery, and divides into branches which, conjointly with those derived from the glosso-pharyngeal and the sympathetic, form the pharyngeal plexus. This plexus often contains one or more small ganglia, and from it filaments pass to the muscles and mucous mem- brane of the pharynx. The motor fibres are conveyed to the plexus by the pharyn- geal branch of the vagus, but they are probably derived from the bulbar part of the spinal accessory nerve (see p. 270) ; the levator palati and azygos uvulae muscles are also supplied by a branch from this source.1 One slender branch (lingual branch of the vagus — Luschka) descends from the pharyngeal plexus, receiving its fibres from the pharyngeal branches of both the glosso-pharyngeal and pneumo-gastric nerves, and joins the hypoglossal nerve as that turns round the occipital artery. Superior laryngeal nerve. — This branch springs from the middle of the ganglion of the trunk of the vagus, and inclines forwards on the inner side of the internal carotid artery towards the larynx. It is joined by filaments from the upper cervical ganglion of the sympathetic and from the pharyngeal plexus, and speedily divides into two branches which are distinguished as external and internal laryngeal. The external laryngeal branch, the smaller of the two, runs downwards and for- wards beneath the depressor muscles of the hyoid bone to the crico-thyroid muscle in which it ends. It receives a filament from the upper cervical ganglion of the sympathetic, and it gives off twigs to the inferior constrictor muscle of the pharynx, as well as generally a cardiac branch which joins the superior cardiac branch of the sympathetic. The internal laryngeal branch is continued to the interval between the hyoid 1 The middle constrictor of the pharynx would appear in the monkey to be partly supplied by glosso- pharyngeal fibres (Beevor & Horsley, op. cit. on p. 270). £66 THE CRANIAL NERVES. bone and the thyroid cartilage, where it perforates the thyro-hyoid membrane with the laryngeal branch of the superior thyroid artery, and breaks up into numerous diverging branches which supply the mucous membrane of the greater part of the larynx. Some of these ascend in the ary-epi glottic fold to the base of the tongue and the epiglottis ; while others pass downwards to the false vocal cord, and also to the part of the pharyngeal mucous membrane covering the back of the larynx. One long branch descends beneath the ala of the thyroid cartilage, and joins at the lower part of the larynx a similar offset ascending from the recurrent laryngeal nerve. Varieties. — The superior laryngeal nerre may pass on the outer side of the internal carotid artery. The external laryngeal branch often arises separately from the main trunk. Offsets of the external laryngeal nerve have been described by different anatomists as passing to the pharyngeal plexus, to the thyroid body, to the sterno-hyoid, sterno-thyroid, and thyro-hyoid muscles, to the lateral crico-arytenoid muscle, and to the mucous membrane of the true vocal cord and lower part of the larynx. The internal laryngeal IrancJi has been seen piercing the thyroid cartilage. A middle laryngeal nerve is described by S. Exner as a slender offset from the pharyn- geal plexus (in the rabbit and dog directly from the pharyngeal branch of the vagus), which is distributed to the crico-thyroid muscle, and to the mucous membrane of the lower part of the larynx by means of twigs which perforate the crico-thyroid membrane. (i; Die Innervation des Kehlkopfes." Wiener Sitzungsber., 1884.) Inferior laryngeal nerve. — The inferior or recurrent laryngeal nerve of the right side arises at the root of the neck, and turns backwards below the subclavian Fig. 181. — VlEW OF THE DISTRIBUTION AND CONNECTIONS OF THE PNEUMO-GASTRIC AND SYMPATHETIC NERVES ON THE RIGHT SIDE. (Hirschfekl and Leveille. ) a, lachrymal gland ; 6, sublingual gland ; c, submaxillary gland and facial artery ; d, thyroid body ; c, trachea, below which is the right bronchus cut across ; /, resophagus ; g, stomach, divided near the pylorus ; i. transverse colon ; r, the diaphragm. A, heart ; B, aorta, drawn forwards to show the cardiac plexus ; C, innominate artery ; D, subcla- vian ; E, inferior thyroid ; F, a detached part of the external carotid, upon which runs a nervous plexus ; G, internal carotid emerging from its canal superiorly ; H, descending thoracic aorta ; K, intercostal vein ; L, pulmonary artery ; M, superior vena cava ; 0, intercostal artery. 1, ciliary nerves ; 2, branch of third nerve to inferior oblique muscle ; 3, 3, 3, the three divisions of the fifth nerve ; 4, ciliary ganglion ; 5, spheno-palatine ; 6, otic ; 7, submaxillary ; 8, sublingual ; 9, sixth nerve ; 10, facial in its canal, uniting with the spheno-palatine and otic ganglia ; 11, glosso-pharyngeal ; 12, right pneumo-gastric ; 13, left pneumo-gastric spreading on the anterior surface of the stomach ; 14, spinal accessory ; 15, hypoglossal ; 16, 16, nerves of cervical plexus ; 17, middle trunk of brachial plexus ; 18, intercostal nerve ; 19, lumbar nerve ; 21, superior cervical ganglion ; 22, tympanic nerve ; 23, large superficial petrosal nerve ; 24, cavernous plexus ; 25, sympathetic root of ciliary ganglion ; 26, fila- ment to pituitary body ; 27, union of sympathetic with upper cervical nerves ; 28, pneumo-gastric nerve ; 29, superior laryngeal nerve ; 30, pharyngeal plexus ; 31, cord of sympathetic ; 32, superior cardiac nerve ; 33, middle cervical ganglion ; 34, twig connecting the ganglion with, 35, the recurrent ; 36, middle cardiac nerve ; 37, cord of sympathetic ; 38, inferior cervical ganglion ; 39, the line from this number crosses the nerves proceeding from the brachial plexus ; 40, sympathetic twigs surrounding the axillary artery ; 41, branch of union with the first intercostal nerve ; the line from the letter e, pointing to the trachea, crosses the superior, middle, and inferior cardiac nerves ; 42, cardiac plexus ; 43, 44, right and left coronary plexuses ; 45, 46, thoracic portion of the sympathetic cord ; 47, great splanchnic nerve ; 48, semilunar ganglion ; 49, lesser splanchnic ; 50, solar plexus ; 51, union with the pneumo- gastric rerve ; 52, diaphragmatic plexus ; 53, gastric plexus ; 54, hepatic ; 55, splenic ; 56, superior mesenteric ; 57, renal plexus ; 58, first lumbar sympathetic ganglion. artery ; the nerve of the left side arises in the upper part of the thorax, and is re- flected round the arch of the aorta immediately beyond the attachment of the liga- mentum arteriosum. Each nerve ascends in the neck behind the common carotid artery, crossing either in front of or behind the inferior thyroid artery (see Yol. II, p. 424), and lying in the groove between the trachea and oesophagus, to the lower border of the cricoid cartilage, where it enters the larynx beneath the inferior con- strictor muscle. Under cover of the ala of the thyroid cartilage, the nerve divides into branches which supply all the intrinsic muscles of the larynx, with the exception of the crico-thyroid. It likewise gives a few offsets to the mucous membrane below THE PNEUMO-GASTRIC NERVE. 267 Fig. 181 268 THE CRANIAL NERVES. the rima glottidis, and a connecting filament which joins the long branch of the upper laryngeal nerve beneath the hinder part of the thyroid cartilage : through this communication sensory fibres are probably conveyed to the inferior laryngeal nerve.1 The recurrent nei've also furnishes branches to the cardiac plexus, and twigs of communication with the inferior cervical ganglion of the sympathetic, as it turns round the large artery ; tracheal and oesophageal branches as it ascends in the neck ; and lastly, offsets to the inferior constrictor of the pharynx as it passes beneath that muscle. Varieties. — In cases of dorsal origin of the right subclavian artery the inferior laryn- geal nerve does not turn round that vessel, but passes inwards more directly to the larynx (see Vol. II, p. 386). This nerve has been seen furnishing twigs to the crico-thyroid muscle. Cardiac branches. — Branches to the heart are given off by the pneumo-gastric nerve both in the neck and in the thorax. The cervical cardiac branches arise at both the upper and the lower part of the neck. The upper branches, one or t\vo, are small, and join the cardiac nerves of the sympathetic. The lower, a single branch, arises as the pneumo-gastric nerve is about to enter the chest. On. the right side this branch lies by the side of the innominate artery, and joins one of the cardiac nerves destined for the deep cardiac plexus : it gives some filaments to the coats of the aorta. The branch of the left side crosses the arch of the aorta, and ends in the superficial cardiac plexus. The thoracic cardiac branches of the right side leave the trunk of the pneumo- gastric as this nerve lies by the side of the trachea, and some are also derived from the first part of the recurrent branch ; they pass inwards on the air-tube, and end in the deep cardiac plexus. The corresponding branches of the left side usually come entirely from the recurrent laryngeal nerve. The depressor nerve of the rabbit would appear to be represented in man in many cases by a slender branch which arises from the vagus in common with or just below the superior laryn- geal nerve, or perhaps has a double origin, and either descends to the cardiac plexus in con- junction with the superior cardiac nerve of the sympathetic (seldom independently), or rejoins the vagus trunk from 1 to 3 cm. below its origin. In cases where this branch is not to be re- cognised the fibres are probably contained in the vagus trunk as far as the lower part of the neck. It is thought by Finkelstein and Alpiger that depressor fibres run in the cardiac offset of the external laryngeal nerve. (A. Kreidmann, i; Anatomische Untersuchungen liber den Nervus depressor beim Menschen und Hunde," Arch. f. Anat.. 1878 ; A. Finkelstein. " Der Nervus depressor beim Menschen. Kaninchen, Hunde," &c., Arch. f. Anat., 1880 ; A. Viti. '• Re- cherches de morphologic sur le nerf depresseur chez 1'homme et chez les autres mammiferes," Arch. ital. de Biol., v, 1884 ; G. Bekesy. " Beitrage zur Anatomie der Herznerven," 1888 ; M. Alpiger, '; Anatomische Studie liber das gegenseitige Verhalten der Vagus- und Sympathi- cusaste im G-ebiete des Kehlkopfes," Langenbeck's Archiv, xl, 1890.) Pulmonary branches. — Two sets of pulmonary branches are distributed from the pneumo-gastric nerve to the lung ; and they reach the root of the lung, one on its fore part, the other on its posterior aspect. The anterior pulmonary nerves, two or three in number, are of small size. They join with filaments of the sympathetic ramifying on the pulmonary artery, and with these nerves constitute the anterior pulmonary plexus. Behind the root of the lung the pneumo-gastric nerve becomes flattened, and gives several branches of much larger size than the anterior branches, which, with filaments derived from the second, third, and fourth thoracic ganglia of the sympathetic, form the posterior pulmonary plexus. Offsets from this plexus 1 Howell and Huber, " Physiology of the communicating branch between the superior and the inferior laryngeal nerves," Journ. of Physiology, xii, 1891. THE PNEUMO-GASTBIC NERVE. £69 extend along the ramifications of the air-tube through the substance of the lung, where they are beset with minute ganglia. The anterior and posterior pulmonary plexuses of the two sides communicate with one another in an open network across the front and back respectively of the lower end of the trachea, and through these networks fibres are conveyed from both pneumo-gastric nerves into each lung. CEsophageal branches. — The oesophagus within the thorax receives branches from the pneumo-gastric nerves, both above and below the pulmonary branches. The lower branches are the larger, and are derived from the oesophageal plexus, formed by connecting cords between the nerves of the right and left sides, while they lie in contact with the oesophagus. Fericardial branches. — Either vagus may furnish a filament to the upper and fore part of the pericardium. Other twigs pass regularly to the back of the pericar- dium from the oesophageal plexus, and often from the posterior pulmonary plexuses (Zuckerkandl). Gastric branches. — The branches distributed to the stomach (gastric nerves} are terminal branches of both pneumo-gastric nerves. The nerve of the left side, on arriving in front of the oesophagus, opposite the cardiac orifice of the stomach, divides into many branches : the largest of these extend over the fore part of the stomach ; others lie along its small curvature, and unite with branches of the right nerve and the gastric plexus of the sympathetic ; and some filaments are continued between the layers of the small omentum to the hepatic plexus. The right pneumo- gastric nerve descends on the back of the gullet to the stomach, and distributes branches to the posterior surface of the organ : a large portion of this nerve passes to the solar, splenic and left renal plexuses of the sympathetic. SUMMARY. — The pneumo-gastric nerves convey motor fibres to the voluntary muscles of the soft palate (with the exception of the tensor palati), pharynx and larynx, these being in part at least derived originally from the spinal accessory, to the unstriped muscle of the alimentary canal — oesophagus, stomach and intestine (with the exception of the rectum), and of the air-passages — trachea, bronchi, and their divisions in the lungs. Sensory fibres are furnished to the pharynx, oesophagus and stomach, to the larynx, trachea and bronchial ramifications, as well as to the dura mater, the external ear, and the pericardium. The vagi also supply nerves to the heart, both efferent (inhibitory — also received from the spinal accessory) and afferent (depressor), and possibly inhibitory dilator fibres to the vessels of the intes- tine. Lastly, pneumo-gastric fibres pass, either directly or through the solar plexus and its offsets, to the liver, pancreas, spleen, kidneys and suprarenal bodies. Each pneumo-gastric nerve is connected with the following cranial nerves — the spinal accessory, glosso-pharyngeal, facial, and hypoglossal ; also with some spinal nerves ; and with the sympathetic in the neck, thorax and abdomen. XI.— SPINAL ACCESSORY NERVE. The eleventh or spinal accessory nerve (spinal nerve accessory to the vagus) con- sists of two parts, the one of which (bulbar or accessory) joins the trunk of the pneumo-gastric, while the other (spinal) is distributed to the sterno-mastoid and tra- pezius muscles. Its fibres spring from a continuous column of cells extending from the level of the lower third of the olive to the fifth cervical nerve, in the bulb placed dorso-laterally to the hypoglossal nucleus, and in the spinal cord forming a part of the ventro-lateral group of the anterior horn. From this nucleus the fibres are directed at first dorsally for a short distance, and then turn outwards through the lateral region of the bulb or cord to emerge in a series of filaments from the side of the VOL. III. PT. 2. S 270 THE CRANIAL NERVES. medulla oblongata below the pneumo-gastric nerve, and from the lateral column of the spinal cord as low down as the fifth or sixth cervical nerve. The filaments arising from the medulla oblongata form the small bulbar portion of the nerve. The lowest spinal filaments are attached to the middle of the lateral column ; the highest ones arise close to the posterior nerve-roots, with the upper one or two of which they are frequently connected. According to Holl the association of the dorsal root of the first cervical nerve with the spinal accessory is only apparent, the two being merely bound together by connective tissue, and not interchanging any fibres. Kazzander found, however, in many cases a common origin of rootlets of the accessory and first cervical nerves, or a passage of filaments between the two, and less frequently a communication with the second cervical nerve. In one case also there was a small ganglion on the highest root of the bulbar portion of the spinal acces- sory nerve. (M. Holl, "Ueb. d. Nerv. accessorius Willisii." Arch. f. Anat., 1878; J. Kaz- zander. " Ueb. d. N. accessorius Willisii u. seine Beziehungen zu d. oberen Cervicalnerven," &c.r Arch. f. Anat., 1891.) In the bulbar portion of the eleventh nerve fine fibres predominate, although there are some of medium and large size. The spinal portion of the nerve consists almost wholly of large fibres, and fine fibres are absent. The bulbar portion is directed outwards with the pneumo-gastric nerve : the spinal part ascends between the ligamentum denticulatum and the posterior Fig. 182. — SECTION OF' UPPER END OF SPINAL CORD, SHOWING ORIGIN OF SPINAL ACCESSORY NERVE. (After Lockhart Clarke. ) /, anterior, fp, posterior median fissure ; p, end of decussation of pyramids ; Cla, GIp, anterior and posterior roots of first cervical nerve ; XI, root of spinal accessory nerve ; c, central canal. roots of the cervical nerves, passes into the skull through the foramen magnum, and immediately bends outwards to enter the middle compartment of the jugular foramen, where the nerve is contained in the same sheath of dura mater as the vagus (see Vol. II, fig. 182). In the foramen, the two parts of the nerve interchange fibres, and they are sometimes intimately united so as to form a single trunk for a short distance. The accessory part is also connected by one or two filaments with the ganglion of the root of the pneumo- gastric. Below the skull, the internal, bulbar, accessory or vagal portion passes over the surface of the lower ganglion of the vagus, and sends its fibres into the pharyngeal and superior laryngeal branches, and into the trunk of that nerve belcw the ganglion in the manner already described. The bulbar portion of the spinal accessory nerve contains the inhibitory fibres which pass by the vagus to the heart, and, as has been shown for the monkey by the experiments of Beevor and Horsley and of Rethi, the motor fibres of the levator palati and azygos uvulae, as well as, in part at least, of the constrictor muscles of the pharynx. It is generally stated also that the motor fibres of the laryngeal muscles are derived from the same source, but this view is not confirmed by recent observations of Grossmann, Gra bower and Navratil. (Beevor and Horsley, "Note on some of the Motor Functions of certain Cranial Nerves (V., VII., IX., X., XI., XII.), and of the three first Cervical Nerves, in the Monkey," Proc. Roy. Soc., 1888 ; L. Rethi, "Die Nervenwurzeln der Rachen- und Gaumenmuskeln," and "Der periphere Verlauf der motorischen Rachen- und Gaumennerven," Wiener Sitzungsber., 1892 and 1893 ; M. Grossmann, " Ueber die Athembewegungen des Kehlkopfes, II. Die Wurzelfasern der Kehlkopfn erven," Wiener Sitaungsber.. 1889 ; Grabower, "Das Wurzelgebiet der motorischen Kehlkopfnerven," Centralbl. f. Physiol., iii, 1890; E. v. Navratil. '• Thierversuche iiber die Kehlkopfinnervation und iibei den N. accessorius Willisii." Ungar. Arch. f. Med., ii, 1894.) THE HYPOGLOSSAL NERVE 271 The external or spinal portion (fig. 183, 5), after issuing from the jugular foramen, is directed backwards either across the front of or behind the internal jugular vein, and perforates the sterno-mastoid muscle, supplying this with branches, and joining amongst the fleshy fibres with the nerve furnished to the muscle from the cervical plexus. Descending in the next place obliquely across the posterior triangular space of the neck behind the sterno-mastoid, the nerve passes beneath the trapezius muscle. Here it forms a kind of plexus with branches of the third and fourth cervical nerves, and distributes filaments to the trapezius, which extend nearly to the lower border of the muscle. Varieties. — The lower limit of the origin of the spinal part of the nerve was found by Holl to range from the third to the seventh cervical nerve, but in the greater number of cases it corresponded to the fifth or sixth nerve. It was seen by Sommering opposite the first dorsal nerve. The spinal part of the nerve in one case pierced the dura mater below the first cervical nerve, and re-entered the spinal theca higher up (Holl). The external portion of the spinal accessory nerve sometimes passes beneath the sterno-mastoid without piercing the muscle. In one instance this nerve has been seen terminating- in the sterno-mastoid muscle, the trapezius being- supplied entirely by the third and fourth cervical nerves (Cumow). In rare cases it has been observed sending a branch to join the descending cervical nerve. XII.— HYPOGLOSSAL NERVE. The hypoglossal or twelfth cranial nerve arises from a nucleus placed ventro- laterally to the central canal in the lower part of the medulla oblongata, and extend- ing upwards beneath the trigonum hypoglossi of the fourth ventricle (fig. 178, n. xn). Thence the fibres pass obliquely forwards and outwards, between the anterior and lateral areas of the bulb, and form a series of from ten to fifteen fine roots which emerge along the groove separating the pyramid from the olivary body. The fila- ments are directed outwards above (or behind) the vertebral artery, and are usually collected into two bundles which perforate the dura mater separately opposite the anterior condylar foramen, and are united into a single trunk as they pass through that opening. As it leaves the anterior condylar foramen the nerve is very deeply placed on the inner side of the deep cervical vessels and the pneumo-gastric nerve. Winding round the lower ganglion of the last, to which it is closely bound by connective tissue, the hypoglossal nerve descends, inclining at the same time gradually forwards between the internal carotid artery and jugular vein, to the lower border of the digastric muscle. At this level it curves forwards round the commencement of the occipital artery, the sterno-mastoid branch of which turns downwards over the nerve, and is thence directed forwards above the hyoid bone to the under part of the tongue. In the latter part of its course, it passes beneath the tendon of the digastric, the lower end of the stylo-hyoid, and the mylo-hyoid muscles ; it crosses the external carotid and the lingual arteries ; and it rests upon the hyo-glossus muscle, being- accompanied by the ranine vein of the tongue. At the anterior border of the hyo- glossus it is connected with the lingual branch of the fifth nerve, and then penetrates the fibres of the genio-glossus muscle, dividing into branches which are distributed to the muscular substance of the tongue. BRANCHES. — While passing through the anterior condylar foramen, the hypoglossal nerve gives off one or two minute recurrent twigs which ramify in the dura mater around the foramen magnum, and in the diploe of the occipital bone. They were thought by Luschka to be formed by recurrent fibres derived from the lingual nerve, but it is possible that they consist of fibres which ascend from the communication with the first cervical nerve, or from the sympathetic (Rudinger). The branches arising from the nerve in the neck are partly filaments of communication with other S 2 THE CRANIAL SERVES. nerves, but mainly offsets of distribution to muscles connected with the hyoid bone and larynx, and to the muscles of the tongue. A. Branches of communication. - Close below the skull the hypoglossal nerve is united by a filament with the superior cervical ganglion of the sympathetic, by one or more twigs with the loop between the first and second cervical nerves, and with the ganglion of the trunk of the vagus by fibres which pass between the two nerves where they are in close connection with one another. As the nerve turns round the occipital artery, it is joined by the small lingual branch of the vagus (p. 265) ; and in the • submaxillary region, it is connected with Fig. 183. — VIEW OP THE DISTRIBUTION OP THE SPINAL ACCESSORY AND HYPOGLOSSAL NERVES. (From Sappey, after Hirschfeld and Leveille.) | 1, lingual nerve ; 2, pneumo-gastric nerve ; 3, superior laryngeal (represented too large) ; 4, external laryngeal branch ; 5, spinal accessory ; 6, second cervical ; 7, third ; 8, fourth ; 9, origin of phrenic nerve ; 10, nerve to subclavius ; 11, external anterior thoracic nerve : 12, hypoglossal nerve ; 13, descending cervical nerve ; 14, communicating cervical nerve ; 15, 16, 18, 19, branches from the plexiform union of these nerves to the sterno-hyoid, sterno-thyroid and omo-hyoid muscles ; 17, branch to the anterior belly of the omo-hyoid muscle ; 20, branch, to the thyro-hyoid muscle; 21, communicating twigs from the hypoglossal to the lingual nerve ; 22, terminal branches of the hypoglossal nerve. the lingual branch of the fifth nerve by one or two slender loops over the fore part of the hyo-glossus muscle. B. Branches of distribution* Vascular branches. — These are one or two slender twigs which leave '''the hypoglossal nerve close below the skull and pass to the mesial aspect of the internal THE HYPOGLOSSAL NERVE. 273 jugular vein, where they are often, joined by filaments from the superior cervical ganglion of the sympathetic (Luschka). The descending cervical nerve (r. descendens hypoylossi) consists mainly of fibres which pass to the hypoglossal from the first and second cervical nerves in the communication below the skull. Leaving the trunk as it turns round the occipital artery, or a little higher up, the descending nerve runs downwards on the surface of the common carotid artery, inclining gradually from the outer to the inner side, and Fig. 184. — PLAN OF THK CONNECTIONS OK THE HYPOGLOSSAL WITH THE CERVfCAL NERVES, AND THE FOR- MATION OF THE ANSA CERVICALIS. ( After Holl.) being placed generally within, but sometimes on the front of, the carotid sheath. After having given off a branch to the anterior belly of the omo- hyoid muscle, it joins about the middle of the neck in a loop (ansa cervicalis) with the communicating cervical branches from the second and third cervical nerves. The concavity of the loop is turned upwards, and the connection between the nerves is fre- quently effected by two or more interlacing filaments which form a small plexus. From this interlacement of the nerves, offsets are continued backwards to the posterior belly of the omo-hyoid, and downwards to the sterno-hyoid and sterno-thyroid muscles. Muscular branches. — The branch to the thyro-hyoid muscle is a separate twig also composed of fibres proceeding from the cervical nerves, and leaving the hypoglossal trunk as it approaches the hyoid bone. As it lies beneath the mylo-hyoid, the nerve gives offsets to the styloglossus, hyo- glossus and genio-hyoid muscles, and the terminal branches, penetrating the genio- glossus, supply that muscle and' the intrinsic muscles of the tongue. According to Holl the nerve to the genio-hyoid is of cervical origin. The fibres proceeding from the first and second cervical nerves do not become mingled with those of the hypoglossal trunk, but for the most part form a small cord which can be separated from the latter by removing the common sheath, and followed down into the descending1 cervical nerve. A minute funiculus runs proximally with the hypoglossal nerve, and others pass on the deep aspect of the trunk to the recti antici. The descending cervical nerve THE SPINAL NE LIVES. also contains fibres which pass upwards from the communicating branches and run peripherally to enter the nerves of the thyro-hyoid and genio-hyoid muscles. (See M. Holl. " Beobachtungen iiber die Anastomosen des Nervus hypoglossus," Zeitschr. f. Anat. u. Entw., 1876.) The spinal origin of the nerves of the infrahyoid muscles has also been demonstrated ex- perimentally in the monkey by Beevor and Horsley, who found that stimulation of the hypo- glossal roots within the skull produced no effect on these muscles, while they were called into action by stimulating the first and second cervical nerves. The sterno-hyoid and sterno -thyroid were supplied mainly from the first nerve, and the omo-hyoid from the second (<>/>. fit. on p. 270). The fibres of the hypoglossal nerve are of medium size, resembling in this respect those of the facial nerve, and being smaller than those of most of the motor nerves passing to voluntary muscles (Gaskell). Varieties. — In one instance, recorded by Riidinger, the hypoglossal nerve was found taking its superficial origin from the posterior surface of the medulla oblongata. The vertebral artery is not unfrequently found passing forwards between, very rarely above, the roots of the nerve. The right and left nerves are occasionally united by a cross branch or loop in the sub- stance of the genio-hyoid, or between that and the genio-glossus muscle. In rare cases, the twelfth nerve gives filaments to the mylo-hyoid, to the digastric, or to the stylo-hyoid muscle. The descending cervical nerve sometimes appears to be derived either altogether from the pneumo-gastric or from both the pneumo-gastric and hypoglossal nerves, but it can always be shown by dissection that these varieties of origin are only apparent, resulting from the tem- porary adhesion of the filaments of this branch to those of the pneumo-gastric. A filament is occasionally continued from the descending cervical nerve into the thorax, where it joins the phrenic or the cardiac nerves ; in the latter case it is probably composed of fibres from the vagus or the sympathetic, which have joined the hypoglossal or the descending nerve. This nerve has also been seen sending a branch to the sterno-mastoid muscle. In some animals the twelfth nerve possesses a posterior root furnished with a ganglion, like a spinal nerve. A similar condition has been met with in a few instances in man. SUMMARY. — The hypoglossal nerve proper supplies only the muscles of the tongue, with the exception of the palato-glossus and the pharyngeo-glossus. Fibres derived from- the first three cervical nerves, which are associated with the hypoglossal for a part of their course are distributed to the infrahyoid muscles and the genio-hyoid. Others of uncertain origin pass to the skull and dura mater, and to the internal jugular vein. The hypoglossal forms connections with the pneumo-gastric, lingual, upper three cervical nerves, and sympathetic. SPINAL NERVES. The spinal nerves are characterised by their origin from the spinal cord, and their direct transmission outwards from the spinal canal in the intervals between the vertebrae. There are, in all, thirty-one pairs of these nerves, and, according to the region in which they issue from the spinal canal, they are named cervical, dorsal or thoracic, lumbar, sacral, and coccygeal. By universal usage each pair of nerves in the dorsal, lumbar and sacral regions is named in correspondence with the vertebra below which it emerges. Of the eight pairs of nerves between the cranium and the first dorsal nerve, the uppermost is placed above the atlas, and the second and following nerves below the seven cervical vertebrae in succession. These eight pairs are usually reckoned as eight cervical nerves, but the first is also distinguished by the name of suboccipital nerve. The nerves of the thirty-first pair emerge from the lower end of the sacral canal, pass below the first vertebra of the coccyx, and are named coccygeal. Varieties. — The spinal nerves necessarily vary in number with any deviation from the usual number of the segments of the vertebral column. Sometimes an additional coccygeal nerve exists. Among seven cases which were examined by Schlemm two coccygeal nerves were found on each side in one instance, and on one side in another case. According to Rauber vestiges of these, and also of a third pair of coccygeal nerves, are normally present in the bundles of medullated fibres contained in the filum terminale (see Part I, p. 6). On the other hand, the coccygeal nerve often appears to be wanting, being united to the filum termi- nale (Rauber, Kadyi). ORIGIN OF THE SPINAL NERVES. 275 THE ROOTS OF THE SPINAL NERVES. Each spinal nerve springs from the spinal cord by two roots which approach one another as they quit the spinal canal, and join in the corresponding intervertebral Fig. 185. — DIAGRAMMATIC OUTLINE OP THE ROOTS AND FIRST PART OF THE SPINAL NERVES, TOGETHER WITH THE SYMPA- THETIC TRUNK OF ONE SIDE. (Allen Thomson.) £ The view is taken from before. In the upper part of the figure the pons Varolii and medulla oblongata are represented, and from V to XII, the roots of the several cranial nerves from the trifacial to the hypoglossal are indicated. On thf left side 0 1, is placed opposite the first cervical nerve ; and the numbers 2 to 8, following below indicate the corresponding cervical nerves ; Br, brachial plexus ; D 1 , is placed opposite the inter- costal part of the first dorsal nerve, and the numbers 2, to 12, following mark the corresponding dorsal nerves ; L 1, the first lumbar nerve, and the numbers 2, to 5, following the remaining lumbar nevves ; Cr, the anterior crural, and o, the obturator nerve ; S 1, the first sacral, and the following numbers 2, to 5, the remaining sacral nerves ; 6, the coccygeal nerve ; Sc, great sciatic nerve ; x x , the filum terminale of the cord. On the left side of the figure the following letters indicate parts of the sympathetic nerve, viz., a, the superior cervical ganglion communicating with the upper cervical spinal nerves and continued below into the sympathetic cord ; b, the middle cervical ganglion ; c, d, the lower cervical ganglion united with the first dorsal ; d', the eleventh dorsal ganglion ; from the sixth to the ninth dorsal ganglion the origins of the great splanchnic nerve are shown ; I, the highest lumbar ganglion ; s s, the upper sacral ganglion. In the whole extent of the sympathetic cord, the twigs of union with the spinal nerves are shown. foramen into a single cord ; and each cord so formed separates immediately into two divisions, one of which is destined for parts in front of the spine, the other for parts behind it. General arrangement. — The roots of the nerves arise on each side of the spinal cord by two nearly continuous series of filaments (flla radicu- laria), the anterior of which emerge from the antero-lateral column opposite the anterior cornu of the grey matter, while the posterior are attached in a narrower line along the postero-lateral sulcus of the cord. The filaments composing a single nerve-root vary in number from five to ten, and converge from above downwards as they pass from the cord to the dura mater, where each root enters a special aperture. The posterior roots of the nerves are dis- tinguished from the anterior roots by their greater size, which is due to their constituent filaments being both more numerous and individually larger than those of the anterior roots. Each posterior root is farther marked by a ganglion (interverte- bral or spinal), of a size proportionate to that of the nerve on which it is formed. The cells of these ganglia are unipolar, and give origin to the afferent fibres of the spinal nerves, both central and peripheral. •-•- s c 276 THE SPINAL NERVES. The ganglia are in general placed in the intervertebral foramina, immediately beyond the spots at which the roots perforate the dura mater lining the spinal canal. The first and second cervical nerves, however, which do not pass through inter- vertebral foramina, have their ganglia in the corresponding position as they lie over the neural arches of the vertebras. The ganglia of the sacral nerves are contained in the spinal canal, that of the last nerve being occasionally at some distance from the point at which the nerve issues. The ganglion of the coccygeal nerve is placed in the canal within the sac of the dura mater, and at a variable distance from the origin of the nerve. The filaments of the posterior root of the nerve are collected into two bundles as they approach the ganglion, and the inner extremity of the oval-shaped ganglion is usually bilobate, the lobes corresponding to the two bundles of filaments. The anterior roots of the spinal nerves are smaller than the posterior, and are devoid of ganglia, their fibres arising from the cells of the grey matter of the spinal Fig. 186. — DIFFERENT VIEWS OF A POR- TION OF THE SPINAL COUI) FROM THE CERVICAL REGION WITH THE ROOTS OF THE NERVES. Slightly enlarged. (Allen Thomson. ) In A, the anterior surface of the speci- men is shown, the anterior nerve-root of the right side being divided ; in B, a view of the right side is given ; in C, the upper surface is shown ; in D, the nerve- roots and ganglion are shown from below : 1, anterior median fissure ; 2, posterior median furrow and septum ; 3, origin of the anterior nerve- roots ; 4, postero- lateral groove, into which the filaments of the posterior root are seen to sink ; 5, anterior root passing over the ganglion ; 5', in A, the anterior root divided ; 6, posterior root, the fibres of which enter 6', the ganglion ; 7, the antei-ior, and 7', the posterior primary division of the nerve, each of which is seen in A and D to be derived in part from the anterior and in part from the posterior root. cord, and mainly from those of the anterior cornu. Their filaments also tend to be collected into two bundles near the intervertebral foramen. Both anterior and posterior roots of all the spinal nerves contain fibres of very various sizes — large, medium (10 /ti to 5 /z), and fine, but the proportion in which the different groups occur is not the same throughout. The anterior roots of the cervical, lumbar, and sacral nerves consist mainly of large and medium-sized fibres, fine fibres being present only in small number, generally not exceeding- one-sixth of the whole. Those of the dorsal nerves, however, as well as the coccygeal. show a preponderance of fine fibres, which are about three times as numerous as the larger ones. The finest fibres (2'6 p. and less) are abundant in the anterior roots of the dorsal nerves, but rare in the other regions, except in the last two sacral and the coccygeal nerves. In the posterior roots the small fibres are about equal in number to the medium-sized and large fibres together ; and. fibres of the largest size (above 20 /u). which are frequent in the anterior roots, are here scanty. (E. Siemerling, Neurol. Centralbl., 1886, and '• Anatomische Untersuchungen iiber die menschlichen Ruckenniarkswurzeln," Berlin, 1887.) Varieties. — The posterior root of the first cervical nerve is sometimes wanting (8 percent., Kazzander) ; or it may arise partly or wholly from, or in common with, the spinal accessory nerve (see p. 270). A defect in the roots of the thoracic nerves is said to be very common by Adamkiewicz. who found in sixteen spinal cords only three with the full number of thoracic roots ; in three there was absence of both anterior and posterior roots of one nerve, in three absence of a posterior root only, and in seven absence of one anterior root (Virchow's Archiv. Ixxxviii, 1882). Communications between the root-filaments (especially the posterior) of adjoining nerves are frequently met with. Small detached portions of the intervertebral ROOTS OF THE SPIXAL NERVES. 277 ganglia (fjanfjlici nlx-rrantin of Hyrbl) are sometimes found on the posterior roots of the upper cervical nerves. The ganglia of the lumbar and upper sacral nerves are often double, there being- a distinct swelling on each of the bundles of the posterior root. The ganglion of the suboccipital nerve may be situated within the dural sheath, or be wanting (9 per cent.r Kazzander). but in such cases there are probably nerve-cells interspersed in the posterior root. According to Rattone there are regularly scattered nerve-cells along the posterior roots of all the spinal nerves (Internat. Monatschr. f. Anat. u. Hist., i, 1884). Size. — The roots of the upper cervical nerves are smaller than those of the lower nerves, the first being much the smallest, and the sixth the largest. The posterior roots of these nerves, with the exception of the first in which the anterior root is larger than the posterior, exceed the anterior in size more than in the other spinal nerves, and they are likewise composed of filaments which are considerably larger than those of the anterior roots. The roots of the dorsal nerves, exception being made of the first, which resembles the lowest cervical nerves and is associated with them in a part of its distribution, are of small size, and vary but slightly, or not at all, from the second to the last. The filaments of both roots are thinly strewed over the spinal cord, and are slender, those of the posterior exceeding"] in thickness those of the anterior root in only a small degree. The roots of the lower lumbar, and of the upper sacral nerves, are the largest of all the spinal nerves ; those of the lowest sacral and of the coccygeal nerve are, on the other hand, the smallest. All these nerves are crowded together upon the lower end of the cord. Of these nerves the anterior roots are the smaller, but the disproportion between the anterior and posterior roots is not so great as in the cervical nerves. Length. — The place at which the roots of the upper cervical nerves are connected with the spinal cord being nearly opposite the foramina by which they respectively leave the canal, these roots are comparatively short. But the distance between the two points referred to is gradually augmented from nerve to nerve downwards, so that the place of origin of the lower cervical nerves is the depth of at least one vertebra, and that of the lower dorsal nerves about the depth of three vertebrse, above the foramina by which they respectively emerge from the canal. Moreover, as the spinal cord extends no farther than the first lumbar vertebra, the length of the roots of the lumbar, sacral and coccygeal nerves increases rapidly from nerve to nerve, and in each case may be estimated by the distance of the foramen of exit from the extremity of the cord. Owing to their length, and the appearance they present in connection with the spinal cord, the aggregation of the roots of the nerves last referred to has been named the cauda equina. A. diagram showing the level at which the several roots arise from the cord in relation to the spines of the vertebrae, as determined by R. W. Reid, is given on p. 4 of Part I. of this volume. The absolute length of certain of the nerve-roots in a subject of 18 years of age. whose spinal cord was 41 cm. long, is shown in the following table, taken from Testut : — RIGHT SIDE. LEFT SIDE. 3rd cervical nerve . 18 mm. ... 17 inm. 5th ,. „ . 25 , . . . 25 „ 1st dorsal nerve . 33 , . 32 „ 5th , . 47 . . 47 10th , » • . 68 , . 68 12th , »? . Ill . . 110 1st lun ibar nerve . . 114 , . 114 2nd , „ . 138 . . 134 3rd » . 151 . . 151 4th 163 164 6th > :> • .181 180 1st sacral nerve . 188 ., . . . 188 5th . 280 ,. . . . 280 278 THE SPINAL NERVES. Direction. — The first cervical nerve is directed horizontally outwards. The roots of the lower cervical and dorsal nerves at first descend over the spinal cord, held in contact with it by the arachnoid, till they arrive opposite the several intervertebral foramina, where they are directed horizontally outwards. The nerves of the cauda equina run in the direction of the spinal canal. Division of the nerves. — The two roots of each of the spinal nerves unite immediately beyond the ganglion, and the trunk thus formed separates, as already mentioned, into two divisions, an anterior or ventral and a posterior or dorsal, which are called primary branches or divisions, and each of which contains fibres proceeding from both the anterior and posterior roots. Fig. 187. — PLAN OP THE MODE OP BRANCHING OF A SPINAL NERVE. Before dividing in the manner above described each spinal nerve gives off a small recurrent or meningeal branch, which is joined by a filament from the com- municating cord between the anterior division of the nerve and the sympathetic, and then runs inwards through the intervertebral foramen to the spinal canal, where it is distributed to the vertebrae and ligaments, to the blood-vessels of the canal, and to the dura mater (Luschka, Riidinger). POSTERIOR PRIMARY DIVISIONS OP THE SPINAL NERVES. The posterior divisions of the spinal nerves are, with few exceptions, smaller than those given to the fore part of the body. Springing from the trunk which results from the union of the roots of the nerve in the intervertebral foramen, or frequently by separate fasciculi from the two roots, each turns backwards at once, and soon divides into two parts, distinguished as external and internal, distributed to the muscles and the integument behind the spine. The first cervical, the fourth and fifth sacral, and the coccygeal are the only nerves the posterior divisions of which do not separate into external and internal branches. SUBOCCIPITAL NERVE. — The posterior division of the first cervical or suboccipital nerve, slightly larger than the anterior, emerges over the arch of the atlas, between this and the vertebral artery, and enters the space bounded by the larger rectus and the two oblique muscles, where it divides into branches for the surrounding muscles. (a) One branch descends to the inferior oblique, and gives a filament, through or over the fibres of that muscle, to join the second cervical nerve. (£) Another ascends over the rectus posticus major muscle, supplying it and the smaller rectus. (c) A third enters the superior oblique muscle. (d) A fourth sinks into the complexus, where that muscle covers the nerve and its branches. Variety. — A cutaneous branch is occasionally given to the back of the head : it accompanies the occipital artery, and is connected beneath the integument with the great and small occipital nerves. POSTERIOR PRIMARY DIVISIONS. 279 Pig. 188. — SUPERFICIAL AND DEEP DISTRIBUTION OP THE POSTERIOR PRIMARY DIVISIONS OP THE SPINAL NERVES. (After Hirschfeld and Leveille. ) i On the left side the cutaneous branches are shown lying upon the superficial muscles; on the right side, these muscles having been removed, the splenius and complexus have been divided in the neck, and the erector spinse separated and partially removed in the back, so as to expose the deep portions of the nerves. a, a, small occipital nerve from the cervical plexus ; 1, muscular branches of the first cervical nerve and union by a loop with the second ; 2, placed on the rectus capitis posticus major, marks the great occipital nerve passing round the inferior oblique muscle and piercing the complexus ; the external branch is seen to the outside ; 2', cranial distribution of the great occipital ; 3, external branch of the posterior primary division of the third nerve ; 3', its internal branch, or third occipital nerve ; 4', 5', 6', 7', 8', cutaneous offsets from the internal branches of the cervical nerves on the left side ; the external branches of these nerves proceeding to muscles are displayed on the right side ; d 1 to d 6, and thence 280 THE SPINAL NERVES. to d 12, external muscular branches of the posterior primary divisions of the twelve dorsal nerves on the right side ; d 1', to d 6', the internal cutaneous branches of the six upper dorsal nerves on the left side ; d 7' to d-12', cutaneous branches of the six lower dorsal nerves from the external branches; I, I, external branches of the posterior primary divisions of several lumbar nerves on the right side piercing the muscles, the lower descending over the gluteal region ; I', I', the same more superficially on the left side (the cutaneous branches of the lower dorsal and upper lumbar nerves are represented as piercing the latissimus too high) : s, s, on the right side, the issue and union by loops of the posterior primary divisions of four sacral nerves ; s', s', on the left side, cutaneous filaments from the internal branches of the lower lumbar and upper sacral nerves. CERVICAL NERVES (excepting the siiboccipital}. — The external branches give only muscular offsets?, and are distributed to the splenius and the slender muscles prolonged to the neck from the erector spinse, viz., the cervicalis ascendens, and the transversalis cervicis with the trachelo-mastoid. That of the second nerve is the largest of the series of external branches of the cervical nerves, and is often united to the corresponding branch of the third. The internal branches, larger than the external, are differently disposed at the upper and the lower parts of the neck. That of the second cervical nerve is named, from its size and destination, the great occipital, and requires separate notice. The rest are directed inwards to the spinous processes of the vertebrae. Those derived from the third, fourth, and fifth nerves pass over the semispinalis and beneath the complexus, giving offsets to those muscles and to the multifidus, and, having reached the spines of the vertebrse, pierce the splenius and trapezius, to be dis- tributed in the integument over the latter muscle. From the cutaneous branch of the third nerve an offset passes upwards to the integument on the lower part of the occiput, lying at the inner side of the great occipital nerve ; this is sometimes called the third occipital nerve. Between the inner branches of the first three or four cervical nerves, beneath the corn- plexus, there are frequently communicating loops ; this communication has been designated by Cruveilhier the posterior cervical plexus. The internal branches from the lowest three cervical nerves are placed beneath the semispinalis muscle, and end in the muscular structure, without furnishing any offset to the skin. These three nerves are the smallest of the series. The great occipital nerve is directed upwards across the inferior oblique muscle, and is transmitted to the surface through the complexus and trapezius muscles, giving twigs to the complexus. Ascending with the occipital artery, it divides into branches which radiate over the back of the head, the most external communicating with the small occipital nerve. Varieties. — The great occipital nerve occasionally sends a branch to the auricle, or replaces, to a greater or less extent, the small occipital nerve (p. 286). The external division of the second nerve is said to give off a cutaneous branch sometimes, or a twig to the superior oblique. Either the sixth or the eighth cervical nerve may furnish a cutaneous branch. On the other hand, the cutaneous branch of the fifth is sometimes wanting. DORSAL NERVES. — The external branches increase in size from above down- wards. They are directed through or beneath the longissimus dorsi to the space between that muscle and the ilio-costalis or accessorius, and supply the several divisions of the erector spinae. The lower five or six nerves give cutaneous twigs, which are transmitted to the integument in a line with the angles of the ribs. The internal branches of the upper six or seven dorsal nerves pass backwards in the interval between the multifidus spinse and the semispinalis muscle ; they supply the transverso-spinales muscles, and become cutaneous by the side of the spinous processes of the vertebras. The cutaneous branch of the second nerve, and sometimes others, extend outwards over the scapula. The internal branches of the POSTERIOR PRIMARY DIVISIONS. 281 lower dorsal nerves are placed between the multifidus spinae and longissimus dorsi, and end in the multifidus without giving branches to the integument. Where cutaneous nerves are supplied by the internal branches, there are generally none from the external branches of the same nerves, and vice versa. The cutaneous offsets of the dorsal nerves run obliquely downwards in their passage between and through the muscles, so that they become superficial and are distributed to the skin at a level below that of the vertebra to which they correspond (see fig-. 189). This descent is but slight in the case of the upper branches, which are derived from the internal divisions of the nerves, and which in their subcutaneous course are directed nearly horizontally outwards, but it becomes progressively greater in the lower branches, proceeding- from the outer divisions, and the offset of the twelfth dorsal only makes its appearance a little distance above the iliac crest. There is considerable variety in the size and in the extent of distribution of the several nerves, which often differ on the two sides of the body ; and twigs from one or two of the lowest dorsal nerves frequently pass over the iliac crest to the skin of the buttock. (See Wardrop Griffith and Oliver, "On the Distribution of the Cutaneous Nerves of the Trunk," Proc. Anatom. Soc., 1890, in Journ. Anat., xxiv.) Varieties. — The cutaneous offset of the first dorsal nerve is sometimes absent. There are not unfrequently cutaneous branches from both divisions of the middle (sixth, seventh, and eighth) dorsal nerves. LUMBAR NERVES. — The external branches enter the erector spinae, and give branches to that muscle. From the upper three, cutaneous nerves are supplied ; and from the last, a filament descends to the corresponding branch of the first sacral nerve. The cutaneous nerves given from the external branches of the first three lumbar nerves (nn. clunium superiores) pierce the fleshy part of the ilio- costalis and the aponeurosis of the latissimus dorsi : they cross the iliac crest near the edge of the erector spinse, and terminate in the integument of the gluteal region. One or more of the filaments may be traced as far as the great trochanter of the femur. The internal branches wind backwards in grooves close below the mamillary processes of the vertebrae, and sink into the multifidus spinse muscle. SACRAL NERVES. — The posterior divisions of these nerves, except the last, issue from the sacrum, through its posterior foramina. The first three are' covered at their exit from the bone by the multifidus spinae muscle, and bifurcate like the posterior trunks of the other spinal nerves ; but the remaining two, which continue below that muscle, are not thus divided. The internal branches of the first three sacral nerves are small, and are lost in the multifidus spinae muscle. The external branches of the same nerves are united with one another, and with the last lumbar and fourth sacral nerves, so as to form a series of anastomotic loops on the upper part of the sacrum. From these, branches are then directed outwards to the cutaneous or posterior surface of the great sacro-sciatic ligament, where, covered by the gluteus maximus muscle, they form a second series of loops, and end as cutaneous nerves (nn. clunium medii). The latter pierce the great gluteus muscle in a line drawn from the posterior superior iliac spine to the tip of the coccyx. They are commonly two in number — one is near the lower part of the sacrum, the other by the side of the coccyx. All are directed outwards over the great gluteal muscle. In six dissections by Ellis the above arrangement was found to be the most frequent. The variations to which it is liable are these : — the first nerve may not take part in the formation of the second series of loops, and the fourth may be associated with them. From the first three sacral nerves filaments are given to the sacro-iliac articulation (Luschka, Rudinger). Small cutaneous twigs from the internal branches of the lower lumbar and upper sacral nerves are described by many anatomists (fig. 188, .s-V). The posterior divisions of the last two sacral nerves are smaller than those above them, and are not divided into external and internal branches. They are connected 282 THE SPINAL NERVES Fig. 189. ANTERIOR PRIMARY DIVISIONS OF CERVICAL NERVES. 283 with each other by a loop on the back of the sacrum, and the lowest is joined in a similar manner with the coccygeal nerve ; one or two filaments from these sacral nerves are distributed in the neighbourhood of the coccyx. COCCYGEAL NERVE. — The posterior division of the coccygeal nerve is very small, and separates from the anterior primary portion of the nerve in the sacral canal. It is joined by a communicating filament from the last sacral nerve, and ends in the integument over the posterior surface of the coccyx. ANTERIOR PRIMARY DIVISIONS OF THE SPINAL NERVES. The anterior primary divisions of the spinal nerves are distributed to the parts of the body situated in front of the vertebral column, including the limbs. They are, for the most part, considerably larger than the posterior divisions, and each is connected by one or two slender filaments with the sympathetic. Those of the cervical, lumbar, and sacral nerves form plexuses of various forms ; but those of the dorsal nerves remain for the most part separate from one another. CERVICAL NEKVES. The anterior divisions of the upper four cervical nerves form the cervical plexus. The first emerges between the rectus lateralis and rectus anticus minor muscles ; and the others, having passed behind the vertebral artery and between the two intertransverse muscles, appear at the side of the neck between the scalenus medius and rectus anticus major muscles. They are each united by a communicating filament Fig. 189.— CUTANEOUS DISTRIBUTION OF THE POSTERIOR PRIMARY BRANCHES OF THE SPINAL NERVES. (GK D. T.) On the right side the nerves are shown lying on the superficial muscles ; on the left side the limit of the skin-area supplied by these nerves is indicated by the dotted line. 7 c, seventh cervical spine ; 6 c?, sixth dorsal ; 12 d, twelfth dorsal ; 5 I, fifth lumbar. The nerves are indicated as follows : — C II, great occipital, from second cervical ; III to V, third to fifth cervical ; D I, first dorsal ; II to XII, second to twelfth dorsal ; three cutaneous branches are given by the sixth dorsal, two from the internal, and one from the external division ; L, lumbar ; S, upper sacral ; C, lower sacral and coccygeal ; A S C, anterior divisions of the last sacral and coccygeal ; P C, perforating cutaneous ; S S, small sciatic to the first cervical ganglion of the sympathetic nerve, or to the cord connecting that ganglion with the second. The anterior divisions of the lower four cervical nerves, larger than the upper four, appear between the anterior and middle scaleni muscles, and, together with the larger part of the first dorsal, go to form the brachial plexus. They are each connected by a filament with one of the two lower cervical ganglia of the sympathetic, and with the plexus on the vertebral artery. The anterior divisions of the first and second nerves require a notice separately from the description of the nerves of the cervical plexus. SUBOCCIPITAL NERVE. The anterior primary division of the first nerve runs forwards in a groove on the outer side of the upper articular process of the atlas, and bends downwards in front of the transverse process of that vertebra to join the second nerve. In this course forwards it lies beneath the vertebral artery, and on the inner side of the rectus lateralis muscle, to which it gives a branch. As it crosses the inner side of the foramen in the transverse process of the atlas, the nerve is joined by a filament from the sympathetic on the vertebral artery. From the loop which it makes in front of the transverse process, twigs are supplied to the two anterior recti muscles, and one or two larger branches pass to the hypoglossal trunk, in connection with which most of the fibres pass down into the descending cervical nerve (p. 273). 284 THE SPINAL NERVES. The loop is also united by short filaments to the superior cervical ganglion of the sympathetic and to the trunk-ganglion of the vagus. Filaments of this nerve are distributed to the articulation of the occipital bone with the atlas, and, according to Valentin, also to the mastoid process of the temporal bone. SECOND CERVICAL NERVE The anterior division of the second cervical nerve, beginning between the arches of the first two vertebrae, is directed forwards between their transverse processes, R.A.M*. l(/9 SUPRACUAVICUUAR Fig. 190. — PLAN OF THE CERVICAL PLEXUS AND ITS CONNECTIONS. (Gr. D. T.) I to V, anterior divisions of the first to fifth cervical nerves ; Sy, communicating branches to the upper cervical ganglion of the sympathetic ; branches to muscles are indicated as follows : — R. L. , rectus lateralis ; R.A.Mi., rectus anticus minor ; R.A.Ma., rectus anticus major ; L.C., longus colli ; St.M., sterno-mastoid ; Sc.A., scalenus anticus ; Sc.M., scalenus medius ; L.S., leva tor scapulae. passing round the outer side of the vertebral artery, and beneath the posterior intertransverse and other muscles fixed to those processes. In front of the THE CERVICAL PLEXUS. 285 intertransverse muscles, the nerve divides into an ascending part, which joins the first cervical nerve, and a descending part to the third. CERVICAL PLEXUS. The cervical plexus is formed by the anterior divisions of the upper four cervical nerves, and distributes branches to some of the muscles of the neck, and 4to a Fig. 191.— THK SUPERFICIAL BRANCHES OF THE CERVICAL PLEXUS. andLeveille.) J (From Sappey, after Hirschfeld 1, superficial cervical nerve (represented too large) ; 2, its inferior branch ; 3, its superior branoh ; 4, its union with the facial ; 5, great auricular nerve ; 6, one of its facial branches ; 7, its branch to the lobule ; 8, twig which pierces the auricle to pass to its outer surface ; 9, branch to the deep surface of the pinna; 10, its union with the posterior auricular of the facial nerve ; 11, small occipital nerve ; 12, its branch which unites with the great occipital nerve ; 13, a mastoid branch arising separately from the plexus ; 14, twigs from this to the back of the neck ; 15, inner, 16, 17. middle, 18, outer branches of the supraclavicular nerves ; 19, branch of the cervical nerves passing into the trapezius muscle ; 20, spinal accessory distributed to the same and receiving a uniting branch from the cervical nerves ; 21, branch to the levator scapulae ; 22, trunk of the facial nerve ; 23, its posterior auricular branch passing into the occipital and postei'ior and superior auricular muscles ; 24, its cervical branch ; 25, great occipital nerve. portion of the integument of the head, neck, and chest. It is placed opposite the first four vertebrae, beneath the sterno-mastoid muscle, and rests against the middle scalenus muscle and the levator anguli scapulae. The disposition VOL. III. PT. 2. T 286 THE SPINAL NERVES. of the nerves in the plexus is as follows : — Each nerve, except the first, divides into an ascending and a descending part ; and these are united in communicating loops with the contiguous nerves. From the union of the second and third nerves, superficial branches are supplied to the head and neck ; and from the junction of the third with the fourth, arise some of the cutaneous nerves of the shoulder and chest. Muscular and communicating branches spring from the same nerves. The BRANCHES of the plexus may be divided into two sets — a superficial and deep ; the superficial consisting of those which perforate the cervical fascia and supply the integument ; the deep comprising branches which are distributed for the most part to the muscles. The superficial nerves may be subdivided into ascending and descending ; the deep nerves into an internal and an external series. SUPERFICIAL ASCENDING BRANCHES. Small occipital nerve. — The small occipital nerve varies in size, and is occasionally double. It springs from the second and third (sometimes only the second) cervical nerves, and is directed almost vertically to the head along the posterior border of the sterno-mastoid muscle, giving off in its course twigs to the skin over the upper portion of the posterior triangular space. Having perforated the deep fascia near the cranium, the small occipital nerve ascends to the scalp between the ear and the great occipital nerve, and ends in cutaneous filaments which extend upwards to somewhat above the level of the ear. It communicates with branches from the great occipital, great auricular and posterior auricular nerves, and it supplies an auricular branch which is distributed to the upper part of the ear on its inner aspect. Varieties. — The small occipital nerve is sometimes directed backwards across the posterior triangle of the neck, and perforates the trapezius muscle close to its upper border, before ascending1 to the head. The auricular branch is occasionally derived from the great occipital nerve. The small occipital is sometimes much reduced in size and distributed solely to the skin of the neck, its place on the head being- taken by branches of the great occipital nerve. Great auricular nerve. — Arising from the second and third cervical nerves, this, the largest of the ascending branches of the plexus, winds round the hinder border of the sterno-mastoid, and is directed obliquely upwards between the platysma myoides muscle and the deep fascia of the neck towards the lobule of the ear. A little below the latter the nerve gives a few small offsets to the face, and then ends in auricular and mastoid branches. (a) The auricular branches are directed to the back of the auricle, on which they ramify, and are connected with twigs derived from the posterior auricular branch of the facial nerve. One offset reaches the outer surface of the ear by a fissure between the antihelix and the concha. A few filaments are supplied likewise to the outer part of the lobule. (#) The mastoid branch ramifies in the integument over the upper end of the sterno-mastoid muscle and the mastoid process, and communicates with the posterior auricular and small occipital nerves. (c) The facial branches are distributed to the integument of the face over the parotid gland. Some slender filaments penetrate into the substance of the gland, and communicate with the lower division of the facial nerve. Varieties. — The great auricular nerve may arise solely from the third, or from the third and fourth cervical nerves (Henle). The mastoid branch is often a separate offset of the plexus, ascending between the great auricular and small occipital nerves (fig. 191, 13). Superficial cervical nerve (n. subcutaneus colli). — This nerve takes origin, usually in common with the great auricular, from the second and third cervical THE CERVICAL PLEXUS. 287 nerves, turns forwards over the sterno-mastoid muscle about the middle, and after perforating the cervical fascia, divides beneath the platysma myoides into two branches, which are distributed to the anterior part of the neck. (a) The upper branch is the larger, and gives an ascending twig which accom- panies the external jugular vein, and communicates freely with the cervical branch of the facial nerve ; it is then transmitted through the platysma to the surface, and ramifies in the integument of the upper half of the front of the neck, filaments reaching as high as the lower maxilla. (b) The lower branch, sometimes represented by two or three smaller offsets, likewise pierces the platysma and is distributed below the preceding, its filaments extending in front as low as the sternum. Varieties. — The superficial cervical nerve also may arise from the third only, or from the third and fourth cervical nerves. It is sometimes represented by two or more branches arising separately from the plexus. SUPERFICIAL DESCENDING BRANCHES. Supraclavicular nerves. — The descending series of the superficial nerves are thus named. They arise together from the third and fourth cervical nerves, and descend in the interval between the sterno-mastoid and the trapezius muscles. As they approach the clavicle, they are three or more in number, and are recognized as internal, middle, and external. (a) The internal branch (suprasternal), which is much smaller than the rest, ramifies over and below the inner third of the clavicle, and terminates near the sternum. From it one or two filaments are furnished to the sterno-clavicular articulation (Riidinger, Hepburn). (b) The middle branch, generally divided into two or three parts, and crossing the clavicle in the interval between the sterno-nlastoidand trapezius muscles, distributes some twigs over the fore part of the deltoid, and others over the pectoral muscle as low as the third rib. The latter join the small anterior cutaneous branches of some of the upper intercostal nerves. (c) The external or posterior branch (supra-acromial) is directed outwards across the clavicular attachment of the trapezius muscle, and ramifies over the acromion and in the integument of the outer and back part of the shoulder. Filaments from these nerves supply the skin over the lower part of the posterior triangular space, and one or two twigs pass backwards over the trapezius to the integument above the spine of the scapula. Variety. — One of the middle branches of the supraclavicular nerves occasionally perforates the clavicle on its way downwards. DEEP BRANCHES : INTERNAL SERIES. Connecting branches. — The cervical plexus is connected near the base of the skull with the pneumo-gastric, hypoglossal, and sympathetic nerves, by means of filaments intervening between those nerves and the loop formed by the first two cervical nerves in front of the atlas (p. 283). Muscular branches. — Branches to the pre vertebral muscles proceed from the cervical nerves close to the vertebrae, including the loop between the first two of these nerves ; and from the fourth nerve a twig is frequently given to the upper part of the scalenus anticus. Two communicating cervical branches, one from the second, the other from the third cervical nerve, descend over or under the internal jugular vein to join the descending cervical nerve in the ansa cervicalis, from which the infrahyoid muscles are supplied (p. 273). T 2 THE SPINAL NERVES. Variety. — In some cases there is also a communicating- branch from the fourth nerve (fig. 183). Phrenic nerve. — The diaphragmatic or phrenic nerve (fig. 183, 9 ; 193, 3) passes down through the lower part of the neck and the thorax to its destination. It arises mainly from the fourth cervical nerve, but it also receives, in the majority of instances, an additional root from either the third or the fifth nerve. While descending in the neck, the nerve inclines inwards over the anterior scalenus muscle ; and near the chest it is joined by a filament from the middle or lower cervical ganglion of the sympathetic. At the root of the neck each phrenic nerve is placed between the subclavian artery and vein, and crosses over the internal mammary artery from without inwards and backwards. It then takes a nearly vertical course, in front of the root of the lung on each side, and along the side of the pericardium — between this and the mediastinal part of the pleura. Near the diaphragm it divides into branches, which pass separately through the muscle, and then diverging from each other, are distributed on the under surface. The right nerve has a more direct course than the left, and lies at first along the outer side of the right innominate vein and the superior vena cava. The left nerve is somewhat longer than the right, in consequence of the oblique position of the heart and pericardium round which it winds, and also because the diaphragm is lower on this than on the opposite side. It passes into the thorax between the left innominate vein and subclavian artery, and then crosses in front of the left vagus and over the left side of the arch of the aorta before reaching the pericardium. Besides the terminal branches supplied to the diaphragm, each phrenic nerve gives on its way through the thora.x filaments to the pleura and pericardium. Luschka describes also twigs from the lower part of the nerve to the peritoneum, and on the right side to the inferior cava and the right auricle of the heart. One or two filaments of the nerve of the right side join in a small ganglion with branches to the diaphragm which are derived from the solar plexus of the sympathetic ; and from the ganglion twigs are given to the suprarenal capsule, the hepatic plexus, and the lower vena cava. On the left side there is a junction between the phrenic and the sympathetic nerves near the oesophageal and aortic openings in the diaphragm, but without the appearance of a ganglion. According to the observations of Pansini in animals (Arch. ital. de Biologic, x, 1888) the terminal ramifications of the phrenic nerves form in the diaphragm a complicated plexus, in which the three last intercostal nerves also take part, and which contains microscopic ganglia. On sensory fibres in the phrenic nerve, see J. Ferguson, in " Brain," 1891. Varieties. — The phrenic may receive an accessory root from the second or the sixth cervical nerve (rarely), from the descend ens cervicis or the ansa cervicalis, or from the nerve to the subclavius (frequently). The last may be of considerable size ; and in some instances the whole nerve has been found arising in this way and descending in front of the third part of the subclavian artery and the subclavian vein to the thorax. The accettory phrenic nerve is a filament arising from the fifth, or more rarely the fifth and sixth cervical nerves, and passing either in front of or behind the subclavian vein to join the trunk at the root of the neck or at a variable level in the thorax. The phrenic nerve, having a normal origin, has been observed in different cases lying along the outer border of, or piercing, the scalenus anticus, crossing in front of the subclavian vein, and passing through a ring formed by that vessel. It occasionally gives a branch to the scalenus anticus. DEEP BRANCHES : EXTERNAL SERIES. Muscular branches. — The sterno-mastoid receives a branch from the second cervical nerve. Two branches proceed from the third and fourth nerves to the levator anguli scapulae ; and from the same nerves, as they leave the spinal canal, THE CERVICAL AND BRACHIAL PLEXUSES. 289 branches are given to the middle scalenus muscle. Farther, the trapezius receives one or more considerable branches which arise from the third and fourth cervical trunks in common with the supraclavicular nerves. Communications with the spinal accessory nerve. — In the substance of the sterno-mastoid muscle, this nerve is connected with the branch of the cervical plexus furnished to that muscle. It is also connected with the branches distributed to the trapezius — the union between the nerves being beneath the muscle, and having the appearance of a plexus ; and with another branch of the cervical plexus in the interval between the two muscles. SUMMARY OF THE CERVICAL PLEXUS. — From the cervical plexus cutaneous nerves are distributed to the side of the head, to part of the ear and face, to the anterior two-thirds or more of the neck, and to the upper part of the chest and shoulder. The muscles supplied with nerves from the plexus are the sterno-mastoid, the trapezius, and the int'rahyoid muscles, the anterior and lateral recti capitis, the longuscolli, the levator anguli scapulae, the scalenus medius and anticus in part, and the diaphragm. By means of its branches the plexus communicates with the pneumo-gastric, spinal accessory, hypoglossal, and sympathetic nerves. BRACHIAL PLEXUS. This large plexus, from which the nerves of the upper limb are supplied-, is formed by the union of the anterior trunks of the four lower cervical and the greater part of the first dorsal nerves. It also receives in many cases a fasciculus from the lowest of the nerves (fourth) which go to form the cervical plexus, or a filament from the second dorsal nerve : these two roots may co-exist. The plexus extends from the lower part of the neck to the axillary space, and terminates opposite the coracoid process of the scapula in large nerves for the supply of the limb. The cervical or supraclavicular portion of the plexus, emerging from the cleft between the scalenus anticus and medius, lies in the lower part of the posterior triangular space, above and behind the third part of the subclavian artery : it is crossed by the posterior belly of the omo-hyoid muscle, and is often pierced by the transverse cervical or posterior scapular artery. After passing behind the clavicle, the axillary or infraclavicular portion of the plexus is placed to the acromial side of the axillary vessels, being enclosed in the axillary sheath, and covered by the pectoralis major and subclavius muscles ; and at its termination it lies between the pectoralis minor and subscapularis muscles. The manner in which the nerves are disposed in the plexus is liable to some variation, but the following may be regarded as the typical arrangement, from which the different forms met with may in most cases be readily derived. The fifth and sixth cervical join together at the outer border of the scalenus medius to form an upper trunk ; similarly the eighth cervical and first dorsal unite together between the scaleni muscles to form a lower trunk ; while the seventh cervical remains single, forming a middle trunk. Soon after passing the outer border of the scaleni muscles, each primary trunk divides into an anterior and a posterior branch. The posterior branch of the lower trunk, however, is much smaller than the others, and in most instances is derived solely from the eighth cervical nerve. The anterior branches of the upper and middle trunks unite together to form what is called the upper or outer cord of the plexus ; the large anterior branch of the lower trunk forms by itself the lower or inner cord of the plexus ; and the posterior branches of all three trunks unite together to form the middle or posterior cord. The cords thus formed lie at first in a single bundle on the outer side of the first part of the axillary artery, but lower 290 THE SPINAL NERVES. down they are placed, the first on the outer side, the second on the inner side, and the third behind that vessel in its second part, whence they are continued into the principal nerves for the arm. Varieties. — Deviations from the arrangement above described, depending* upon alterations in the level at which the several portions of the plexus separate and unite, are often met with. The seventh cervical nerve is sometimes divided into three branches, one passing- to each of the three cords of the plexus. The posterior cord has been observed arising* from the sixth, seventh, and eighth, and in one case only from the seventh and eighth cervical nerves (Turner). Cases are recorded in which the plexus consisted of only two cords, the larger one representing- either the inner and outer, or the posterior and inner cords of the normal arrangement. The fifth cervical nerve is not unfrequently, the sixth more rarely, directed outwards through the fibres of the scalenus anticus ; the fifth nerve may even pass altogether in front of that muscle. BRANCHES. — The nerves proceeding from the brachial plexus are usually divided into two classes, viz., A, those that are given off from its supraclavicular part, and w musculo-spiral ; humeral nerve. circumflex ; i,i, intercostal nerves ; Fig. 192. — PLAN OF THE CERVICAL AND BRACHIAL PLEXUSES. (Allen Thom- son). i The nerves are separated from the spinal cord at their origin and are sup- posed to be viewed from before : CI, the first cervical or suboccipital nerve, and the Roman numbers in succession from II, to VIII, the corresponding cervical nerves ; DI, the first, and II, and III, the second and third dorsal nerves ; the origin of the posterior piimary branch is shown in all the nerves ; of these p 2, indicates the great occipital from the second, and p 3, the smallest occipital nerve from the third. Cervical plexus : 1, anterior primary branch of the first cervical nerve and loop of union with the second nerve ; 2, small occipital nerve ; 3, great auricular nerve ; 3', superficial cervical nerve : 3 n, communicating branches to the ansa cervicalis from the second and third ; 3 s, communicating to the spinal accessory from the third and fourth nerves ; 4, supraclavicular nerves ; 4', phrenic nerve. Brachial plexus : V, to VIII', and D', the five roots of the brachial plexi>s ; 5, tbe rhomboid nerve ; 5', suprascapular ; 5", posterior thoracic ; 6, nerve to the subclavius muscle ; 7, 7, inner and outer anterior thoracic nerves ; 8, 8', 8", subscapular nerves. In the larger nerves proceeding to the shoulder and arm from the plexus, those of the anterior divisions are represented of a lighter shade, those belonging to the posterior division darker ; ec, external cutaneous or musculo-cutaneous ; m, median ; n, ulnar ; ic, internal cu- taneous ; w, nerve of Wrisberg ; r, lateral branch of the same ; ih, intercosto- so arise before the formation of the three cords of the plexus ; and B, those arising below the clavicle from the outer, inner, and posterior cords. To the former (supraclavicular) group belong some small muscular nerves to the scaleni and longus colli muscles the nerve to the rhomboid muscles, the posterior THE BRACHIAL PLEXUS. 291 thoracic nerve for the serratus magnus muscle, the suprascapular nerve, the nerve to the subclavius, and sometimes a branch to join the phrenic nerve. The nerves given off below the clavicle are derived from the three great cords of the plexus in the following manner : — From the upper or outer cord,— the external of the two anterior thoracic nerves, the nerve to the coraco-brachialis, the musculo-cutaneous, aud the outer head of the median. From the lower or inner cord,— the inner of the two anterior thoracic nerves, the nerve of Wrisberg or small internal cutaneous, the internal cutaneous, the ulnar, and the inner head of the median. From the posterior cord, — the three subscapular nerves, the circumflex, and the musculo-spiral. The following table shows the spinal nerves from which the several offsets of the plexus are commonly derived.1 + signifies that the branch in question receives fibres from the spinal nerve in whose column the sign is placed ; + ? signifies that there is most frequently a root from that spinal nerve, but it may be wanting ; ? signifies that the corresponding root is not unfrequently present, although exceptional. The rarer forms of variation are not taken into account : — C. V. C. VI. C. VII. C. VIII. D. 1. A. SUPRACLAVICULAR BRANCHES. a. To trunk-muscles. To longus colli ..... + ? + ? + ? + ? To scaleni ...... + + ? To phrenic nerve .... ? b. To limb- muscles. To rhomboidei . ... -f Posterior thoracic .... + + + ? Suprascapular ... . . + + ? To subclavius ..... + 1 B. INPRACLAVICULAR BRANCHES. a. From outer cord. ~_ External anterior thoracic . . . + ? + + To coraco-brachialis .... + Musculo-cutaneous . . . + + Outer head of median + + 6. From inner cord. Internal anterior thoracic . . . -f- _|- Nerve of Wrisberg .... + Internal cutaneous . . . . + + Ulnar ...... •t _j_ _i_ Inner head of median . . . . f + + c. From posterior cord. « Upper subscapular .... + + Middle or long subscapular . ? + ? Lower subscapular .... + ? + ? Circumflex . . . ... + + 1 Musculo-spiral .... ? + + + A. — BRANCHES ABOVE THE CLAVICLE. Small muscular branches. — The branches for the scaleni and longus colli muscles spring in an irregular manner from the lower cervical nerves close to their place of emergence from the intervertebral foramina. Branch to the phrenic nerve. — This small branch is, when present, an offset from the fifth cervical nerve ; it usually joins the phrenic nerve on the anterior scalenus muscle. 1 See W. P. Herringham, 1886. The Minute Anatomy of the Brachial Plexus," Proc. Roy. Soc., xli, 292 THE SPINAL NERVES. Varieties. — The communicating branch to the phrenic nerve has been seen to pass down into the thorax over the subclavian artery, and even over the vein, before joining- with the trunk. A second filament to the, phrenic, from the sixth nerve, is rarely met with. The branch for the rhomboid muscles (n. dorsal-is scapula) arises in common with the highest root of the posterior thoracic nerve from the fifth nerve Fig. 193. — DEEP DISSECTION OF THE AXILLA, SHOWING THE BRACHIAL PLEXUS AND NEIGHBOURING NERVES. (From Sappey, after Hirscbfeld and Leveille.) £. The clavicle has been sawn through near its sternal end, and is turned aside with the muscles attached to it ; the subclavius and the greater and lesser pectoral muscles have been removed from the front of the axilla. 1, ansa cervicalis ; 2, pneumo-gastric ; 3, phrenic, passing down to the inner side of the scalenus anticus muscle ; 4, anterior primary division of the fifth cervical nerve ; 5, 6, 7, the same of the sixth, seventh, and eighth cervical nerves ; 8, the same of the first dorsal 'nerve ; 9, 9, nerve to the subclavius muscle, communicating with the phrenic nerve ; 10, posterior thoracic nerve distributed to the serratus magnus ; 11, external anterior thoracic nerve, passing into the great pectoral muscle; 13, internal anterior thoracic, distributed to the lesser pectoral ; 14, twig of communication between these two nerves ; 12, suprascapular nerve, passing through the suprascapular notch ; 15, upper subscapular nerve ; 16, lower subscapular nerve ; 17, long subscapular nerve ; 18, 21, small internal cutaneous nerve ; 19, union of this with the second and third intercostal nerves ; 20, lateral branch of the second intercostal ; 22, internal cutaneous nerve ; 23, ulnar nerve to the inside of the axillary artery, passing behind the vein, and having, in this case, a root from the outer cord of the plexus ; 24, median nerve immediately below the place where its two roots embrace the artery, which is divided above this place ; 25, musculo-cutaneous nerve, passing into the coraco-brachialis muscle, to which it is giving a branch ; 26, musculo-spiral nerve, passing behind the divided axillary artery. close to the vertebrae, and is directed backwards to the base of the scapula through the fibres of the middle scalenus, and beneath the levator anguli scapulae, to the deep surface of the rhomboid muscles, in which it terminates. It gives one or two branches to the levator scapulae, and sometimes a twig to the highest digitation of the serratus posticus superior (Rielander). THK BKACHIAL PLEXUS. 293 The posterior thoracic nerve (n. thoracalis longus] usually arises by three roots from the fifth, sixth, and seventh cervical nerves. The upper and middle roots perforate the scalenus rnedius and join either in the substance or on the surface of that muscle : the lower root passes in front of the scalenus medius and joins the trunk opposite or below the first rib. The nerve descends behind the brachial plexus and the first part of the axillary artery, on the outer surface of the serratus inagnus, nearly to the lower border of that muscle, supplying it with numerous branches. The fibres derived from the several roots are distributed to the slips of the muscle in order from above downwards. Varieties. — The root from the seventh nerve is sometimes wanting1. In three instances the nerve was found by Lucas receiving a fourth root from the eighth cervical nerve. The root from the fifth nerve sometimes remains separate, being- distributed only to the upper division of the muscle. The suprascapular nerve arises from the trunk formed by the union of the fifth and sixth cervical nerves, but its fibres are derived mainly from the fifth nerve. It passes outwards and backwards beneath the trapezius and omo-hyoid muscles to Fig. 194. — DISTRIBUTION OP THE SUPRA- SCAPULAR AND CIRCUMFLEX NERVES. (Hirschfeld and Leveille. ) ^ a, scalenus medixis and posticus muscles ; b, levator anguli scapulae ; c, acroraion ; d, deltoid muscle, of which the back part has been removed ; e, rhomboid muscles ; /, teres major ; g, latissimus dorsi ; 1, the bra hial plexus, seen from behind ; ]', nerve to the rhomboid muscles ; 2, placed on the clavicle, the suprascapular nerve ; 3, its branches to the supraspinatus muscle ; 4, branch to the infraspinatus ; 5, the circum- flex nerve, passing out of the quadrangular interval ; 6, its branch to the teres minor muscle; 7, branches to the deltoid; 8, cutaneous branch. the uppf r border of the scapula, where it enters the supraspinous fossa through the suprascapular notch, below the ligament of the same name. In the supraspinous fossa, the nerve supplies branches to the supraspinatus muscle, and a slender articular filament to the shoulder-joint ; and it then descends through the great scapular notch to the lower fossa, where it ends in the infraspinatus muscle, furnishing sometimes a second twig to the articulation of the shoulder. Varieties. — The suprascapular nerve is sometimes derived eolely from the fifth nerve ; or it may receive a few fibres from the fourth nerve. It has been seen dividing1 into two parts, the one of which passes through the suprascapular notch, while the other pierces the bone just below the notch. Very rarely a branch is given to the upper part of the subscapularis muscle, or to the teres miuor. Filaments to the acromio-clavicular articulation have been noticed by Riidinger, and to the periosteum and substance of the scapula by Swan and Ellis. The nerve of the subclavius muscle, a slender branch given off from the front of the upper trunk of the plexus, is also derived mainly or wholly from the fifth cervical nerve. It descends over the third part of the subclavian artery and behind the clavicle to the posterior surface of its muscle. Varieties. — The nerve to the subclavius often sends a branch inwards to join the phrenic nerve either at the root of the neck (fig. 193) or, less frequently, in the thorax. A communicating twig to the external anterior thoracic nerve, and a branch to the clavicular head of the sterno-mastoid have also been observed (Turner). 294 THE SPINAL NERVES. B. — BRANCHES BELOW THE CLAVICLE. Anterior thoracic nerves. — The anterior thoracic nerves, two in number, supply the pectoral muscles. The external, or more superficial branch, arising from the outer cord under cover of the clavicle, is derived from the sixth and seventh nerves, very frequently also the fifth. It crosses inwards over the axillary artery, and, after giving off a branch to join the inner nerve, terminates in the great pectoral muscle. The internal, or deeper branch, springing from the inner cord, mostly receives fibres from both the last cervical and first dorsal nerves. It comes forwards between the axillary artery and vein, and is joined by the communicating branch from the external nerve, with which it forms a plexiform loop embracing the axillary artery. From this loop offsets proceed to the small and to the lower part of the large pectoral muscles. Varieties. — The internal branch occasionally has no fibres from the first dorsal nerve. Cutaneous filaments from the anterior thoracic nerves to the mammary region and to the arm have been described by various observers. The external branch is said to supply twigs sometimes to the clavicular part of the deltoid ; and, according to Bock and Valentin, a filament is given to the acromio-clavicular articulation. Subscapular nerves. — The subscapular nerves are usually three in number, and supply the muscles forming the posterior wall of the axilla. The upper nerve, the smallest of the three, is derived from the fifth and sixth cervical nerves, and penetrates the upper part of the subscapularis muscle. This branch is often double. The middle or long subscapular nerve (n. thoraco dor sails) is the largest of the three, and obtains its fibres mainly from the seventh, to a less extent in many cases also from the sixth or eighth cervical nerves. It descends in company with the subscapular artery to enter the deep surface of the latissimus dorsi muscle. The lower subscapular nerve is derived from the fifth and sixth, or less frequently the sixth and seventh cervical nerves. It gives one or two branches to the lower part of the subscapularis, and ends in the teres major muscle. Varieties. — The upper nerve occasionally proceeds from the fifth or sixth cervical nerve alone. The most frequent origin of the long subscapular ncrrc is from the seventh alo.ie, or from the seventh and eighth nerves ; it rarely receives fibres from the fifth. The lower nrrcc seldom proceeds from the fifth or sixth nerve alone, or from the fifth, sixth, and seventh nerves. The branches to the lower part of the subscapularis and the teres major muscles are sometimes independent offsets of the brachial plexus. The nerve to the teres major is occasionally given off by the commencement of the circumflex nerve. Circumflex nerve. — The circumflex nerve (n. axillaris), one of the terminal branches of the posterior cord of the plexus, obtains its fibres from the fifth and sixth cervical nerves. It is placed at first behind the axillary artery, resting on the subscapularis muscle, at the lower border of which it turns backwards with the posterior circumflex vessels. It then appears at the back of the shoulder in the quadrilateral space between the two teres muscles (fig. 194), external to the long head of the triceps, and divides into branches, which are distributed to the deltoid and teres minor muscles, the integument of the shoulder, and the shoulder-joint. (a) The upper branch winds round the upper part of the shaft of the humerus, extending nearly as far as the anterior border of the deltoid muscle, to which it is distributed. One or two cutaneous filaments penetrate between the muscular fibres, and are bent downwards to supply the integument over the lower part of the muscle. (b) The lower branch supplies offsets to the back part of the deltoid, and THE CIRCUMFLEX NERVE. 295 furnishes the nerve to the teres minor, on which there is often a small reddish enlargement. It then turns round the posterior border of the deltoid below the Fig. 195. — DISTRIBUTION OP THE POSTERIOR CUTANEOUS NERVES OF THE SHOULDER AND ARM (Hirsclifelcl and Leveille. ) I 1, supra -acromia) branches of the cervical plexus descending on the deltoid muscle ; 2, ascending and 2', descending cutaneous branches of the circumflex nerve ; 3, inferior external cutaneous of the musculo- spiral nerve ; 4, posterior cutaneous branches of the musculo-cutaneous nerve to the forearm ; 5, 6, internal cutaneous of the musculo- spiral ; 7, nerve of Wrisberg ; 8, 9, posterior branches of the internal cutaneous nerve. middle, and ramifies in the integument over the lower two- thirds of that muscle, and over the adjacent part of the triceps (n. cutaneus Irachii lateralis). (c) One or two articular filaments for the shoulder- joint arise near the commencement of the nerve, and enter the capsular ligament below the subscapular muscle. Rauber describes a filament of the upper branch as ascending in the bicipital groove to be distributed to the upper extremity of the humerus and the capsule of the shoulder- joint. Varieties. — The circumflex nerve is occasionally derived wholly from the fifth cervical ; and the contribution from the sixth nerve is often very small. It has been seen to perforate the lower part of the subscapularis muscle (Macalister, Bubenik), to which it often furnishes a branch. Branches to the long- head of the triceps and to the infraspinatus are also mentioned. Internal cutaneous nerve. — The internal cutaneous nerve (n. cutaneus antibrachii medialis) is composed of fibres proceeding from the first dorsal, and usually also from the eighth cervical nerve. After leaving the inner cord of the plexus, it is placed at first to the inner side of the axillary artery, and then descends superficially between the brachial artery and the basilic vein to rather below the middle of the arm, where it becomes subcutaneous. As it pierces the fascia it is divided into two parts, one destined for the anterior, the other for the posterior surface of the forearm. (a) The anterior division crosses at the bend of the elbow behind (less frequently over) the median-basilic vein, and distributes filaments in front of the forearm, as far as the wrist ; one of these may be joined with a cutaneous branch of the ulnar nerve (fig. 197, 14). (b) The posterior division, smaller than the anterior, inclines to the inner side of the basilic vein, and sends its branches obliquely backwards round the inner margin of the forearm to supply the skin about as far as the subcutaneous border of the ulna. Above the elbow this division is connected with the small internal cutaneous nerve ; in the forearm it communicates with the anterior part of the internal cutaneous, and near the wrist sometimes with the dorsal branch of the ulnar nerve. (c) One or more branches to the integument of tlie arm pierce the fascia near the axilla, and reach to the elbow, or nearly so, distributing filaments outwards over the biceps muscle. Varieties. — The posterior division of the internal cutaneous nerve has been seen arising separately from the posterior branch of the lower trunk of the brachial plexus (G-. Elliot Smith, Journ. Anat.. xxix, 85). Cases are recorded in which the posterior division is joined, 296 THE SPINAL NERVES. or replaced to a greater or less extent, by a branch of the ulnar nerve. In one instance the posterior branch was large and extended to the hand, taking the place of the absent dorsal branch of the iilnar nerve (Gr. D. T.). Fig. 196. — ANTERIOR CUTANEOUS NERVES OF THE SHOULDER AND ARM. (From Sappey, after Hirschf eld and Leveille. ) 1 1, 1, supraclavicular nerves from the cervical plexus ; 2, 2, 2, cutaneous branches of the circumflex nerve ; 3, 4, upper branches of the internal cutaneous nerve ; 5, upper external cutaneous branch of the musculo-spiral ; 6, internal cutaneous nerve piercing the deep fascia ; 7, its posterior branch ; 8, communicating twig with one of the anterior branches ; 9, 10, anterior branches of this nerve, some turning round the median basilic and ulnar veins ; 11, musculo- cutaneous nerve descending (exceptionally) over the median- cephalic vein ; 12, lower external cutaneous branch of the musculo- spiral nerve. Fig. 197. — ANTERIOR CUTANEOUS NERVES OF THE FOREARM AND HAND. (From Sappey, after Hirschf eld and Leveille.) i 9, 10, 13, distribution of the anterior division of the internal cutaneous nerve ; 14, union of one of these with a twig of the ulnar nerve ; 12, lower external cutaneous branch of the musculo-spiral nerve ; 11, 15, distribution of the external cutaneous nerve ; 16, union of one of its branches with 17, the radial nerve ; 18, palmar cutaneous branch of the median nerve ; 19, 20, internal and external digital branches to the thumb from the median nerve; 21, external digital to the index finger; 22, 23, digital branches to the index, middle, and ring fingers ; 24, 25, digital branches from the ulnar nerve to the ring and little fingers. Small internal cutaneous nerve.— The small internal cutaneous nerve or nerve of Wrisberg (n. cutaneus brachn medialis), derived from the first dorsal nerve, commonly arises from the inner cord of the brachial plexus in union with the large internal cutaneous nerve. In the axilla it lies at first behind the axillary vein, but it soon appears on the inner side of that vessel, and communicates with the intercosto-humeral nerve. It then descends along the inner side of the basilic vein THE MUSOULO-CUTANEOUS NERVE. 297 to about the middle of the arm, where it pierces the fascia, and its filaments are thence continued to the interval between the internal condyle of the humerus and the olecranon. Varieties. — The small internal cutaneous may receive fibres from the eighth cervical (rarely) or the second dorsal nerve. The connection iriHi flic fateroosto-kufaeral nerve presents much variety in different cases : — in some, there are two or more intercommunications. ' forming a kind of plexus on the posterior boundary of the axillary space ; in others the intercosto-humeral nerve is of larger size than usual, and takes the place of the nerve of Wrisberg, only receiving in the axilla a small filament from the brachial plexus, and this small communicating filament represents in such cases the nerve of Wrisberg. It sometimes communicates also with the lateral cutaneous branch of the third intercostal nerve. Absence of the nerve of Wrisberg is noted. The nerve to the coraco-brachialis is a small branch formed by fibres derived from the seventh cervical nerve. In the infant it is a separate offset from the outer cord of the plexus, but in the adult it is commonly more or less closely united to the trunk of the mnsculo-cutaneous nerve, from which it separates before that nerve enters the muscle (Herring-ham). It is often represented by two filaments. Musculo cutaneous nerve. — The musculo-cutaneous or external cutaneous nerve, derived from the fifth and sixth cervical nerves, is deeply placed between the muscles as far as the elbow, and below that point is immediately under 'the integument. Arising from the outer cord of the brachial plexus opposite the small pectoral muscle, it perforates the coraco-brachialis, and, passing obliquely across the arm between the biceps and brachialis anticus muscles, reaches the outer side of the biceps a little above the elbow. Here it perforates the fascia, and, passing behind the median-cephalic vein, divides into two branches which supply the integument on the outer side of the forearm, one on the anterior, the other on the posterior aspect. A. Branches in the arm. In addition to the one or two twigs to the coraco-brachialis which may be given off from this nerve near its origin (see above), the musculo-cutaneous furnishes the following offsets in the deep part of its course : — (a) Branches to the biceps and brachialis anticus muscles, which arise after the nerve has pierced the coraco-brachialis. (b) A slender branch to the humerus, entering the bone with the medullary artery. (c) An articular filament to the elbow-joint. The nerve to the humerus is described by Rauber and others as arising from the nerve before it enters the coraco-brachialis, and descending along the brachial artery, to which it supplies filaments ; but Testut states that in all the cases in which he found this branch it was given off by the nerve to the brachialis anticus. An articular filament may proceed from the nerve to the biceps (Cruveilhier) or from that to the brachialis anticus (Riidinger) ; Testut traced a twig from the latter source to the periosteum about the coronoid fossa. A vascular branch to the lower part of the brachial artery from the nerve of tho brachialis anticus is described by Swan and Testut. B. Branches in the forearm. (a) The anterior branch descends near the radial border of the forearm. It is placed in front of the radial artery near the wrist, and distributes its terminal offsets over the thenar eminence. One or two filaments pierce the fascia and run on the artery to the articulations of the wrist. This part of the nerve is connected above the wrist with a branch of the radial nerve. (b) The posterior branch is directed outwards to the back of the forearm, and 298 THE SPINAL NERVES. ramifies in the integument of the lower two-thirds, extending as far as or somewhat beyond the wrist. It communicates with a branch of the radial nerve, and with the lower external cutaneous branch of the musculo-spiral nerve. Varieties. — The musculo-cutaneous nerve proper occasionally receives fibres from the seventh cervical nerve. In some cases the constituent fibres of the nerve remain adherent to the outer head and 10 Fig. 198. — DEEP VIEW OF THE ANTERIOR NERVES OF THE SHOULDER AND ARM. Hirschfeld and Leveille.) | (From Sappey, after 1, musculo-cutaneous nerve, giving off 2, the branch to the coraco-brachialis muscle ; 3, branch to the biceps, represented incorrectly as given off before the nerve pierces the coraco-brachialis ; 4, branch to brachialis anticus ; 5, communicating branch from the median to the musculo-cutaneous nerve (an infrequent variety) ; 6, continuation of the nerve to its cutaneous distribution ; 7, musculo-spiral nerve in the interval between the brachialis anticus and supinator longus muscles ; 8, inferior external cutaneous branch of the musculo-spiral ; 9, the large and small internal cutaneous nerves divided ; 10, anterior branch of the internal cutaneous • 11, median nerve; to the inner side of this the ulnar nerve is crossed by the line from 11. Fig. 199. — DEEP VIEW OF THE ANTERIOR NERVES OF THE FOREARM AND HAND. Hirschfeld and Leveille.) | (From Sappev, after 12, median nerve ; 13, its branch to the pronator teres ; 14, branch to the superficial fle>or muscles, which have been removed ; 15, branch to the flexor profundus digitorum ; 16, branch to the flexor longus pollicis ; 17, anterior interosseous nerve ; 18, palmar cutaneous branch cut short ; 19, branch to short muscles of thumb ; 20, 21, digital branches to thumb ; 22, 23, 24, third, fourth, and fifth digital branches ; 25, branch given by ulnar nerve to flexor carpi ulnaris ; 26, branch to flexor profundus digitorum ; 27, cutaneous twig ; 28, dorsal branch of .ulnar ; 29, superficial palmar portion ; 30, 31, digital branches to ring and little fingers ; 32, deep palmar branch ; 33, its branch to short muscles of little finger ; 34, 35, 36, twigs given by deep branch of ulnar to third and fourth lumbricales, all the interosseous muscles, and the adductors of the thumb. THE MUSCULO-CUTANEOUS NERVE. 299 trunk of the median for a variable distance in the upper part of the arm, the musculo- cutaneous or its several branches then being1 given off from the median tru..k, and pissing outwards to the interval between the biceps and brachialis anticus muscles : this is a common arrangement in lower mammals. In other cases (2 per cent., Testut ; 8 per cent., Villar) only a part of the fibres take this course, so that a communicating branch runs from the median to the musculo-cutaneous (fig. 11)8. 5) ; or the muscular part of the nerve perforates the coraco- brachialis and the cutaneous part is given off from the median (Schwalbe) ; or the median furnishes only the muscular branches (Villar). Much more frequently (36 per cent.. Testut) some of the median fibres are associated with the musculo-cutaneous in its passage through the coraco-brachialis. a communicating branch then passing from the latter nerve to the median. Very rarely the whole outer cord of the plexus pierces the coraco-brachialis, and then divides into musculo-cutaneous and outer head of the median. (Testut, " Recheiches anatomiques sur 1'anastomose du nerf musculo-cutane avec le nerf median," Journ. de 1 Anat., 188:5 ; and " Memoire sur la portion brachiale du nerf musculo-cutaue," Internat. Monatschr. f. Anat., 1884; F. Villar, •' Quelques recherches sur les anastomoses des nerfs du membre superieur." Bull. Soc. Anat. de Paiis. 188S.) Sometimes the musculo-cutaneous nerve does not perforate the coraco-brrchialis, in which case it may pass eirher behind that muscle, or between the coraco-brachialis and the short head of the biceps. The nerve has also been seen perforating the short head of the biceps, or the brachialis anticus, as well as the coraco-brachialis. In rare cases a branch is given to the pronator teres muscle. The terminal porlion of the nerve is not unfrequently continued on the back of the hand to the skin over the first metacarpal bone and the adjoining interosseous space. Hepburn found the musculo-cutaneous supplying the back' of the thumb in a case in which the radial nerve was wanting ; and H. Virchow and Th. Kolliker describe a case in which it gave the dorsal digital nerves to both sides of the ring and the radial side of the little fingers. SUMMARY. — The musculo-cutaneous nerve supplies the biceps and brachialis anticus muscles, the integument on the outer side of the forearm, the humerus, and the elbow and wrist-joints. Communications are established between it and the radial and the lower external cutaneous branch of the musculo-spiral. Ulnar nerve. — The ulnar nerve, the largest branch of the inner cord of the brachial plexus, receives its fibres from the last cervical and first dorsal nerves. From its origin, where it is placed between the axillary artery and vein, it descends on the inner side of the main artery of the limb as far as the middle of the arm, and thence with the inferior profunda artery along the back of the internal inter- muscular septum, being often lodged in a grcove in the substance of the inner head of the triceps muscle, to the interval between the olecranon and the inner condyle of the humerus. In the arm it is covered only by the fascia, and it may be felt through the integument a little above the elbow. It next passes between the two heads of the flexor carpi ulnaris muscle, under cover of which it is continued with a straight course as far as the wrist, resting on the flexor profundus digitorum. The nerve meets the ulnar vessels somewhat above the middle of the forearm, and from this point it remains in contact with them on their inner side. Above the wrist it gives off a large dorsal branch to the hand, and the trunk then runs over the front of the annular ligament, being placed between the ulnar artery and the pisiform bone, to terminate as it enters the palm by dividing into superficial and deep parts. The ulnar nerve usually gives off no branches in the upper arm. A. Branches in the forearm. (a) Articular filaments are given to the elbow-joint as the nerve passes behind it. (b) Muscular branches (Sc,ld) arise from the nerve near the elbow, and pass to the flexor carpi ulnaris and the inner half of the flexor profundus digitorum muscles. (c) Cutaneous branches. — These two small nerves arise about the middle of the forearm by a common trunk. One pierces the fascia, and turning downwards, joins a branch of the internal cutaneous nerve : this branch is often absent. The second, a palmar branch, lies on the ulnar artery, which it accompanies to the hand. This little nerve gives filaments around the vessel, and ramifies in the integument of the 300 THE SPINAL NERVES. inner part of the palm, joining in some cases with other cutaneous offsets of the ulnar or median nerve. (d) Dorsal branch to the hand. — This large offset (8 c). leaving the trunk of the ulnar nerve two or three inches above the wrist, winds backwards beneath the flexor carpi ulnaris, gives a twig over the back of the wrist which usually joins in a loop with an offset of the radial nerve, and then divides into branches : one of these ramifies on the inner side of the little finger ; another divides to supply the contiguous sides of that finger and the ring finger ; a third supplies in part the contiguous sides of the ring and middle fingers, and usually communicates with the branch of the radial passing to the same interspace ; while a fourth is distributed to the skin of the metarcarpal region of the hand, often extending to the base of the index finger (fig. 201 A). The dorsal digital branches on the little finger reach as far as the nail ; on the ring finger they do not usually reach beyond the second phalanx. On the sides of the fingers they form communications with the corresponding volar digital nerves. B. Branches in the palm. (a) The niperfiaalpartot the ulnar nerve (1 d, or 8 c, 1 d) supplies filaments to the palmaris brevis muscle and the integument of the hypothenar eminence, and divides into two digital branches. One of these passes to the ulnar side of the little finger ; the other is connected in the palm of the hand with the innermost digital branch of the median nerve, and at the cleft between the little and ring fingers, divides into the collateral nerves for these fingers. From the communicating branch with the median nerve filaments are sent to the skin and vessels of the palm. The terminal disposition of the digital branches on the fingers is the same as that of the median nerve, to be presently described. (b) The deep part (8 c) sinks backwards with the deep branch of the ulnar artery between the abductor and flexor brevis minimi digiti muscles, and passing to the inner side of and below the hook of the unciform bone (which it sometimes grooves1), through the cleft in the opponens minimi digiti muscle (Vol. II, p. 238), follows the course of the deep palmar arch across the hand. It supplies the short muscles of the little finger as it passes between them ; as it lies over the metacarpal bones it distributes branches to the interosseous muscles and the inner two lumbricales ; and at the outer side of the palm it terminates in offsets to the adductores pollicis and the abductor indicis muscles. Articular filaments pass upwards to the wrist, and others descend to the metacarpo-phalangeal articulations (Riidinger). Rauber also describes small perforating branches, which accompany the superior perforating arteries in the interosseous spaces, and join the terminal filaments of the posterior interosseous nerve. Varieties. — The ulnar nerve not unfrequently has an additional root from the seventh cervical nerve. It is rarely derived wholly from the eighth nerve, or from the seventh and eighth cervical. In a few instances the nerve has been seen descending in front of the inner condyle instead of behind. Cases are also recorded in which the ulnar nerve slipped forwards over the internal condyle when the elbow was bent. A branch may pass from tLe ulnar nerve in the arm to reinforce the internal cutaneous (p. 295). A communication between the ulnar and median nerves in the arm was seen by Villar, and also a communication with the musculo-spiral (Bull. Soc. Anat. Paris, 1888, 613). A branch from the median to join the ulnar in the forearm is of frequent occurrence (p. 302). When the occasional epitrochleo- anconeus muscle (Vol. II, p. 225) is present, it receives a branch from the ulnar nerve. Filaments of the ulnar nerve have been found passing- to the inner part of the triceps, or to the flexor sublimis digitorum, and from the deep part to the second (H. St. John Brooks, Testut), or to the first lumbricalis (J. T. Wilson), or to the outer head of the flexor brevis pollicis (normal according to Swan and Brooks). The dorsal branch may be smaller than 1 W. Anderson, "A Note on the Course and Relations of the Deep Branch of the Ulnar Nerve," Proc. Auat. Soc., Feb. 6, 1894. THE MEDIAN NERVE. 301 usual, or even absent, in £which case the deficiency is generally compensated by the radial nerve (p. 306). in rare cases by the lower external cutaneous of the musculo-spiral (p. 304), or by the internal cutaneous (p. 296). Its area of digital distribution is seldom increased, but it was found by Hepburn supplying1 all four finders in a case of absence of the radial nerve. Its filaments often reach to the radial side of the second metacarpal bone, and in one instance they were followed by Zander to the back of the first phalanx of the thumb. SUMMARY. — The ulnar nerve gives cutaneous filaments to the lower part of the forearm (to a small extent), and to the inner part of the hand on its palmar and dorsal aspects. It supplies the following muscles, viz., the ulnar flexor of the carpus, the deep flexor of the fingers (its inner half), the short muscles of the little finger with the palmaris brevis, the interosseous muscles of the hand, the inner two lumbricales, and the adductores pollicis. Lastly, it contributes to the nervous supply of the joints of the elbow, wrist, and hand. Median nerve. — The median nerve, composed of fibres proceeding from the lower three cervical and the first dorsal nerves, arises by two roots or heads, one from the outer, the other from the inner cord of the brachial plexus. Commencing by the union of these roots in front or on the outer side of the axillary artery, the nerve descends in contact with the brachial artery, lying on its antero-lateral aspect as far as the middle of the arm, then gradually passes inwards over it, and near the elbow gains the inner side of the vessel. Sinking into the hollow at the bend of the elbow, the nerve passes beneath the superficial portion of the pronator teres, but over the deep slip of that muscle, by which it is separated from the ulnar artery, and continues straight down the front of the forearm between the flexor sublimis and flexor profundus digitorum muscles. Arrived near the wrist it lies beneath the fascia, between the tendons of the flexor sublimis and palmaris longus internally and that of the flexor carpi radialis externally. It then enters the palm behind the annular ligament, and rests on the flexor tendons. Somewhat enlarged, and of a slightly reddish colour, it here separates into two parts of nearly equal size. One of these (the external) supplies some of the short muscles of the thumb, and gives digital branches to the thumb and the index finger ; the second portion supplies the middle finger, and in part the index and ring fingers. The median nerve usually gives no branch in the upper arm. A. Branches in the forearm. (a) Articular Iranches. — These are one or two filaments to the front of the elbow-joint (Riidinger). (1) Muscular Iranches arise either together or separately in the neighbourhood of the elbow and pass to the pronator teres (6 c\ flexor carpi radialis (6 c), palmaris longus and the condylo-ulnar head of the flexor sublimis digitorum (7, 8 c, Id). A separate offset enters the radial head of the flexor sublimis, and a third branch supplying the index finger belly of the same muscle is given off by the trunk at a lower level in the forearm. (c) Anterior interosseous nerve (7, 8 c, 1 d or 8 c, 1 d).— This is the longest branch of the median nerve, and it supplies the deeper muscles of the front of the forearm. Leaving the main trunk a little below the elbow, it runs downwards with the artery of the same name on the interosseous membrane to the deep surface of the pronator quadratus muscle, in which it ends. It distributes branches to the flexor longus pollicis and the outer half of the flexor profundus digitorum, between which it lies ; a slender branch is given off to the interosseous membrane, along or in which it descends, dividing into two, and supplying filaments to the membrane, to the anterior interosseous vessels, to the shafts of the radius and ulna with the medullary arteries, and to the periosteum ; and from the lower end of the nerve a twig is con- tinued to the front of the wrist-joint. Small Pacinian bodies are found on the branches passing to the bone and periosteum (Rauber). VOL, III., PT. 2. U 302 THE SPINAL NERVES. (d) The palmar cutaneous branch arises a variable distance above the wrist, and pierces the fascia of the forearm between the tendons of the flexor carpi radialis and palmaris longus, close to the annular ligament, to terminate in the integument of the palm, where it communicates with the palmar cutaneous branch of the ulnar nerve. Some filaments are distributed over the thenar eminence, and form com- munications with twigs of the radial or external cutaneous nerve. B. Branches in the hand. (a) Branch to muscles of the thumb. — This short nerve (6 c), arching outwards immediately below the annular ligament, subdivides into branches for the abductor, the opponens, and the outer head of the flexor brevis pollicis muscles. (#) Digital nerves. — These are five in number, and belong to the thumb, and the fingers as far as the outer side of the ring-finger. They lie at first beneath the superficial palmar arch and its digital branches, but as they approach the clefts between the fingers, they are close to the integument in the intervals between the longi- tudinal divisions of the palmar fascia, and on the fingers the nerves lie in front of the vessels. The first and second nerves lie along the sides of the thumb ; and the former (the outer one) is connected with the radial nerve over the border of the thumb. The third, destined for the radial side of the index finger, gives a branch to the first or most external lumbricalis muscle. The fourth supplies the second lumbricalis, and divides into collateral branches for the adjacent sides of the index and middle fingers. The fifth, the most internal of the digital nerves, is connected by a cross branch with the ulnar nerve, and divides to supply the adjacent sides of the ring and middle fingers. It often gives a branch to the third lumbricalis, which then has a double supply. Each digital nerve divides at the end of the finger into two branches, one of which supplies the ball on the fore part of the finger, while the other ramifies in the pulp beneath the nail. Branches pass from each nerve forwards and backwards to the integument of the finger ; those passing backwards join the dorsal collateral nerve, and supply mainly the integument over the second and third phalanges of the middle three digits. Filaments are also furnished to the articulations of the fingers. The volar digital branches of the median and ulnar nerves are beset with numerous Pacinian corpuscles both in the palm and on the fingers : the number of these bodies varies from 60 to 100 in each digit. Varieties. — Occasionally the median nerve does not receive any fibres from the first dorsal nerve. Either of the heads of the nerve may be double. The level at which the two heads join is very variable : they have been found separate to the middle of the arm, and in one case nearly as far as the elbow (Testut). Calori saw the two heads embracing the axillary vein as well as the artery. The inner head may cross behind, instead of in front of, the axillary artery. The whole nerve is often found passing- behind the brachial artery (Vol. II. p. 441). The outer head has been seen by Turner passing behind the axillary artery, so that the trunk of the nerve lay altogether to the inner side of the brachial artery ; and in another case recorded by the same anatomist the outer head separated from the musculo-cutaneous in the middle of the arm and crossed behind the brachial artery to join the inner head. Gruber and Walsh have described cases in which the nerve entered the forearm over the pronator teres muscle. It has also been seen running down the forearm superficial to the flexor sublimis digitorum (G. D. T.). The nerve has been found split for a certain distance in the forearm, the cleft giving passage to the ulnar artery (Testut) or a branch of that vessel (Mauclaire). or to the superficial long head of the flexor longus pollicis (Davies-Colley, Taylor and Dalton, J. W. Williams), or to a supernumerary long palmar muscle (Reid and Taylor). The frequent communication between the median and musculo-cutaneous nerves in the arm has already been referred to (p. 299). One instance is recorded of a connection between the median and ulnar nerves in the arm (p. 300). A communication between these nerves in the upper part of the forearm is present in the proportion of one in four or five limbs, usually THE MEDIAN NERVE. 303 in the form of a branch leaving- the median in common either with the muscular offsets at the elbow or with the anterior interosseous nerve, and passing- with or near the ulnar artery to join the ulnar nerve about the middle of the forearm : less frequently the connection is by means of a loop or small plexus, from which twigs are given off to the flexor profundus digitorum muscle : this communication between the median and ulnar nerves in the upper part of the forearm is normal in most apes (Hepburn, Hofer). and in lower mammals (Bardeleben). A communication in the lower part of the forearm is rare. In two cases a branch was seen passing from the median nerve at the elbow, over the superficial muscles, to join the ulnar (T. J. Jeans). Very seldom a branch runs from the ulnar to the median trunk or to its anterior interosseous branch. The communicating branch between the median and ulnar nerves in the palm is commonly directed from the ulnar to the median, but it may run in the opposite direction, or the communication may be looped or plexiform in arrangement. Absence of the communication has been noted. In two cases described by Klint the anterior interosseous nerve received a branch from the musculo-spiral (posterior interosseous ?) through the interosseous membrane. A communication between the anterior and posterior interosseous nerves at the lower end of the interosseous space is noticed by Martin and Rauber. (F. Curtis, " Recherches anatomiques sur Tanastomose du Median et du Cubital a 1'avant-bras," Intemat. Monatschr. f. Anat. u. Hist., iii, 1886 ; Third Annual Report of Committee of Collective Investigation of the Anat. Soc., by Arthur Thomson, Journ. Anat., xxvii, 1892.) The digital nerves in the palm are often pierced by the corresponding arteries. Four cases are recorded by Gruber in which the nerve supplying the adjacent sides of the middle and ring fingers arose from the trunk in the forearm. A branch from the median nerve to the abductor indicis muscle was observed by Brooks. SUMMARY. — The median nerve gives cutaneous branches to the palm, and to three and a half fingers. It supplies the pronator muscles, the flexors of the carpus and the long flexors of the fingers (except the ulnar flexor of the carpus, and part of the deep flexor of the fingers), likewise the outer set of the short muscles of the thumb, and two lumbricales. Articular filaments are also given to the joints of the elbow, wrist, and fingers. A great similarity will be observed in the distribution of the median and ulnar nerves. Neither gives any offset in the arm. Together they supply all the muscles of the front of the forearm and in the hand, and together they supply the skin of the palmar surface of the hand, and impart tactile sensibility to all the fingers. Musculo-spiral nerve. — The musculo-spiral nerve (n. radialis of French and German writers), the largest offset from the brachial plexus, is derived from the sixth, seventh, and eighth cervical nerves, in some cases also from the fifth. It occupies chiefly the back part of the limb, and supplies nerves to the extensor muscles, as well as to the skin. Arising behind the axillary vessels from the posterior cord of the brachial plexus, of which it is the principal continuation and the only branch prolonged into, the arm, it soon turns backwards with the superior profunda artery between the long and internal heads of the triceps, and runs beneath the external head of that muscle, in the hinder part of the spiral groove of the humerus, to the outer side of the arm. It then pierces the external intermuscular septum, and descends in the interval between the supinator longus and brachialis anticus muscles nearly to the level of the outer condyle of the humerus, where it ends by dividing into the radial and posterior interosseous nerves. Of these, the radial is altogether a cutaneous nerve, while the posterior interosseous is the muscular nerve of the back of the forearm. The branches of the musculo-spiral nerve may be classified according as they arise on the inner side of the humerus, behind that bone, or on the outer side. A. Internal branches. (a) Muscular branches for the long and inner heads of the triceps (7, 8 c). That for the inner head gives two or three filaments to the upper part of the muscle, and then descends by the side of the ulnar nerve, to which it is often closely adherent for a part of its course, and enters the lower short fibres of the head. This long filament is named by Krause the ulnar collateral branch. u 2 304 THE SPINAL NERVES. (&) The internal cutaneous branch of the musculo-spiral nerve (n. cutaneus brachii posterior) (8 c), often united in origin with the preceding, winds backwards beneath the intercosto-humeral nerve, and extends, supplying filaments to the skin over the long head of the triceps, nearly as far as the olecranon. This nerve is accompanied by a small cutaneous artery. B. Posterior branches. These consist of a fasciculus of muscular branches (7, 8 c) which supply the outer and inner heads of the triceps muscle and the anconeus. The branch of the anconeus is slender, and remarkable for its length ; it descends in the substance of the inner head of the triceps to reach its destination. C. External branches. (a) The external cutaneous branches, two in number, arise before the nerve pierces the external intermuscular septum, and become superficial just below the middle of the arm, between the outer head of the triceps and the brachialis anticus muscles. The upper branch (6 c), the smaller of the two, is directed downwards to the fore part of the elbow, along the cephalic vein, and distributes filaments to the lower half of the arm on its outer and anterior aspect. The lower branch (n. cutaneus antibrachii dorsalis) (6 c, or 6, 7 c, or 7 c, or 7, 8 c) descends in the interval between the external condyle and the olecranon, and reaches as far as the wrist, distributing its offsets to the lower half of the arm, and to the forearm, on their posterior aspect. It is connected near the wrist with a branch of the external cutaneous nerve, and often with the dorsal branch of the ulnar nerve. In some cases this branch is prolonged to the back of the hand (fig. 201, A). (b) Muscular branches are furnished to the supinator longus (6 c), extensor carpi radialis longior (6, 7 c) (the extensor carpi radialis brevior usually receiving its nerve from the posterior interosseous), and frequently a small twig to the outer part of the brachialis anticus (6 c), as the nerve lies between those muscles. Together with these branches articular filaments are given to the outer part of the elbow-joint. According to Rauber a branch of the musculo-spiral nerve is given regularly to the periosteum on the back of the humerus ; and in some cases it also furnishes the nerve to the shaft of that bone, when the principal medullary artery is derived from the superior profunda. Filaments are described as passing to the elbow-joint also from the ulnar collateral nerve, and from the branch to the anconeus. Varieties. — The musculo-spiral nerve has been seen passing backwards through the quadrilateral space between the teres muscles with the circumflex nerve (Guy's Hosp. Rep., xliv). A communication with the ulnar nerve in the arm is recorded by Villar (p. 300). The lower external cutaneous branch was traced by Brooks in one case to the first phalanx of the ring and the second phalanx of the little fingers ; and it has been observed furnishing the dorsal digital nerves of the little and the ulnar half of the ring fingers in the place of the ulnar nerve (Gruber, Gegenbaur). Radial nerve. — The radial nerve (ramus superficialis n. radialis) receives its fibres from the sixth cervical nerve, sometimes also the fifth or seventh. Continuing straight down from the musculo-spiral nerve, it lies a little to the outer side of the radial artery along the anterior border of the extensor radialis brevior, under cover of the supinator longus, and resting on the supinator brevis, the insertion of the pronator teres, and the radius. About three inches above the wrist the nerve turns backwards beneath the tendon of the supinator longus and becomes subcutaneous. It then divides into two branches, which ramify on the back of the hand in the following manner : — (a) The external portion passes to the radial side of the thumb, and is joined by an offset of the external cutaneous nerve. It distributes filaments over the thenar eminence. THE RADIAL NERVE. 305 (b) The internal portion communicates with the posterior branch of the musculo-cutaneous nerve in the forearm, sends an offset to the back of the wrist, which usually joins in an arch with the dorsal branch of the ulnar nerve, and then divides into four branches for the thumb and the outer two fingers. One Fig. 2'JO. VlKW OK THE RADIAL SIDE OF THE FOREARM, SHOWING THE FINAL DISTRIBUTION OF THE MUSCULO-SPIRAL NERVE. (Hirschfeld and Leveille.) J The supinator longus and the radial extensoi-s have been divided, and their upper parts removed ; the extensor coimnunis digitorum is pulled backwards, and the supinator bi-evis has been partially dissected to show the posterior interosseous nerve passing through it. 1, on the tendon of the biceps muscle, the musculo-cutaneous nerve ; 1', near the wrist, the lower part of this nerve and its plexus of union with the radial nerve ; 2, trunk of the musculo-spiral nerve in the interval between the. brachialis anticus, on which the number is placed, and the supinator longus muscles ; 2', its muscular twigs to the long supinator and long radial extensor ; 2", the posterior interosseous nerve passing through the substance of the supinator brevis ; 3, placed upon the cut lower portion of the supinator longus, and lower down, the radial nerve ; 4, the external digital nerve of the thumb ; 5, digital nerves of the forefinger and thumb arising in common ; 6, the same of the fore and middle fingers ; 7, twig of union with the dorsal branch of the ulnar nerve ; 8, placed upon the common extensor of the fingers, the muscular branches of the posterior interosseous nerve to the long extensor muscles ; 9, upon the extensor longus pollicifc, the branches to the short extensoi muscles. of these supplies the ulnar side of the thumb, the second passes to the radial side of the index finger, the third divides for the adjacent sides of the index and middle fingers, and the fourth is directed to the interspace between the middle and ring fingers. In their course these branches supply twigs to the skin of the outer part of the back of the hand ; and the innermost one crosses, and usually communicates with the outer branches of the dorsal uluar nerve. The distance to which the branches of the radial nerve extend varies in the several digits. On the thumb they reach to the nail, on the index finger to the second phalanx, and on the middle finger only to the first phalanx, while from the inner- most branch filaments pass to the root of the ring finger. From the dorsal digital nerves twigs are said to be given to the carpo-metacarpal, metacarpo-phalangeal, and first interphalangeal articulations ; and according to Hedon filaments pass forwards through the interosseous spaces to the skin of the palm. Lejars describes an offset from the outer division of the radial nerve to the abductor pollicis muscle (Bull. Soc. Anat. Paris, 1890, 433) Varieties. — The area of distribution of the radial and ulnar nerves, and the degree to which they overlap on the back of the hand, as well as the extent of the dorsal nerves on the three middle fingers, are subject to much variability. From observations in man and mammals Hedon and Zander conclude that the primitive arrangement is that in which the radial nerve supplies three and a half digits and the ulnar one and a half, all the digital branches extending to the nail. The reduction of the dorsal nerves on the three middle fingers appears to be an arrangement peculiar to man, in whom however the nerves are not unfrequently continued to the nail in the index and ring fingers, but very rarely in the middle finger. (H. St. John Brooks, '; On the distribution of the cutaneous nerves on the dorsum of the human hand/1 Internat. Monatschr. f. Anat. u. Phys., v. 1888 : E. Hedon. '• Etude critique sur rinnervation de la face dorsale de la main," Internat. Monatschr. f. Anat. u. Phys.. vi. 1889 ; R. Zander. •• Ueber die sensibeln Xerven auf der Riickenflache der Hand bei Saugetieren und beim Menschen.'' Anat. Anz.. iv. 1889.) 306 THE SPINAL NERVES. Occasionally the radial nerve supplies the whole of the back of the hand and fingers. Its outer division often gives a branch to the palm. Absence of the radial nerve was met with by Hepburn, the musculo-cutaneous supplying the thumb, and the ulnar nerve all the four fingers (Journ. Anat., xxi, 511). A. RADIAL- Fig. 201. — DORSAL CUTANEOUS NERVES OP THE HAND. (A, after Brooks ; B, after Hedon.) The radial nerve is shown in blue, the branches of the ulnar in red. offsets of the musculo-cutaneous, musculo-spiral and median in black. The two figures illustrate variations in the cutaneous supply. In A, the radial and ulnar nerves overlap to a considerable extent, and the lower external cutaneous of the musculo-spiral extends to the back of the hand. In B, the overlapping of the radial and ulnar nerves is slight, and the musculo-cutaneous is prolonged independently into the hand. Posterior interosseous nerve. — This nerve (r. profundus n. radialis), the larger of the two divisions of the musculo-spiral, is composed of fibres derived from the sixth and seventh, sometimes also the eighth, cervical nerves. It winds to the back of the forearm round the outer side of the radius, traversing the cleft in the supinator brevis muscle, and is prolonged between the deep and superficial layers of the extensor muscles to somewhat below the middle of the forearm, where it sinks beneath the long extensor of the thumb, and reaches the lower part of the interosseous membrane. Much diminished in size by the separation of numerous branches for the muscles, the nerve lies at the back of the wrist beneath the tendons of the extensor indicis and the common extensor of the fingers, and forms here a small enlargement, from which filaments are given to the adjoining ligaments arid articulations. Branches. — (a) Muscular branches.— Before the nerve passes to the back of the forearm it gives offsets to the extensor carpi radialis brevior (6, 7 c) and the supinator brev»s (6 c) muscles. After perforating the supinator brevis, it supplies branches (7 c) ANTERIOR PRIMARY DIVISIONS OF DORSAL NERVES. 307 to the extensor communis digitorum, extensor minimi digiti, extensor carpi ulnaris, the three extensors of the thumb, and the extensor indicis. (&) Articular branches. — From the terminal enlargement of the nerve fine twigs proceed to the articulations of the wrist, and, according to Rlidinger and Rauber, other filaments descend on the back of the hand to the metacarpo-phalangeal articulations. Varieties. — The posterior interosseous nerve may pass over, instead of perforating, the supinator brevis muscle (Luschka, Krause). A branch to the anconeus muscle is described by the same anatomists. There may be a communication between the anterior and posterior interosseous nerves at the lower part of the interosseous space (p. 303). In two cases, recorded by Turner and Schwalbe, the posterior interosseous nerve passed down to supply the adjacent sides of the index and middle fingers ; a similar condition has been found in the chimpanzee, orang and gibbon (Westling, Hepburn, Hofer). SUMMARY. — The musculo-spiral nerve supplies the extensor muscles of the elbow-joint, and frequently sends a filament to the brachialis anticus. which, however, receives its principal supply from another source. Before separating into its two large divisions, the nerve gives branches to two muscles of the forearm, viz., the long supinator, and the long radial extensor of the carpus. The posterior interosseous division distributes nerves to the remaining muscles on the outer and back part of the forearm, except the anconeus (previously supplied), viz., to the short supinator and the extensors. Cutaneous nerves are distributed, from the trunk of the nerve and its radial division, to the upper arm, to the forearm, and to the hand — on the posterior and outer aspect of each. Articular branches are furnished to the elbow, wrist, metacarpo-phalangeal, and first interphalangeal joints. DOESAL NERVES. The anterior divisions of the twelve dorsal or thoracic nerves are distributed almost entirely to the walls of the thorax and abdomen. The exceptions are the first, the greater part of which joins the brachial plexus, and the second and twelfth, which send cutaneous offsets to the arm and hip respectively. Close to the intervertebral foramina, these nerves are connected to the gangliated cord of the sympathetic by very short communicating branches ; they are then directed trans- versely outwards to their destination without forming any plexus, and in this respect they differ from the anterior primary divisions of the other spinal nerves. The smaller part of the first, and the trunks of the succeeding ten nerves pass forwards in the intercostal spaces, and are thence termed intercostal nerves. Of these, the upper six are confined to the parietes of the thorax, while the lower five are continued anteriorly from the intercostal spaces into the wall of the abdomen. The twelfth nerve, sometimes distinguished as the subcostal nerve, is placed below the last rib, and is therefore contained altogether in the abdominal wall. FIRST DORSAL NERVE. The anterior division of the first dorsal nerve divides into two parts, the larger of which ascends over the neck of the first rib to enter into the brachial plexus. The remaining portion of the nerve is continued as the first intercostal, a small branch which lies at first under cover of the first rib, and then courses along the first intercostal space, in the manner of the other intercostal nerves, but has usually no lateral cutaneous branch, and may also want the anterior cutaneous. Variety.— The first dorsal nerve frequently receives a connecting twig which passes up- wards in front of the neck of the second rib from the second nerve. This branch was found by Cunningham in twenty-seven out of thirty-seven dissections ; it was of variable size, but 308 THE SPINAL NERVES. generally very small, and it sometimes joined only one. in other cases both, of the divisions of the first nerve (Journ. Anat., xi, 539). UPPER OR PECTORAL INTERCOSTAL NERVES. In their course to the fore part of the chest, these nerves accompany the inter- costal blood-vessels. From the intervertebral foramina they are directed outwards in front of the superior costo-transverse ligaments, the levatores costarum and the external intercostal muscles, being covered anteriorly, as far as the angles of the ribs, only by the pleura and the thin layer of connective tissue known as the endothoracic fascia. Gaining the upper part of the corresponding intercostal spaces, where they are placed below the intercostal vessels, the nerves next run between the external and internal intercostal muscles, and soon give off the large lateral cutaneous branches, Fig. 202. — PLAN OP AN UPPER DORSAL NERVE. (G. D. T.) which accompany the prolongations of the trunks for a short distance, and then bend outwards through the ex- ternal intercostal muscles about mid- way between the spine and the sternum. The nerves themselves, much reduced in size, are now continued forwards amid the fibres of the internal intercostal muscles as far as the costal cartilages, where they again come into close relation with the pleura. In approaching the sternum they cross in front of the internal mammary vessels and the triangularis sterni ; and finally they pierce the internal intercostal muscles and the greater pectoral, to end in the integument of the breast, receiving the name of the anterior cutaneous nerves of the thorax. BRANCHES. — Muscular branches are furnished by the intercostal nerves in the first part of their course to the levatores costarum, and, from the upper four nerves, to the serratus posticus superior. Several twigs enter the intercostal muscles with which the nerves are in relation. At the fore part of the chest the triaogularis sterni is supplied by offsets of these nerves from the second or third to the sixth ; and from the fifth and sixth nerves branches pass to the upper end of the rectus abdominis. Minute subcostal branches perforate the internal intercostal muscles to reach the inner surface of the ribs, where they are distributed to the. periosteum and bone, as well as probably to the costal pleura (Testut) ; and, according to Luschka, fine sternal twigs are given off at the anterior ends of the intercostal spaces to the back of the sternum. The lateral cutaneous nerves of the thorax pierce the external intercostal and serratus magnus muscles, in a line a little behind the pectoral border of the axilla. The first intercostal usually gives no lateral branch, or only a slender twig to the axilla, but when that of the second nerve is unusually small, it may be supple- mented by a branch of the first. The branch from the second intercostal is named mtercosto-humeral, and requires separate description. Each of the remaining latera THE UPPER INTERCOSTAL NERVES. 309 cutaneous nerves divides into two branches, which reach the integument at a short distance from each other, and are named anterior and posterior. Fig. 203. — VIEW OF THE ANTERIOR DIVISIONS ov THE DORSAL AND SOME OF THK OTHER SPINAL NERVES FROM BEFORE. (HirscMeld and Leveille.) J The pectoralis major and minor muscles have been removed ; on the right side the rectus abdominis and internal oblique muscles are shown ; on the left side the anterior part of the rectus is cut away, and the transversalis is exposed. 1, median and other nerves of the brachial plexus ; 2, nerve of Wrisberg ; 3, intercosto-humei-al ; 4, intercostal nerves continued forwards to 4', their anterior cutaneous twigs ; 5, lateral cutaneous branches of these nerves ; 6, lateral cutaneous branch of the last dorsal nerve ; 7, iliac branch of the ilio- hypogastric nerve; 8, hypogastric branch of the same; 9, ilio-inguinal ; 10, middle cutaneous of the thigh. 310 THE SPINAL NERVES. The anterior branches are continued forwards over the border of the great pectoral muscle. In the female their terminal ramifications supply the skin over the mamma, and some filaments enter the substance of the gland. From the lowest two nerves twigs are supplied to the upper digitations of the external oblique muscle of the abdomen. The posterior branches turn backwards to the integument over the scapula and the latissimus dorsi muscle. The branch from the third nerve ramifies in the axilla, and a few filaments often reach the arm. The intercosto-humeral nerve (n. mtercosto-brachialis), the lateral cutaneous branch of the second intercostal nerve, corresponds with the posterior of the two divisions of the succeeding lateral cutaneous branches, the anterior being commonly wanting. It crosses the axillary space to reach the arm, and is connected in the axilla with an offset of the nerve of Wrisberg (p. 296). Penetrating the fascia, it becomes subcutaneous, and ramifies in the integument of the upper half of the arm on the inner and posterior aspect ; a few filaments reach the integument over the scapula. The branches of this nerve cross over the internal cutaneous offset of the musculo-spiral, and a communication is established between the two nerves. The size of the intercosto-humeral nerve, and the extent of its distribution, are in inverse proportion to the size of the other cutaneous nerves of the upper arm, especially the nerve of Wrisberg. The anterior cutaneous nerves of the thorax, which are the terminal twigs of the intercostal nerves, are reflected outwards in the integument over the great pectoral muscle. One or two of the upper branches may be connected with the supraclavicular nerves. In the female, those from the second, third, and fourth nerves are distributed over the mammary gland. Varieties. — At the hinder part or side of the chest some of the adjacent intercostal nerves are occasionally connected by filaments which cross the inner surfaces of the ribs, passing from one intercostal space to join the nerve in the interval next below. A twig' from the second intercostal nerve to the pectoralis major has been described by Swan and M. Flesch ; one to the pectoralis minor by Brooks. LOWER OR ABDOMINAL INTERCOSTAL NERVES. The lower intercostal nerves in the first part of their course have relations like those of the upper nerves already described. Lying between the external and internal intercostal muscles, they give off the lateral cutaneous branches, and at the fore part of the intercostal spaces they penetrate the internal intercostal muscles. They then pass between the slips of origin of the diaphragm, the seventh, eighth, and ninth nerves each crossing behind the cartilage of the rib below, and enter the abdominal wall. Here they are continued between the internal oblique and transversalis muscles as far as the outer edge of the rectus, diverging from one another as they pass inwards, in consequence of the increasing obliquity of the lower nerves. Finally, perforating the posterior layer of the sheath of the rectus, they turn forwards through the substance of that muscle and the anterior layer of its sheath to end in small cutaneous branches (anterior cutaneous nerves) . While between the abdominal muscles the lower three or four nerves are united by loops of com- munication, and sometimes form a small plexus. BRANCHES. — Muscular branches are given to the levatores costarum, to the serratus posticus inferior (from the ninth, tenth, and eleventh nerves), to the subsostal and intercostal muscles, and to the abdominal muscles with which the nerves are in contact. Filaments are also described as passing from these nerves to the costal portion of the diaphragm (Baur, Swan, Luschka). The lateral cutaneous nerves of the abdomen pass to the integument through the external intercostal and external oblique muscles, in a line with the corresponding THE LAST DORSAL NERVE. 311 nerves on the thorax, and divide in the same manner into anterior and posterior branches. The anterior IrancJws are the larger. They supply the digitations of the external oblique muscle, and are then directed inwards, the lower nerves also inclining downwards, in the superficial fascia, with small cutaneous arteries, nearly to the edge of the rectus muscle. The posterior branches bend backwards over the latissimus dorsi. The anterior cutaneous nerves of the abdomen are uncertain in number and position. There are generally two or three twigs from each nerve, and some of them perforate the rectus near its outer border, but the greater number issue near the linea alba. The branches of the seventh nerve emerge near the lower end of the ensiform process, and those of the tenth usually supply the skin about the umbilicus. LAST DOBSAL NERVE. The anterior primary division of the last dorsal nerve is directed outwards in company with the abdominal branch of the first lumbar artery along the lower border of the twelfth rib. It passes beneath the external arched ligament of the diaphragm, across the front of the quadratus lumborum, and at the outer border of the latter muscle it perforates the posterior aponeurosis of the transversalis (middle layer of the lumbar fascia), to follow a course similar to that of the lower intercostal nerves in the abdominal wall. It is usually connected near its origin with the first lumbar nerve by means of a small cord, which descends on or through the substance of the quadratus lumborum muscle. It supplies branches to the quadratus lumborum (frequently), internal oblique, transversalis, rectus, and pyramidalis muscles, as well as lateral and anterior cutaneous branches ; and it sometimes com- municates in the abdominal wall with the ilio-hypogastric nerve. Its anterior cutaneous twigs are distributed below a point midway between the umbilicus and pubis. The lateral cutaneous branch of the last dorsal nerve is usually of considerable size. It pierces the internal oblique muscle, gives a branch to the lowest slip of the external oblique, and then emerging through the latter muscle a variable distance (from one to three inches) above the iliac crest, is directed downwards to the integument of the fore part of the gluteal region, some filaments reaching as far as the great trochanter. Varieties. — In some cases the lateral cutaneous branch of the last dorsal nerve is small, and is distributed entirely to the skin above the iliac crest, its place over the hip being taken by the iliac branch of the ilio-hypogastric nerve. Complete absence of this branch was observed by M. Griffin four times in fifty cases (" Some Varieties of the Last Dorsal and First Lumbar Nerves," Journ. Anat., xxvi, 1891). LUMBAR NEEVES. The anterior divisions of the lumbar nerves increase in size from the first to the fifth. The upper three and the greater part of the fourth enter the lumbar plexus ; the smaller part of the fourth and the fifth pass down to the sacral plexus. On leaving the inter vertebral foramina, the nerves are connected by filaments with the cord of the sympathetic, these filaments being longer than those connected with other spinal nerves, in consequence of the position of the lumbar sympathetic ganglia on the fore part of the bodies of the vertebrae. In the same situation small twigs are furnished to the quadratus lumborum muscle from the first and, sometimes, the second nerve, and to the psoas from the second and third nerves. 312 THE SPINAL NERVES. LUMBAR PLEXUS. The lumbar plexus is formed by the anterior primary divisions of the upper four lumbar nerves. It is placed in the substance of the psoas muscle, in front of the transverse processes of the corresponding vertebrae. Above, the plexus is narrow, and is usually connected with the last dorsal nerve by a small offset from that nerve, DXTT IV V CJ Fig. 204. — DIAGRAM OF THE LUMBAR AND SACRAL PLEXUSES WITH THE PRINCIPAL NERVES ARISING FROM THKM. (Allei) Thomson.) % DXII, the divided roots of the last dorsal nerve ; LI, to V, the roots of the five lumbar nerves ; the loops uniting the an- terior primary divisions of these nerves together, and the first with the twelfth dorsal, are shown ; SI, to V, and CI, the sacral and coccygeal nerves ; p, placed on some of the nerves, marks the posterior primary divisions cut short ; p, p', the plexus formed by the union of the posterior branches of the third, fourth, and fifth sacral and the coccygeal nerves ; d, anterior divi- sion of the last dorsal nerve, from which d' the lateral cutaneous branch arises ; 1,1', ilio-hypogastric nerve, dividing into its two branches ; the ilio-inguinal nerve is seen below these, without a number ; 2, genito- crural ; 2', external cutaneous of the thigh ; ql, branches to quadratus lumborum ; %.s, branches to the psoas muscle ; a; anterior crural nerve ; il, branches to the iliacus ; ob, obturator nerve ; ob', accessory obturator ; IV, V, loop from the fourth and fifth lumbar, forming the lumbo-sacral cord ; 3, superior gluteal nerve ; sc, great sciatic nerve, continued from the sacral plexus ; 4, small sciatic nerve rising from the plexus posteriorly ; 4', inferior gluteal nerve ; 5, inferior pudendal ; 5', posterior cutaneous of the thigh and leg ; 6, 6, branch to the obturator internus and gemellus superior ; b", (>', branch to the gemellus inferior, quadratus femoris and hip-joint ; 7, twigs to the pyriformis ; 8, pudic nerve ; 9, visceral branches ; 9', twig to the levator ani ; 10, perforating cutaneous nerve; 11, coccygeal branches. named dor so-lumbar ; below, it is wider, and is joined to the sacral plexus by means of a branch passing from the fourth lumbar nerve to the fifth. The nerves entering the lumbar plexus do not form an interlace- ment, as in the brachial plexus, but the several nerves of distribution proceeding from the plexus for the most part arise by two or more roots from a corre- sponding number of spinal nerves, so as to produce the appearance of a series of loops. The usual arrangement may be thus stated : — The first lumbar nerve, having been joined by the branch from the last dorsal, gives off the ilio- hypogastric and ilio-inguinal nerves, and sends downwards a communicating branch to the second nerve. The fibres of the dorso-lurnbar cord enter chiefly the ilio-hypogastric nerve, but some may pass also to the ilio-inguinal. The THE LUMBAR PLEXUS. 313 descending branch of the first nerve contributes to the genito-crural, often to the anterior crural, and occasionally to the obturator nerve. The second lumbar nerve furnishes the greater part of the genito-crural and external cutaneous nerves, and gives a connecting branch to the third, from which some of the fibres of the anterior crural and obturator nerves are derived. From the third nerve three branches proceed ; the largest part enters the anterior crural nerve ; a small branch, dorsally placed, joins the external cutaneous ; and the third, arising from the ventral aspect of the trunk, passes to the obturator nerve. The fourth nerve also gives three branches, of which the anterior and posterior serve to complete the obturator and anterior crural nerves respectively, while the third, placed below the others, descends to join the fifth lumbar nerve, thus forming the Iwnbo-sacral cord, which enters into the sacral plexus. The BRANCHES of the lumbar plexus form two sets, which are distributed, one to the lower part of the wall of the abdomen, the other to the fore part and inner side of the lower limb. In the former set are the ilio-hypogastric and ilio-inguinal nerves, and part of the genito-crural ; and to the latter belong the remaining part of the genito-crural nerve, the external cutaneous, the obturator, and the anterior crural nerves. Varieties of the lumbar plexus. — In the normal condition, the first three lumbar nerves enter wholly into the lumbar plexus, and the fifth lumbar nerve into the sacral plexus, while the fourth — the nervus fur calls of v. Jhering — is divided between the two plexuses. The proportion of the fourth nerve, which descends to the sacral plexus, is normally less than one- half, but it varies in different cases from one-twentieth to nine-tenths (Eisler). When the sacral division of this nerve is very large it may be joined by a branch from the third lumbar nerve ; and conversely, when the sacral division of the fourth nerve is very small, the fifth lumbar nerve may send an offset to the lumbar plexus, where it contributes to the formation of the anterior crural and obturator nerves, or, perhaps, only to the former. In these cases there are, therefore, two furcal nerves, viz., 3 I and 4 I, or 4 1 and 5 1 respectively. Farther, the sacral branch of the fourth lumbar nerve may be wanting, and then the fifth lumbar is the sole furcal nerve. A series may thus be traced in which the furcal nerves are progressively, from above downwards, 3 and 4 I, 4 I, 4 and 5 Z, and 5 I. At the same time, the nerves given off to the limb from the lumbar and sacral plexuses are found to vary in their origin to some extent, having a tendency to arise higher or lower, according to the position of the furcal nerve or nerves. In the slighter degrees of variation this is shown by a difference in the size of the contributing roots, so that a given trunk will derive a larger share of its fibres from an upper, and a smaller share from a lower spinal nerve, or vice versa ; but in the more marked degrees the origin may be shifted upwards or downwards to the extent of one spinal nerve. There are thus to be distinguished two extreme forms of plexus (fig. 205), which may be called Ugh and low (the " anterior " and "posterior " forms of Langley, " prefixed " and " postfixed types " of Sherrington), and between which the normal or average plexus is placed, as is shown, for the lumbar plexus only, in the following table, wherein the order of the nerves in each case indicates the size of the roots in descending series, and the roots enclosed in parentheses are inconstant : — High form. Normal form. Low form. External cutaneous ... 2, (1)1 3, 2, 4, 1 1 2, 31 3, 4, 2 I 3, 2Z 4, 3, 5, 21 Anterior crural Furcal nerves (very rarely 3, 2, 1 I) 3, 2, 4, 11, (12 d) 3 and 4 1 (or 4 I with large sacral division) 4, 3, 2, 1 I 41 4, 3, 5, 2 1 4 and 5 1, or 51 Forms intermediate to these also occur : and the relations of the several offsets of the plexus to one another sometimes vary to a limited extent : that is, one nerve may have a high origin, while the others belong to the normal form, or vice versa. Variations are more frequent and extensive in the downward direction than the opposite. In some instances the extreme forms are associated with irregularities of the vertebral column (see Vol. II, p. 12), 314 THE SPINAL NERVES. the low form of plexus with an additional moveable vertebra, and the high form with assimi- lation of the fifth lumbar vetebra to the sacrum, but this is not always the case. The upper three offsets of the lumbar plexus, not being1 true limb-nerves, do not vary so much in their PUOJ Fig. 205. — EXTREME FORMS OF LUMBAR AND SACRAL PLEXUSES. (From Eisler.) A. High form of plexus : ventral aspect. From a subject in which the fifth lumbar vertebra was assimilated to the sacrum, and articulated on both sides with the ilium. B. Low form of plexus : dorsal aspect. From a subject in which there were thirteen dorsal and five lumbar vertebrae. origin, although they also are affected at times by the general form of the plexus ; on the other hand, it may happen with a low form of plexus that the ilio-hypogastric and ilio- inguinal nerves receive an additional root from the twelfth dorsal (Paterson) . (J. N. Langley (lumbar plexus of cat), Journ. Phys.. xii. 349, xv. 210. and xvii. 296 ; C. S. Sherrington (cat and monkey), Journ. Phys.. xiii. 639 ; P. Eisler. " Der Plexus lumbosacralis des Menschen," Halle, 1892 ; A. M. Paterson, " The Origin and Distribution of the Nerves to the Lower Limb," Journ. Anat., xxviii, 84). Ilio-hypogastric and ilio-iiiguinal nerves. — These nerves are the upper two branches of the lumbar plexus. They are both derived mainly from the first lumbar nerve, and have a nearly similar course and distribution, corresponding together to the anterior (intercostal) division of a dorsal nerve. They pass forwards between and through the broad muscles of the abdomen, furnish a lateral cutaneous branch to the integument of the hip, and becoming subcutaneous anteriorly, end in the integument of the lowest part of the abdomen and scrotum in the male, or labium pudendi in the female, as well as the adjacent part of the BRANCHES OF LUMBAR PLEXUS. 315 thigh. The extent of distribution of the one is inversely proportional to that of the other. The ilio-hypogastric nerve, the highest and largest of the branches proceed- ing from the first lumbar nerve, usually receives fibres also from the last dorsal nerve through the dorse-lumbar cord. Issuing from the upper part of the psoas muscle at the outer border, it runs obliquely over the quadratus lumborum to the iliac crest, and there perforating the transverse muscle of the abdomen, gets between that muscle and the internal oblique, and divides into an iliac and a hypogastric branch. (a) The iliac branch (ramus cutancus lateralis) pierces the internal oblique muscle, and then emerges through the external oblique close to the iliac crest about the junction of its middle and anterior thirds, to be distributed to the integument over the gluteus medius and tensor vaginae femoris muscles. (b) The hypogastric or abdominal branch passes on between the transversalis and internal oblique muscles, to both of which it supplies twigs, and is connected with the ilio-inguinal nerve near the iliac crest. It then perforates the internal oblique muscle, and, piercing the aponeurosis of the external oblique a little above the external abdominal ring, is distributed to the skin of the abdomen above the pubis (r. cutaneus anterior). Varieties. — The ilio-hypogastric nerve is occasionally derived from the last dorsal, and it may even receive a root from the eleventh dorsal nerve (fig-. 205, A). The iliac branch varies in size inversely with the lateral cutaneous of the twelfth dorsal, and it is sometimes altogether wanting-. The hypogastric branch is not unfrequently joined with the last dorsal nerve between the muscles. In some cases this branch supplies the pyramidalis muscle. The ilio-inguinal nerve, smaller than the preceding, is also derived from the first lumbar nerve, and sometimes receives an accession from the dorso-lurnbar cord. Appearing from beneath the outer border of the psoas muscle below the ilio-hypo- gastric nerve, it is directed obliquely downwards and outwards over the quadratus lumborum and iliacus to the fore part of the iliac crest, where it perforates the transversalis, and communicates with the ilio-hypogastric nerve between the muscles. Then piercing the internal oblique muscle, it descends in the inguinal canal, and emerging at the external abdominal ring on the outer side of the spermatic cord, divides into branches which are distributed to the skin of the pubic region and root of the penis and scrotum in the male, or labium pudendi in the female (nn. scrotales s. labiales anteriores), and of the adjacent upper and inner part of the thigh. In its progress this nerve may furnish branches to the internal oblique and transversalis muscles. Varieties. — The ilio-hypogastric and ilio-inguinal nerves often arise by a common trunk, which divides after perforating the transversalis muscle. The ilio-inguinal nerve is occasion- ally derived from the last dorsal nerve (fig. 205, A). On the other hand, it may spring from the loop between the first and second lumbar nerves, or even entirely from the latter nerve. It is sometimes small, and ends near the iliac crest by joining the ilio-hypogastric nerve, which in that case gives off an inguinal branch having a similar course and distribution to the ilio-inguinal nerve. The ilio-inguinal nerve may be absent, its place being taken by the genital, rarely by the crural, branch of the genito-crural. In some cases the nerve has an iliac or lateral branch, which is distributed to the skin in the neighbourhood of the anterior superior iliac spine. The ilio-inguinal nerve may also replace to a greater or less extent the genital branch of the genito-crural. or (very rarely) the external cutaneous -nerve (M. Griffin). Genito-crural nerve. — The genito-crural nerve (n. geniiofemoralis) belongs partly to the external genital organs and partly to the thigh. It is derived chiefly from the second lumbar nerve, but receives also a few fibres from the connecting cord between that and the first nerve. The nerve descends obliquely through the psoas muscle, from which it emerges near the inner border, about on a level with 316 THE SPINAL NERVES. the disc between the third and fourth lumbar vertebrae, and then lying on the fascia covering the anterior surface of that muscle divides at a variable height into an internal or genital, and an external or crural branch. It often bifurcates close to Fig. 206. — VIEW FROM BEFORE OF THE ANTERIOR BRANCHES OF THE LUMBAR AND SACRAL NERVES WITH THE PLEXUSES. (From Sappey, after Hirschfeld and Leveille.) £ 1, lumbar part of the sympathetic cord ; 2, 2', anterior primary division of the twelfth dorsal nerve ; 3, first lumbar ; 4, 4', ilio-hypogastric branch of this nerve ; 5, 5', ilio-inguinal branch ; 6, second lumbar nerve ; 7, 7', genito-crural nerve ; 8, 8', external cutaneous nerve of the thigh ; 9, third lumbar nerve ; 10, fourth ; 11, fifth ; 12, lumbo-sacral cord ; 13, iliac branch of the ilio-hypogastric ; 14, its abdominal branch ; 15, ilio-inguinal nerve ; 16, external cutaneous nerve of the right side passing out of the abdomen under Poupart's ligament ; 17, 17, 17, cutaneous ramifications of this nerve ; 17', the same nerve exposed on the left side ; 18, 18', genital branch of the geuito-crural ; 19, 19, its crural branch on the right side ; 19', the same on the left side exposed as it descends in front of the femoral artery ; 20, 20', anterior crural nerve ; 21, 21', obturator nerve ; 22, left sacral plexus ; 23, aortic plexus of the sympathetic, connected with the other preaortic plexuses and the lumbar ganglia. its origin from the plexus, in which case its two branches perforate the psoas muscle in different places. (a) The genital 'branch (n. spermaticus externus) lies upon or near the external iliac artery, and sends a filament along that vessel ; then perforating the trans- versalis fascia (or passing through the deep abdominal ring) it traverses the inguinal canal with the spermatic cord, supplies the cremaster muscle, and sends filaments to the skin of the scrotum and adjoining corner of the thigh. In the female it accompanies the round ligament of the uterus to the skin of the groin. (b) The crural branch (n. lumboinguinalis) descends upon the psoas muscle beneath Poupart's ligament into the thigh. Immediately below that ligament, and THE EXTERNAL CUTANEOUS NERVE. 317 at the outer side of the femoral artery, it pierces the fascia lata, and supplies the skin on the upper part of the thigh, communicating with the middle cutaneous branch of the anterior crural nerve. While it is passing beneath Poupart's ligament, some filaments are prolonged from this nerve on the femoral artery. Varieties. — The two divisions of the genito-crural nerve often arise independently from the lumbar plexus (fig-. 205). The genital branch is occasionally derived from the last dorsal and first lumbar nerves (fig-. 205, A). Either branch may proceed wholly from the first or the second lumbar nerve (fig. 205, B). Absence of either division, or more rarely of the whole nerve, may occur : in such cases the fibres usually forming the genital branch are associated with the ilio-inguinal nerve, and those belonging to the crural division with the external cutaneous or anterior crural nerve. Conversely, the genital branch may reinforce or replace the ilio-inguinal nerve, and the crural branch the external or middle cutaneous. The genital branch often gives filaments to the lower fibres of the internal oblique and transversalis muscles. External cutaneous nerve. — This nerve (n. cufaneus femoris lateralis), arising from the second and third lumbar nerves, emerges from the outer border of the psoas muscle, and crosses the iliacus below the ilio-inguinal nerve, where it is placed beneath the iliac fascia. It passes under Poupart's ligament, and enters the thigh immediately below the anterior superior iliac spine, where it divides into an anterior and a posterior branch distributed to the integument of the outer side of the hip and thigh (fig. 208, 1). (a) The posterior branch perforates the fascia lata and subdivides into two or three others, which turn backwards and supply the skin upon the outer surface of the limb, from the upper border of the hip-bone nearly to the middle of the thigh. The highest among them are crossed by the cutaneous branches from the last dorsal nerve. (Z>) The anterior branch, the continuation of the nerve, is at first contained in a canal formed in the substance of the fascia lata ; but, about four inches below Poupart's ligament, it enters the subcutaneous fatty tissua, and is distributed along the outer part of the front of the thigh, ending near the knee. The principal offsets spring from its outer side. In some cases, this branch reaches quite down to the knee, and takes part there in the formation of the patellar plexus. Varieties. — In the normal form of lumbar plexus the external cutaneous nerve is derived mainly from the second lumbar nerve, and receives only a small root from the third. In the high form of plexus it arises entirely from the second lumbar nerve, or from the second and first ; while in the low form its chief root is furnished by the third nerve. The external cutaneous nerve often accompanies, or is united with, the anterior crural trunk to below Poupart's ligament. The posterior branch is sometimes replaced by an offset of the genito- crural nerve. In one instance the place of the external cutaneous nerve was taken by a branch of the ilio-inguinal (M. Griffin). Obturator nerve. — The obturator nerve arises from the lumbar plexus generally by three roots, which proceed from the second, third and fourth lumbar nerves, and of which that from the third is the largest, while the root from the second nerve is often very small. Having emerged from the inner border of the psoas muscle, opposite to the brim of the pelvis, it runs along the side of the pelvic cavity, above the obturator vessels, as far as the opening in the upper part of the thyroid foramen, through which it escapes from the pelvis into the thigh. In the foramen, it divides into an anterior and a posterior branch, which are separated from one another by some fibres of the obturator externus, and lower down by the short adductor muscle. A. The anterior or superficial portion communicates with the accessory obturator nerve, when this is present, and descends over the upper border of the obturator VOL. III., PT. 2. X 318 THE SPINAL NERVES. externus and in front of the adductor brevis, but behind the pectineus and adductor longus muscles. It gives branches as follows : — (a) An articular branch to the hip-joint arises in the thyroid foramen. (ft). Muscular branches are given to the gracilis and adductor longus muscles, and generally also to the adductor brevis. (c) The terminal twig turns outwards upon the femoral artery, and surrounds that vessel with small filaments. (d) An offset at the lower border of the adductor longus communicates beneath the sartorius with the internal cutaneous branch of the anterior crural nerve, and with a branch of the internal saphenous nerve, forming a sort of plexus. B. The posterior or deep part of the obturator nerve, having perforated the upper Fig. 207.— THE LUMBAR PLEXUS FROM BEFORE. WITH THE DISTRIBUTION OF SOME OF ITS NERVES. (Slightly altered from Schmidt.) i «, last rib ; b, quadratus lumborum muscle ; c, oblique and ti-ansverse muscles, cut near the crest of the iliimi and turned down : d, pubis ; c, adductor brevis muscle ; /, pectineus divided and turned out- wards ; 41 4 I and 51 or 5 I N. to quad, fern N. to obt. int Internal popliteal Superior gluteal division) ) 4, 51 1 *, 5. 4 1, 2 s Is, 5, 41, 2 s, (3 I) 5, 4 ', 1 s 4, 5 Z, 1 s 51, 1, 2s 1 «, .H 2s, 41, 3s 51, I s 41, (2 s) Is, 51 2, 1, 3 s 2, 1 s, 5 1, 3 s, (4 511 2s 0 Inferior gluteal N. to pyriformis External popliteal . ... 51, Is, 41 (50, 1, 2s 5, 41, 1 s, (3 Z) Is, 51, 2s I, 2s 51, 1 s 41 2s 1, 2s, 51 2, 1, <3)s 1 2s 51 (3s] Small sciatic Pudic 1, 2s, 51 2, 3, 1 s, il 2, 3, 1 s 3. 4, 2. 1 s 2, 3, 4 s 3421s (The relative size of the several roots is indicated by the order of the nerves, and those included in parentheses are inconstant.) A. — COLLATERAL BRANCHES. Small muscular branches.— The pyriformis muscle is supplied by twigs arising from the back of the first angl second sacral nerves. The nerve of the quadratus f emoris muscle arises from the front of the upper part of the plexus, receiving its fibres from the lumbo-sacral cord and first sacral nerve. Concealed at first by the great sciatic nerve, it passes beneath the gemelli and the tendon of the obturator internus — between those muscles and the capsule of the hip-joint, — and reaches the deep (anterior) surface of the quadratus. It gives off a branch to the inferior gemellus muscle, and another to the back part of the hip-joint. A second filament frequently passes directly from the sacral plexus to the articulation. The nerve of the obturator internus muscle, derived from the fifth lumbar and upper two sacral nerves, springs from the front of the plexus immediately below the fore- going, with which it is usually connected at its origin. Appearing at t ie lower border of the pyriformis to the inner side of the great sciatic nerve, it then turns over the ischial spine on the outer side of the pudic vessels, and is directed forwards through the small sacro-sciatic foramen to reach the inner surface of the obturator muscle. This nerve furnishes a small offset to the superior gemellus. Varieties. — Occasionally the branch to the superior gemellus is also given off by the nerve to the quadratus ; or that muscle may be supplied from both sources. In one instance J. T. Wilson found the nerve to the quadratus continued to the upper part of the adductor magnus (Journ. Anat., xxiii, 354). Superior gluteal nerve. — The superior gluteal nerve arises from the back of the lumbo-sacral cord and first sacral nerve. It leaves the pelvis with the gluteal 326 THE SPINAL NERVES. vessels through the great sacro-sciatic foramen above the pyriformis muscle, and immediately divides into two branches, which run forwards between the glutens medius and minimus, supplying those muscles and the tensor vaginas femoris. (a) The upper branch is the smaller and more superficial ; it sends its offsets solely to the glutens medius. (b) The lower branch crosses the middle of the gluteus minimus muscle with the lower branch of the gluteal artery ; it sends branches to both the gluteus medius and minimus, and generally perforates the fore part of the latter muscle to reach the deep surface of the tensor vaginas femoris, in which it ends. Varieties. — The superior gluteal sometimes receives fibres also from the second sacral nerve. A branch to the pyriformis muscle may be given off from the lowest root of this nerve. Fig. 211.— BRANCHES OF THE SACRAL PLEXUS IN THE BUTTOCK. (Hirschfeld and Leveille.) i a, great trochanter ; i, tensor vaginne femoris muscle ; c, tendon of the obturator interims muscle ; d, upper part of the vastus externus ; e, coccyx ; /, gracilis muscle; between/and dr the adductor magnus, semitendinosus, and biceps muscles, with the lower end of the gluteus maximus ; 1, 1. upper branch of the superior gluteal nerve ; 1', 1', inferior branch of the same nerve ; 1", branch of the nerve to the tensor vaginae femoris ; 2, 2, sacral plexus and great sciatic nerve ; 2', muscular twig from the plexus to the pyri- formis; 2" branch to the gemellus superior and obturator internus; 3, small sciatic nerve, 3', 3', placed on the upper and lower parts of the divided gluteus maximus, the branches of the inferior gluteal nerve ; 3", the gluteal cutaneous branches of the small sciatic nerve winding round the lower border of the gluteus maximus ; 4, the continuation of the small sciatic nerve as posterior cutaneous nerve of the thigh ; 4', inferior pudendal branch of the small sciatic ; 5, placed on the lower part of the sacral plexus points to the origin of the pndic nerve ; 6, its pei^neal division with its muscular branches ; 6', internal superficial perineal branch ; 6", external superficial perineal ; -t- +, distribution of these nerves and the inferior pudendal on the scrotum ; 7, dorsal nerve of the penis. Inferior gluteal nerve. — The inferior gluteal nerve arises from the back of the plexus, being formed of fibres which are derived from the lumbo-sacral cord, the first and second sacral nerves. It usually sends a branch downwards to join the commencement of the small sciatic nerve, and sometimes the two nerves are more closely connected at their origins. The inferior gluteal nferve turns backwards at the lower border of the pyriformis muscle, and immediately divides into a number of branches which, diverging upwards and downwards, enter the deep surface of the gluteus maximus muscle about midway between its origin and insertion. Small sciatic nerve. — The small sciatic nerve (nervus cutaneus femoris posterior) is entirely a sensory nerve, supplying the integument of the lower part of the buttock, the back of the thigh, and the upper part of the back of the leg ; it also furnishes one branch to the perineum — the inferior pudendal nerve. The nerve takes its origin usually from the back of the upper three sacral nerves by as many roots, the highest of which arises in common with a part of the inferior gluteal nerve. Emerging below the -pyriformis muscle, it descends beneath the gluteus maximus muscle, resting on the great sciatic nerve, and then along the back of the thigh under cover of the fascia lata to a little beyond the knee. Here it becomes subcutaneous, and its terminal ramifications are distributed to the skin of THE SMALL SCIATIC NERVE. the calf, one branch accompanying the short saphenous vein and forming a com munication with the external saphenous nerve. Fig. 212. — POSTERIOR CUTANEOUS NERVES OF THE HIP AND THIGH. (Hirschfeld and Leveille.) | ' a, gluteus maximus muscle, divided at its inferior part to show the small sciatic nerve ; b, b, fascia lata ; c, d, part of the semitendinosus, biceps, and semimembranosus muscles exposed by the removal of the fascia ; e, gasti'ocnemius ; /, coccyx ; g, internal saphenous vein ; 1, 2, 3, 3, posterior twigs of the external cutaneous nerve of the thigh ; 4, small sciatic nerve ; 4', 4", its gluteal cutaneous branches ; 5, continuation of the small sciatic ; 5', 5', its inner and outer femoral cutaneous branches spreading on the fascia of the thigh ; 6, 6, its terminal branches descending on the calf of the leg ; 7, internal and external popliteal nerves, separating in the popliteal space ; 8, posterior divisions of the lower sacral and coccygeal nerves ; 9, inferior pudendal nerve. Fig. 213. — DEEP POSTERIOR NERVES OF THE HIP AND THIGH. (Hirschfeld and Leveille.) £ a, gluteus medius muscle ; b, gluteus maximus ; c, pyriformis ; d, placed on the great trochanter, points to the tendon of the obturator internus ; e, upper part of the femoral head of the biceps ; /, semi- tendinosus ; if, semimembranosus: h, gastrocnemius ; i, popliteal artery; 1, placed on the gluteus minimus muscle, points to the superior gluteal nerve ; 2, 2, 2, ramifications of the inferior gluteal nerve ; 3, placed on the great sacro-sciatic ligament, points to the pudic nerve ; 3', its farther course ; 4, inferior pudendal ; f>, placed on the upper divided part of the semitendinosus and biceps, points to the divided small sciatic or posterior cutaneous nerve of the thigh ; 6, great soiatic nerve ; 6', 6', some of its muscular branches to the hamstrings ; 7, internal popliteal nerve ; 7', its muscular or sural branches ; 8, external popliteal nerve ; 8', its external cutaneous branch ; 9, communicating tibial ; 9', communi- cat'.ng peruneal branch to the external saphenous nerve. Branches. — (a) The gluteal cutaneous branches (mi. clunium mferiores) are two or three in number, and bend upwards over the lower border of the gluteus maximus muscle, to be distributed to the skin of the lower and outer part of the gluteal region. 328 THE SPINAL NERVES. (b) The inferior pudendal nerve (rr. perineales] turns inwards below the ischial tuberosity, giving offsets (sometimes separate branches of the nerve) to the skin ot the upper and inner part of the thigh, and is continued forwards to the outer part of the scrotum (or external labium pudendi), where its terminal filaments are distributed, after forming communications with the external superficial perineal branch of the pudic nerve. (c) The femoral cutaneous branches are numerous, and arise from both sides of the nervj while it lies beneath the fascia : they supply the skin of the back of the thigh, the larger number passing to the inner side. Varieties. —In cases of separate origin of the internal and external popliteal nerves (p. 324), the small sciatic nerve also arises from the sacral plexus in two parts. The ventral portion descends with the internal popliteal nerve below the pyrif ormis. and gives off the inferior pudendal and inner femoral branches, while the dorsal portion passes through that muscle with the external popliteal nerve, and furnishes the gluteal and outer femoral branches. The inferior pudendal nerve sometimes pierces the great sacro-sciatic ligament. The small sciatic may be joined on the back of the thigh by a branch of the great sciatic nerve (p. 331). In some cases the small sciatic nerve ends behind the knee, its place in the leg being then taken by a branch of the external popliteal (p. 336). . The perforating cutaneous nerve (fig. 215, 10) is a slender branch which arises most frequently from the second and third sacral nerves, and passes backwards through the great sacro-sciatic ligament : it then turns upwards round the lower border of the glutens maximus, and is distributed to the skin over the inner and lower part of that muscle. Varieties. — A perforating cutaneous nerve arising as above stated was found by Eisler 22 times in 34 plexuses : in three of these it was conjoined at its origin with the pudic nerve. Instead of piercing the great sacro-sciatic ligament it may run with the pudic nerve between the great and small ligaments, or it may pass between the great ligament and the gluteus maximus muscle. In other cases a nerve having a similar distribution («. jwrfontHx <•!><•<• t/i/nix major. Eisler) arises from the third and fourth (fig. 210), or fourth and fifth nerves (fig. 204. 10), and pierces the coccygeus muscle on its way backwards. Its place may also be supplied by a branch of the small sciatic. B. — TERMINAL BRANCHES. Pudic nerve. — The pudic nerve (n. pudendus) is a short plexiform trunk, .which is given off from the lower part of the sacral plexus, and distributes branches to the perineum and external organs of generation. Its chief root is usually derived from the third sacral nerve. To this are added others from the fourth and second nerves ; and according to Eisler it also receives fibres from the first sacral nerve. The upper roots spring from the front of the ventral divisions of the corresponding sacral nerves. Passing out of the pelvis between the pyriformis and coccygeus muscles, it turns forwards over the attachment of the small sacro-sciatic ligament to the ischial spine, where it is placed on the inner side of the pudic vessels, to the small sacro- sciatic foramen. Having thus arrived at the hinder part of the ischio-rectal fossa, the trunk ends by dividing into the following three branches, viz., the inferior hsemorrhoidal nerve, the perineal nerve, and the dorsal nerve of the penis, or clitoris, according to the sex. (a) The inferior hcemorrhoidal nerve (4, 3, (2) s) is sometimes derived separately from the sacral plexus ; it inclines inwards towards the anus and divides into numerous branches which supply the skin of the hinder part of the perineal space and the external sphincter muscle. The most anterior branches form communica- tions with the interior pudendal and superficial perineal nerves. (b) The perineal nerve (3, 2, 4 s) is the largest of the three divisions of the pudic nerve. It runs forwards along the outer wall of the ischio-rectal fossa, being con- THE PUDIC NERVE. 329 tained in a special sheath of the obturator fascia below the pudic vessels, and breaks up into superficial and deep branches. The superficial 'perineal nerves are two in number, external and internal. The external or posterior, which is the first to leave the perineal trunk, runs forwards along the outer side of the perineal space to the scrotum, and sometimes gives a branch to the adjacent part of the thigh. The iniernal or anterior branch is larger, and runs forwards nearer the middle line, dividing into long slender offsets which are distributed to the integument of the scrotum. The two branches communicate freely together, and the external generally receives the connecting filaments from the inferior pudendal and inferior haemorrhoidal nerves. The superficial perineal and Fig. 214. — RIGHT SIDE OP THE INTERIOR OP THE MALK PELVIS, WITH THE PRINCIPAL NKRVES DISPLAYED. (Hhschfeld and Le- veille.) i The left wall has been removed as far as the sacrum behind and the symphysis pubis in front ; the viscera and the lower part of the right levator ani have been removed ; a, lower end of the aorta ; a', placed on the fifth lumbar vertebra, between the two common iliac arteries, of which the left is exit short ; b, right external iliac vessels ; c, symphysis pubis ; d, the divided pyriformis muscle, close to the left auricular surface of the sacrum ; e, bulb of the urethra covered by the bulbo-cavernosus muscle ; the membranous part of the urethra cut short is seen passing into it ; 1, on the crest of the ilium, the external cutaneous nerve of the thigh passing over the iliacus muscle ; 2, on the psoas muscle, the genito-crural nerve ; 3, obturator nerve ; 4, 4, on the lumbo-sacral cords ; that of the right side points to the gluteal artery cut short ; 4'. superior gluteal nerve ; 5, on the right sacral plexus, points by four lines to the anterior divisions of the four ' upper sacral nerves, which, with the lumbo-sacral cord, form the plexus ; 5', placed on the fifth piece of the sacrum, points to the fifth sacral nerve ; 5", visceral branches from the third and fourth sacral nerves ; 6, placed on the lower part of the coccyx, below the coccygeal nerves ; 7, the nerve of the levator ani muscle ; 8, inferior hsemorrhoidal nerve ; 9, nerve of the obturator internus ; 10, pudic nerve : 10', muscular branches of the perineal nerve ; 10", superficial perineal nerves, and on the scrotum the distribution of these nerves and the inferior pudendal nerve ; II, right dorsal nerve of the penis ; 11', the nerve on the left crus penis which is cut short ; 12, small sciatic nerve; 12', its inferior pudendal branch. ; 13, on the transverse process of the fifth lumbar vertebra, the lowest lumbar sympathetic ganglion ; 14, on the first piece of the sacrum, the upper sacral sympathetic ganglia ; between 14 and 6, are seen the remaining ganglia and sympathetic nervous cords, as well as their union with the sacral and coccygeal nerves, and at 6, the lowest ganglion or ganglion impar. inferior pudendal nerves are sometimes named from their distribution long scrotal nerves (nn. scrotales poster iores). In the female, both the superficial perineal branches terminate in the external labium pudendi (nn. labiales posterior es). The deep branches generally arise by a single trunk, and are distributed mainly to the muscles of the perineum. They supply the fore part of the external sphincter and levator ani muscles, the transversus perinei, ischio-cavernosus and bulbo- cavernosus. One branch passes inwards through the bulbo-cavernosus muscle, and divides into slender filaments which penetrate the corpus spongiosum and reach the mucous membrane of the urethra. (c) The dorsal nerve of the penis (2, 3, (1) s) is the deepest branch of the pudic nerve, and accompanies the pudic artery in its course through the deep perineal fascia (Vol. II, pp. 339 and 477), and between the layers of the suspensory liga- 330 THE SPINAL NERVES. inent to the dorsum of the penis, alons; which it passes as far as the glans, where it divides into filaments for the supply of that part. While passing through the deep perineal fascia, it gives fine twigs for the supply of the constrictor urethras muscle ; and on the dorsum of the penis, it is joined by branches of the sympathetic system, and sends outwards numerous offsets to the integument on the upper surface and sides of that organ. Some filaments also penetrate the corpus cavernosum. In the female the dorsal nerve of the clitoris is much smaller than the correspond- ing branch in the male ; it is similarly distributed. Fig. 215. — DISSECTION OP THE PERINEUM OF THE MALE TO SHOW THE DISTRIBUTION OF THE PUDIC AND OTHER NERVES. (Hirschfeld and Leveille. ) | On the right side a part of the gluteus maximus muscle and the great sacro-sciatic ligament have been removed : 1, great sciatic nerve of the right side ; 2, 2', on the right side, inferior gluteal nerve ; 2", on the left side, gluteal cutaneous branches of the small sciatic ; 3, small sciatic nerve in the thigh ; 4, 4, inferior pudendal nerve ; 4', network of this and the superficial perineal nerves in the scrotum ; 5, right pudic nerve ; 6, superior branch or dorsal nerve to the penis : 7, external superficial perineal branch ; 7', internal superficial perineal branch ; 8, deep or musculo-bulbal branches ; 9, inferior hsemorrhoidal nerve ; 10, perforating cutaneous nerve. Varieties. — In the high, form of plexus the pudic nerve may receive fibres from the fifth lumbar (Eisler). Henle describes and figures a root to the pudic from the fifth sacral nerve, but this was never met with by Eisler or Paterson. The inferior hsemorrhoidal nerve often pierces the great or the small sacro-sciatic ligament on its way to the perineum (Eisler). The external superficial perineal nerve may also pierce the great sacro-sciatic ligament. SUMMARY. — The pudic nerve supplies the skin and muscles of the perineum, the penis, and part of the scrotum in the male ; and the clitoris, labia, and other corre- sponding parts in the female. It communicates with the inferior pudendal branch of the small sciatic nerve. Great sciatic nerve. — The great sciatic nerve (nervus ischiadicus'), the largest nerve in the body, supplies the muscles at the back of the thigh, and by the branches continued from it gives nerves to all the muscles below the knee and to the greater part of the integument of the leg and foot. The several joints of the lower limb receive filaments from it and its branches. This large nerve is the continuation of the main part of the sacral plexus. It extends from the lower border of the pyriformis muscle to somewhat below the middle of the thigh, where it separates into two large divisions, named the internal and external popliteal nerves. At first it lies in the hollow between the great THE GREAT SCIATIC NERVE. 331 trochanterand the ischial tuberosity, covered by the gluteus maximus and resting on the gemelli, obturator internus, and quadratus femoris muscles, in company with the- small sciatic nerve and the sciatic artery, and receiving from that artery a branch which runs for some distance in its substance. Lower down it rests on the adductor magnus, and is covered behind by the loug head of the biceps muscle. f Branches. — In its course downwards, the great sciatic nerve supplies offsets to the hamstring muscles, viz., the semitendinosus, two heads of the biceps, and semimembranosus. A branch is likewise given to the inner part of the adductor magnus. The branches of the great sciatic nerve to the muscles arising from the ischial tuberosity are associated with its internal popliteal division, from which, however, they may be separated up to their origin from the sacral plexus. They are then found to arise in the following^ order from above downwards : — the nerves to the adductor magnus (from 4 and 5 Z) and semimembranosus (4, 5J and 1 *)> these being- commonly united in one cord ; two branches for the semitendinosus (from 5 /, 1 and 2 xj, one supplying- the part of the muscle above, and the other the part below the tendinous inscription ; and the nerve of the long head of the- biceps (from 1, 2 and 3 *). The nerve of the short head of the biceps is united with the external popliteal division, and according to Paterson may be followed up to 5 I, 1 and 2 s. Varieties. — The bifurcation of the great sciatic nerve may take place at any point intermediate between the sacral plexus and the lower part of the thigh ; and in some cases the two popliteal nerves arise separately from the sacral plexus (see p. 324). Very rarely the division takes place below the popliteal space (Henle). A branch of the great sciatic to join the small sciatic on the back of the thigh is said to be normal by Krause, of frequent occurrence by Henle. In one instance a nerve to the short head of the biceps arose directly from the sacral plexus in union with the inferior gluteal nerve (G-. D. T.). Internal popliteal nerve. — The internal popliteal (n. tibialis), the larger of the two divisions of the great sciatic nerve, following the same direction as the parent trunk, continues along the middle of the popliteal space to the lower border of the popliteus muscle, beyond which point the continuation of the trunk receives the name of posterior tibial. The internal popliteal nerve lies at first at a considerable distance from tfye popliteal artery, at the outer side and nearer to the surface ; but, from the km e-joint downwards, the nerve, continuing a straight course, is close behind the artery, and then crosses it rather to the inner side. Branches. — The internal popliteal nerve supplies branches to the knee-joint and to the muscles of the calf of the leg, and also part of a cutaneous branch, the external or short saphenous nerve. „ (a) The articular branches are given off from the upper part of the popliteal trunk, and are generally three in number ; two of them accompany the upper and lower articular arteries of the inner side of the knee-joint, the third follows the middle or azygos artery. These nerves pierce the ligamentous tissue of the joint. The upper one is often wanting. (b) The muscular branches arise from the nerve while it is contained in the popliteal space. They include two nerves to the gastrocnemius (1, 2 s) — one to each head of the muscle ; a small nerve to the plantaris (4, 5 /, 1 s), derived either from the branch to the outer head of the gastrocnemius, or directly from the main trunk ; a considerable branch to the soleus (57, 1, 2 s), which enters the muscle on its posterior aspect, close to the upper border ; and a nerve to the popliteus (4, 5 /, Is). The last branch arises somewhat lower down, and is more deeply placed, than the others ; it descends on the outer side of the popliteal vessels, gives off filaments to the superior tibio-fibular articulation, to the tibia, and to the interosseous membrane, and then turns beneath the lower border of its muscle, which it penetrates on the deep or anterior surface. The branch to the tibia enters the shaft of the bone with the medullary artery : that to the interosseous membrane is a long slender 3o~ THE SPINAL NERVES. which, after supplying filaments to the anterior and posterior tibial arteries, is •continued downwards in the membrane to end in the inferior tibio-fibular articu- lation, and the periosteum of the lower part of the tibia ; small Pacinian corpuscles occur on the filaments passing to the bone and ligaments. (c) The cutaneous branch. — External or short saphenous nerve (n. suralis). — The cutaneous branchof the internal popliteal nerve (tibial communicating nerve ; n. cutaneus •sunv medialis) (1, 2 s) descends along the leg, in the furrow between the heads of the Fi<:. 216. — POSTERIOR CUTANEOUS NERVES OF THE LEG. after Hirschfeld and Leveille.) (From Sappey, 1, internal popliteal nerve ; 2, branch to the inner head of the gastro- cnemius muscle ; 3, 4, branches to the outer head and plantaris ; 5, tibial communicating nerve ; 6, external popliteal nerve ; 7, lateral cutaneous branch of the leg ; 8. peroneal communicating branch, descending to unite with the tibial communicating in 9, the external saphenous nerve ; 10, calcaneal branch from this nerve ; 11, calcaneal and plantar cutaneous branches from the posterior tibial nerve ; 12, internal saphenous nerve ; 13, posterior branches of this nerve. gastrocnemius muscle, to about midway between the knee and the foot. Here it perforates the fascia, and a little lower down is usually joined by a branch from the external popliteal nerve (peroneal communicating}. After receiving this communicat- ing branch, the external saphenous nerve descends beneath the integument near the outer side of the tendo Achillis in company with the short saphenous vein, and turns forwards below the external malleolus to end in the skin on the outer side of the little toe, forming also a communication on the dorsum of the foot with the outer division of the musculo- cutaneous nerve. While turning round the external malleolus, the extern H! saphenous nerve gives off external calcaneal branches to the skin on the outer side of the heel ; and other filaments pass to the ankle-joint and the astragalo- calcaneal articulation (Riidinger), Varieties. — The union between the tibial communicating nerve and the branch of the external popliteal nerve occurs in some cases higher than usual, occasionally even at or close to the popliteal space. It sometimes happens that the com- munication between the nerves is altogether wanting ; in which case the cutaneous nerve to .he foot is generally continued from the branch of the internal popliteal nerve. The area of distribution of the external saphenous nerve in the foot is often increased, so that it supplies in part or wholly the outer one and a half, or even two and a half toes on their dorsal aspect : in these cases the peroneal communi- cating branch is said to be of larger size than usual. Occasionally the external saphenous nerve ends on the outer border of the foot, without reaching the toes. Posterior tibial nerve. — The internal popliteal nerve receives the name of posterior tibial at the lower margin of the popliteus muscle. It passes down the leg with the posterior tibial artery, lying for a short distance on the inner side of the vessel and afterwards on the outer side, the artery inclining inwards from its origin while the nerve takes a straighter course. In the interval between the inner malleolus and the heel, it divides into the two plantar nerves (internal and external). The posterior tibial nerve, like the accompanying vessels, is covered at first by the muscles of the calf of the leg, afterwards only by the integument and fascia, and it rests upon the deep-seated muscles. THE INTERNAL PLANTAR NERVE. 333 Branches. — The deep muscles on the back of the leg, the fibula, the integument of the sole of the foot, and the ankle-joint receive branches from the posterior tibial nerve in its course along the leg. (a) The muscular branches (5 /, 1, 2 s) emanate from the upper part of the nerve either separately or by a common trunk ; one is distributed to each of the deep muscles, viz., the tibialis posticus, the flexor longus digitorum, and the flexor longus hallucis ; and a second nerve is furnished to the soleus, piercing the deep surface of the muscle. (&) The fibular branch is a long slender offset which arises in common with the nerves to the deep muscles, and descends, beset with numerous Pacinian corpuscles, in the canal of the peroneal vessels as far as the ankle. It gives off filaments to the vessels which it accompanies, to the shaft of the fibula with the medullary artery, and to the periosteum covering that bone (Rauber). (c) The calcaneo-plantar nerve (1, 2s) is given off by the posterior tibial in the lower part of the leg, and becomes superficial by piercing the internal annular ligament. It divides into internal calcaneal branches which ramify in the integu- ment on the inner side of the heel, said. plantar cutaneous branches which supply the skin of the inner and hinder part of the sole. (a) One or two articular filaments pass from the posterior tibial nerve close above its division to the inner side of the ankle-joint (Rudinger). Internal plantar nerve. — The internal plantar (4, 5 /, Is), slightly the larger of the two nerves to the sole of the foot into which the posterior tibial divides, accompanies the internal or smaller plantar artery, and supplies nerves to both sides of the inner three toes, and to one side of the fourth. From the point at which it separates from the posterior tibial nerve, it is directed forwards under cover of the first part of the abductor of the great toe ; then passing between that muscle and the short flexor of the toes, it gives off the internal collateral branch for the great toe, and divides about the middle of the foot into three digital branches. The outermost of these branches communicates with the external plantar nerve. The distribution of this nerve in the foot closely resembles that of the median nerve in the hand. Branches.— (a} Muscular branches are supplied to the abductor hallucis and flexor brevis digitorum. (b) An articular filament passes deeply between the abductor hallucis and the tendons of the long flexors of the toes to supply the joints between the astragalus, the navicular, and the inner two cuneiform bones (Rudinger). (c) Small plantar cutaneous branches perforate the plantar fascia to ramify in the integument of the sole of the foot. (d) The digital branches are named numerically from within outwards : the outer three pass from under cover of the plantar fascia near the clefts between the toes. The first or innermost branch continues single, but the other three bifurcate to supply the adjacent sides of two toes. They are distributed as follows : — Theirs/ digital branch is destined for the inner side of the great toe ; it becomes subcutaneous farther back than the others, and sends off a branch to the flexor brevis hallucis muscle. The second branch, having reached the interval between the first and second metatarsal bones, furnishes a small twig to the first lumbricalis muscle, and bifurcates behind the cleft between the great toe and the second to supply their contiguous sides. The third digital branch, corresponding with the second interosseous space, divides in a manner similar to that of the second branch into two offsets for the sides of the second and third toes. VOL. III., PT. 2. Y 334 THE SPINAL NERVES. The fourth digital branch, distributed to the adjacent sides of the third and fourth toes, usually has a communication with the external plantar nerve. Along the sides of the toes, cutaneous and articular filaments are given from these digital nerves ; and, opposite the ungual phalanx, each sends a dorsal branch to the pulp beneath the nail, and then runs on to the ball of the toe, where it is distributed like the nerves of the fingers. Pacinian corpuscles are attached at intervals to these nerves. External plantar nerve. — The external plantar nerve (1, 2s) completes the supply of digital nerves to the toes, furnishing branches to the little toe and half the fourth ; it also gives a deep branch of considerable size, which is distributed to several of the short muscles in the sole of the foot. There is thus a great resemblance between the distribution of this nerve in the foot and that of the ulnar nerve in the hand. Fig. 217. — SUPERFICIAL AND DEEP DISTRIBUTION OK THE PLANTAR NERVES. (After Hirschfeld and Leveille, slightly modified.) (Allen Thomson.) ^ Parts of the flexor brevis digitoruin, abductor hallucis, abductor minimi digiti, and the tendons of the flexor longus digitorum, together with the lumbricales muscles, have been removed so as to bring into view the adductor transversus and interosseous muscles in the middle of the foot. a, upon the posterior extremity of the flexor brevis digitorum, near which, descending over the heel, are seen ramifications of the calcaneal branch of the posterior tibial nerve ; b, abductor hallucis ; c, tendon of the flexor longus digitorum, divided close to the place where it is joined by the flexor accessorius ; d, abductor minimi digiti ; e, tendon of the flexor longus hallucis between the two portions of the llexor brevis hallucis ; 1, internal plantar nerve giving twigs to the abductor hallucis, and 1', a branch to the flexor brevis digitorum, cut short ; 2, inner branch of the internal plantar nerve, giving branches to the flexor brevis hallucis, and forming 2', the internal collateral nerve of the great toe ; 3, continuation of the internal plantar nerve, dividing into three branches, which form, 3', 3', 3', the plantar digital nerves of the first and second, second and third, and third and fourth toes ; 4, external plantar nerve ; 4', its branch to the abductor minimi digiti ; 5, twig of union between the plantar nerves ; 6, superficial branch of the external plantar nerve, dividing into 6', 6', the collateral digital nerves of the fourth and fifth toes and the external nerve of the fifth ; 7, deep branch of the external plantar nerve. The external plantar nerve runs obliquely forwards towards the outer side of the foot, along with the external plantar artery, between the flexor brevis digitorum and the flexor accessorius, as far as the interval between the former muscle and the abductor of the little toe. Here it divides into a superficial and a deep branch, having previously furnished offsets to the abductor minimi digiti and the flexor accessorius, as well as a filament through the last muscle to the calcaneo-cuboid articulation (Riidinger). (a) The superficial portion separates into two digital branches, which have the same general arrangement as the digital branches of the internal plantar nerve. The outermost of these is undivided, and runs along the outer side of the little toe : it is smaller than the other, and pierces the plantar fascia farther back. The short flexor muscle of the little toe, and sometimes one or both of the interosseous muscles of the fourth space, receive branches from this nerve. The larger digital branch usually communicates with the internal plantar nerve, and bifurcates near the cleft between the fourth and fifth toes to supply one side of each. (I) The deep or muscular part of the external plantar nerve dips into the sole of the foot with the external plantar artery, under cover of the tendons of the flexor THE EXTERNAL PLANTAR NERVE. 335 muscles and the accessorius, and terminates in numerous branches for the following muscles : — all the interosseous (dorsal and plantar) except occasionally one or both of those in the fourth space, the outer three lumbricales, the adductor transversus and adductor obliquus hallucis. This part of the nerve also furnishes articular filaments to the tarso-metatarsal, and frequently to the metatarso-phalangeal joints, us well as minute perforating branches, which pass upwards through the posterior ends of the intermetatarsal spaces to join the interosseous branches of the anterior tibial nerve (Riidinger). Out of ten dissections by Brooks, the lumbricales were supplied as stated above in nine. In the tenth case the first and second lumbricales received branches from both the internal and Fig. 218. — CUTANEOUS NERVES OF OUTER SIDE OF THE LEG AND FOOT. (From Sappey, after Hirschfeld and Leveille. ) £- 1, external popliteal nerve ; 2, its lateral cutaneous branch ; 3, pcroneal communicating branch which unites with 4, the tibial communicating, in 5, the external saphenous nerve ; 6, calcaneal branch of the external saphenous ; 7, external dorsal digital branch of the fifth toe ; 8, dorsal digital branch of the fourth and fifth toes ; 9, 9, musculo-cutaneous nerve ; 10, 10, its two divisions ; 11, union with the external saphenous ; 12, communication between its outer and inner branches ; 13, anterior tibial nerve, shown by the removal of a part of the muscles ; 14, its inner ter- minal branch, emerging in the space between the first and second toes, where it gives the collateral dorsal digital branches to their adjacent sides ; 15, recurrent articular nerve. external plantar nerves (Journ. Anat.. xxi, 575). The branch of the external plantar nerve to the second lumbricalis runs forwards beneath the adductor transversus hallucis, and then turns backwards over that muscle to reach its destina- tion. Cruveilhier describes the branch to the third lumbricalis as piercing- the adductor trans- versus hallucis. The deep part of the external plantar nerve rarely gives a branch to the outer head of the flexor brevis hallucis (normal accord- ing1 to Henle and Schwalbe). SUMMARY OF THE INTERNAL POPLITEAL NERVE. — This nerve supplies all the muscles of the back of the leg and sole of the foot, the articulations of the kuee, ankle and foot, the bones and vessels of the leg, and the in- tegument of the plantar aspect of the toes, the sole of the foot, and in part that of the lower half of the back of the leg. External popliteal or peroueal nerve (n.peronceus communis]. — This nerve descends obliquely along the outer side of the popliteal space, lying close to the biceps muscle. Continuing downwards over the outer part of the gastrocnemius muscle (between it and the biceps) and below the head of the fibula, the nerve turns round that bone and, passing between it and the peroneus longus muscle, divides into the anterior tibial and the musculo-cutaneous nerves. BRANCHES. — Some articular and cutaneous branches are derived from the external popliteal nerve before its final division. (a) The articular branches are conducted to the outer side of the capsular liga- ment of the knee-joint by the upper and lower articular arteries of that side. They Y 2 336 THE SPINAL NERVES. sometimes arise together, and the upper one occasionally springs from the great sciatic nerve before the bifurcation. From the lower branch a filament is given to the superior tibio-fibular articulation (Eiidinger). From the place of division of the external popliteal nerve, a branch (often double) called the recurrent articular nerve ascends through the tibialis anticus with the anterior tibial recurrent artery ; its fibres terminate mainly in that muscle, but fila- ments may be traced to the superior tibio-fibular articulation, the periosteum over the outer tuberosity of the tibia, and the fore part of the knee-joint. (b) The cutaneous branches (5 /, 1, 2 s), generally two in number, supply the skin on the back part and outer side of the leg. The peroneal or fibular communicatiny branch, which usually joins the short saphenous nerve below the middle of the back of the leg, is the largest of these nerves. In some instances, it continues as a separate branch, and its cutaneous filaments reach down to the heel or on to the outer side of the foot. The lateral cutaneous branch of the leg (n. cutaneus sune laterals), often arising in conjunction with the foregoing, extends along the outer side of the leg to the middle or lower part, sending offsets both backwards and forwards. In some cases there is another cutaneous branch which arises from the upper part of the external popliteal nerve, and ramifies over the back of the calf, taking the place of the small sciatic nerve below the knee. Musculo -cutaneous nerve. — The musculo-cutaneous nerve (n.peronceussuper- ficialis) (4, 5 /, Is) descends between the peronei muscles and the long extensor of the toes, and reaches the surface by perforating the fascia in the lower part of the leg on the anterior aspect. It then divides into two branches, distinguished as external and internal, which proceed to the toes. The two branches sometimes perforate the fascia at different spots. Branches. — (a) Muscular branches are given to the peroneus longus and peroneus brevis. (b) Cutaneous branches given off near the primary division are distributed to the lower part of the leg. (c) The internal branch of , the musculo-cutaneous nerve, passing forwards along the dorsum of the foot, furnishes one branch to the inner side of the great toe, and another to the contiguous sides of the second and third toes. It also gives offsets which extend over the inner ankle and side of the foot. This nerve communicates with the long saphenous nerve on the inner side of the foot, and with the anterior tibial nerve between the first and second toes. (d) The external branch, smaller than the internal, descends over the foot towards the fourth toe, tvhich, together with the contiguous borders of the third and fifth toes, it supplies with branches. Cutaneous nerves, derived from this branch, spread over the outer ankle and the outer side of the foot, where they are connected with the short saphenous nerve. The dorsal digital nerves are continued on to the last phalanges of the toes. The number of toes supplied by each of the two divisions of the musculo- cutaneous nerve is liable to vary ; together, these nerves commonly supply all the toes. on the dorsal aspect, excepting the outer side of the little toe, which receives a branch from the short saphenous nerve, and the adjacent sides of the great toe and the second toe, to which the anterior tibial nerve is distributed : with this latter branch, however, it generally communicates. Varieties. — The external division of the musculo-cutaneous nerve is often reduced in size, the deficiency being supplied by the external saphenous nerve. Less frequently the internal branch is replaced to a greater or lets extent en the toes by the anterior tibial nerve. The THE ANTERIOR TIBIAL NERVE. 337 number of toes supplied by the musculo-cutaneous nerve is seldom increased. (On variations in the nerves of the dorsum of the foot, and their relative frequency, see the Second Annual Report of the Committee of Collective Investigation of the Anat. Soc.. by Arthur Thomson , Joura. Anat., xxvi, 1891.) Anterior tibial nerve. — The anterior tibial nerve (n. peroneus profundus) (4, 5 /, 1 s\ commencing between the fibula and the peroneus longus, inclines obliquely beneath the long extensor of the toes to the fore part of the interosseoua membrane, and there comes into contact with the anterior tibial vessels ; with these vessels it descends to the front of the ankle-joint, where it divides into an external and an internal branch. The nerve reaches the anterior tibial artery about Fig. 219. — DISTRIBUTION OP THE BRANCHES OP THE EXTERNAL POPLITEAL NERVE ON THE FRONT OP THE LEG AND DORSUM OP THE FOOT. (After Hirschfeld and Leveille.) 1 The upper part of the peroneus longus muscle has been removed, the tibialis anticus, the long extensor of the great toe and the peroneus longus are drawn apart in the leg by hooks marked a, b, and c, and the tendons of the extensor muscles have been removed on the dorsum of the foot ; 1, external popliteal or peroneal nerve, winding round the outer part of the fibula ; 1', its recurrent articular branches exposed by the dissection of the upper part of the tibialis anticus muscle ; 2, 2, musculo-cutaneous nerve ; 2' 2', twigs to the long and short peroneal muscles ; 3, 3', internal branch of the musculo-cutaneous nerve ; 4, 4', 4', its external branch ; 5, external saphenous nerve, uniting at two places with the outer branch of the musculo-cutaneous ; 5', its branch to the outer side of the fifth toe ; 6, placed on the upper part of the extensor longus digitorura, marks the anterior tibial nerve passing beneath the muscle ; 6, placed farther down on the tendon of the tibialis anticus, points to the nerve as it lies in front of the anterior tibial artery ; 6', 6', its muscular branches in the leg ; 6", on the tendon of the extensor longus hallucis, points to the anterior tibial nerve after it has passed into the foot behind that tendon ; 7, its inner branch, uniting with a twig of the musculo-cutaneous, and giving the dorsal digital nerves to the adjacent sides of the first and second toes ; 8, distribution of its outer branch to the extensor brevis digitorum and tarsal articulations. the junction of the upper with the second fourth of the leg, and is thence placed in front of the vessels as far as the ankle, at which spot it is usually on their outer side. Branches. — (a) Muscular branches. — In its course along the leg, the anterior tibial nerve gives offsets to the adjacent muscles, namely, the tibialis anticus, the extensor longus digitorum, the extensor proprius hallucis, and the peroneus tertius. (b) An articular filament for the ankle-joint arises from the lower part of the nerve. (c) The external branch of the anterior tibial nerve turns outwards over the tarsus beneath the short extensor of the toes ; and, having become enlarged (like the posterior interosseous nerve on the wrist) breaks up into branches which supply the short extensor muscle, and the articulations of the foot. (d) The internal branch, continuing onwards in the direction of the anterior tibial nerve, accompanies the dorsal artery of the foot to the first interosseous space, and ends in two branches, which supply the integument on the neighbouring sides of the great toe and the second toe on their dorsal aspect. It communicates with the internal division of the musculo-cutaneous nerve. From the internal branch one, and from the external two or three slender interosseous branches are sent forwards to the intermetatarsal spaces, where they are joined by the perforating twigs of the external plantar nerve (p. 385). They supply, 338 THE SPINAL NERVES. filaments to the tarso-metatarsal articulations and the periosteum of the metatarsal bones, and terminate in the metatarso-phaiangeal joints. The second and some- times the first of these nerves give twigs also to the dorsal interosseous muscles upon which they lie (Riidinger, Cunningham). Varieties. — Occasionally the anterior tibial nerve supplies also the inner side of the great toe, or the adjacent sides of the second and third toes. In one case the anterior tibial nerve sent branches to the outer three and a half toes, the great toe and the inner half of the second being- supplied by the musculo-cutaneous (F. T. Roberts. Liverpool Med. and Surg-. Reports, vi. 1867). Very rarely the digital branches are altogether wanting. SUMMARY OF THE EXTERNAL POPLITEAL NERVE. — This nerve supplies, besides articular branches to the knee, ankle, and foot, the muscles and integument of the outer side and front of the leg and dorsum of the foot. It gives the peroneal communicating branch to the short saphenous nerve, and communicates with the long saphenous nerve. SYNOPSIS OF THE SENSORY DISTRIBUTION OF THE CEREBRO-SPINAL NERVES. 1. In the head. — The face, and head in front of tlie ear are supplied with sensory nerves from the fifth cranial nerve. The ophthalmic division supplies branches to the forehead, upper eyelid, and dorsum of the nose. The superior maxillary division supplies the greater part of the cheek, the side of the nose, upper lip, lower eyelid, and the region behind the eye over the fore part of the temporal fascia. The inferior maxillary division supplies the chin and lower lip, the hinder part of the cheek, the fore and upper parts of the pinna of the ear on its outer side, and the integument in front of the ear and upwards on the side of the head. The head behind the ear is mainly supplied by the great occipital branch of the posterior division of the second spinal nerve, but above the occipital protuberance there is also distributed the branch from the posterior division of the third spinal nerve ; and in front of the area of the great occipital nerve is a space supplied by anterior divisions of spinal nerves, viz., the back of the pinna of the ear, and the lower part of its outer surface, together with the integument behind, and that in front over the parotid gland, which are supplied by the great auricular nerve (2, 3 c) ; while between the area of this nerve and the great occipital the small occipital nerve (2, 3 c) reaches the scalp, and sends a branch to the upper part of the pinna. The auricular branch of the pneumo-gastric nerve also is distributed on the back of the ear. Cavities of the head. — The mucous membrane of the nasal fossa is supplied by the olfactory nerves and the first and second divisions of the fifth nerve. The ramifications of the olfactory nerves are restricted to the small olfactory region at the highest part of the cavity; the nasal branch of the ophthalmic division of the fifth nerve supplies the anterior portion of the lining membrane; and the superior maxillary serves all the remainder. The frontal sinus is supplied by the nasal nerve, the ethmoidal cells and sphenoidal sinus by the nasal and superior maxillary, and the maxillary antrum by the superior maxillary nerve. In the mouth, the upper lip, the teeth of the upper jaw with the gum, and the mucous membrane of the hard palate, are supplied by the superior maxillary nerve. The lower lip and the inner surface of the cheek, the lower teeth and the gum, and the greater part of the tongue in front of the anterior pillars of the fauces, together with the mucous membrane of the alveolo-lingual sulcus, are supplied by the inferior maxillary nerve. The taste-fibres of the fore part of the tongue probably run in the chorda tympani; and the root of the tongue is supplied by the glosso-pharyngeal DISTRIBUTION OF CEREBRO-SPINAL NERVES. 339 nerve. The soft palate receives branches from the superior maxillary and glosso- pharyngeal nerves. The mucous membrane of the pharynx in its upper part, including the mouth of the Eustachian tube, receives twigs of the superior maxillary Fig. 220. — CUTANEOUS AREAS OP THE NERVES OF THE HEAD AND NECK. (Gr.D.T.) The areas supplied by the branches of the first division of the fifth are enclosed by black lines ; those supplied by the second division of the fifth and by branches of the cervical plexus by red lines : and those supplied by the third division of the fifth and by the posterior primary divisions of the cervical nerves by blue lines. S T, supratrochlear, I T, infratrochlear, and L, lachrymal branches of the first division of the fifth. The hinder part of the cheek, on which the word "auriculo " is placed, receives fibres of the auriculo-temporal nerve through the communication with the facial. The black spots denote the points at which the respective nerves become superficial. In this and similar figures the overlapping of adjacent nerves is indicated, so that along the boundary of each area there is a region which is supplied by the two nerves. It is, however, to be remarked that, owing to the difficulty of determining anatomically the precise extent of skin supplied by a branch of nerve, and the great degree of individual variability in this respect, neither the extent of the several areas nor the degree of overlapping are to be regarded otherwise than as approximate representations of what appears to be the average condition. 340 CEREBRO-SPINAL NERVES. C'«CUMFLEX •5-6 ..M E 0 I A N/ , \ Fig. 221. SENSORY DISTRIBUTION. 341 nerve ; in the rest of its extent it is supplied by the glosso-pharyngeal and pneumo- gastric nerves, mainly through the pharyngeal plexus, but in the neighbourhood of the superior aperture of the larynx it receives filaments of the superior laryngeal nerve. The larynx is supplied mostly by the superior laryngeal nerve, but in its lowest part it receives fibres from the inferior laryngeal, which also supplies the trachea. The sensory nerves of the (fsopliagus are probably derived from the pneumo-gastric. The mucous lining of the tympanic cavity and Eustachian tiibe are supplied by the glosso-pharyngeal nerve, while to the mastoid cells filaments pass from the same source, as well as from the inferior maxillary nerve (Luschka). The outer surface of the tympanic membrane, like the skin of the external auditory meatus generally, is supplied by the auriculo-temporal of the fifth and the auricular branch of the pneumo-gastric nerves. In the cranial cavity the dura mater receives branches from the three divisions of the fifth, the pneumo-gastric, and the hypoglossal nerves. 2. In the trunk. — The posterior divisions of the spinal nerves supply an area extending on the back from the vertex of the skull to the buttock. This area is narrow in the neck ; it is expanded in the upper dorsal region, extending over the back of the scapula; in the lower dorsal and lumbar regions its extent may be marked by a line drawn from the lower angle of the scapula (the arm hanging against the side) to the middle of the iliac crest ; and in the buttock its lower limit is indicated by a line from the tip of the coccyx to the great trochanter (see fig. 189, p. 282). The series of cutaneous branches is not continuous, there being gaps in the lower cervical and lower lumbar regions, corresponding to the middle parts of the brachial and lumbo-sacral plexuses ; that is, those spinal nerves which contribute most largely to the supply of the limbs do not furnish dorsal cutaneous offsets. The area supplied by the cervical plexus, besides extending upwards, as already mentioned, on the lateral part of the skull, stretches over the front and sides of the neck, and the upper part of the shoulder and breast. The area of the anterior divisions of the dorsal and first lumbar nerves meets superiorly with that of the cervical plexus, and posteriorly with that of the posterior divisions of the dorsal and lumbar nerves. It passes down over the haunch and along by the outer part of Poupart's ligament, and includes part of the penis and scrotum, and a small portion of the integument of the thigh internal to the saphenous opening. This extensive area may be subdivided by a line passing through the nipple downwards to the centre of Poupart's ligament into a mesial region supplied by the anterior cutaneous branches of the nerves, and a larger lateral region supplied by the lateral cutaneous branches. In the former region the skin over the ensiform process is supplied by the sixth and seventh dorsal nerves, and that around the umbilicus usually by the tenth dorsal nerve. The root of the penis on its dorsal aspect and a part of the scrotum anteriorly are Fig. 221. — CUTANEOUS AREAS OF THE NERVES OP THK UPPER LIMB. (Gr.D.T. ) A, anterior view ; B, posterior view. The areas supplied by the circumflex and musculo-spiral nerves, derived from the posterior cord of the brachial plexus, are circumscribed by red outlines ; those of the ulnar, internal cutaneous, and nerve of Wrisberg (W), from the inner cord of the plexus, together with the intercosto-humeral nerve, by blue lines ; and those of the mus3ulo-cutaneous from the outer cord of the plexus, with the median derived from both outer and inner cords, by interrupted black lines. The lower limit of the supra- clavicular nerves over the shoulder is also shown by a broken black line. The numerals following the names of the nerves indicate the spinal nerves from which the latter arise ; 3, 4, 5, 6, 7, 8, the corresponding cervical nerves ; 1, 2, the first and second dorsal nerves. The cutaneous branches of the musculo-spiral are distinguished as follows : — I, internal cutaneous ; II, upper, and III, lower external cutaneous. 342 CEREBRO-SPINAL NERVES. POST.\ POST. SACRAL"*! 2 / Fig. 222. -CUTANEOUS AREAS OF THE NERVES OF THE LOWER LIMB. ((r.D.T.) A, anterior view ; B, posterior view. For explanation, see opposite page. SENSORY DISTRIBUTION. 343 supplied by the ilio-inguinal and geni to-crural nerves (1 /). The greater part of the penis, the lower and hinder parts of the scrotum, and the perineum are supplied by the pudic nerve (2, 3, 4 s), the scrotum also receiving branches from the inferior pudendalof the small sciatic (2, 3 s). The branches to the penis are derived mainly from the second sacral nerve, to a less extent from the third ; those to the scrotum and fore part of the perineum chiefly from the third nerve, but in part also from the second ; and those to the hinder part of the perineum from the fourth and third sacral nerves (Paterson). 3. In the upper limb. — The shoulder, supplied superiorly by the descending branches of the cervical plexus (3, 4 c), receives its cutaneous nerves inferiorly from the circumflex nerve (5, 6 c). The arm internally is supplied by the intercosto-humeral nerve (2 d) and the nerve of Wrisberg (1 d). The inner and anterior part is supplied by the Fig. 223. — NERVE-SUPPLY OP THE SKIN OP THE SOLE. (Gr.D.T.) The areas enclosed by red lines are those supplied by the external cutaneous nerve, the middle and internal cutaneotis, and the internal saphenous branches of the anterior crural nerve, the perforating cutaneous nerve, and the lateral cutaneous, rnusculo-cutaneous, and anterior tibial branches of the peroneal nerve, i.e., the dorsal offsets of the limb-plexus. Those enclosed in blue lines are supplied by branches derived from the ventral offsets of the limb-plexus, viz., the calcaneo-plantar branch of the posterior tibial and the plantar nerves. The area of the small sciatic is enclosed internally by a blue and externally by a red line, corresponding to the double nature of the nerve (see p. 325). The area of the inner side of the leg supplied by the obturator and internal cutaneous in common, and that supplied by the external saphenous, are enclosed in interrupted black lines, the nerves concerned being derived partly from dorsal and partly from ventral divisions. internal cutaneous nerve (8 c, 1 d} and the posterior and outer parts by the circum- flex (5, 6 c), and by the internal and external branches of the musculo-spiral nerve (6, 7, 8 c}. The forearm, anteriorly and on the outer side, is supplied by the musculo- cutaneous (5, G c) ; on its outer and posterior aspect by the lower external cutaneous branch of the musculo-spiral (6, 7, 8 c), and inferiorly by the radial branch (6, 7 c) of the same nerve. On the inner side, both in front and behind, is the internal cutaneous nerve (8 c, 1 d), and inferiorly are branches of the ulnar (8 c, 1 d). On the lack of the hand are the radial and ulnar nerves, the radial (6, 7 c) supplying about three fingers and a half or less, and the ulnar (8 c) one and a half or more. On the front of the hand, the median nerve (6, 7, 8 c, 1 d) supplies three fingers and a half, and the ulnar ( 1 d, or 8 c, Id) one and a half. In the palm is a branch of the median, and also a branch of the ulnar, given off above the wrist. On the thenar eminence are branches of the musculo-cutaneous, median, and radial nerves. 4. In the lower limb. — The buttock is supplied from above by the cutaneous branches of the posterior divisions of the lumbar nerves, with the ilio-hypogastric (17) 344 CEREBRO-SPINAL NERVES. and lateral branch of the last dorsal nerves ; internally by the posterior divisions of the sacral nerves ; externally by the posterior branch of the external cutaneous nerve (2, 3 7) proceeding from the front ; and inferiorly by the perforating cutaneous nerve (2, 3 s) and branches of the small sciatic nerve (1, 2, 3 s) proceeding from below. The thigh is supplied externally by the external cutaneous nerve (2, 3 7) from the lumbar plexus ; posteriorly, and in the upper half of its inner aspect, by the small sciatic (1, 2, 3 s) ; anteriorly, and in the lower half of the inner aspect, by the middle and internal cutaneous (2, 3 7) of the anterior crural, the latter being frequently assisted by the obturator nerve (2, 3, 4 I). The leg is supplied posteriorly by the small sciatic (1, 2, 3 s) and short saphenous (1, 2 s) nerves; internally by the long saphenous (3, 4 /) and branches of the internal cutaneous of the thigh (2, 3 7) (or obturator) ; and outside and in front by cutaneous branches of the external popliteal nerve (5 7, 1, 2 s) and by its musculo- cutaneous branch (4, 5 7, 1 s). On the dorsum of the foot are the branches of the musculo -cutaneous (4, 5 7, 1 s), supplying all the toes with the exception of the adjacent sides of the first and second, which are supplied by the anterior tibial (4, 5 7, 1 s), and the outer side of the little toe, which, with the outer margin of the foot, is supplied by the short saphenous nerve (1, 2 s). The long saphenous (3, 4 7) is the cutaneous nerve of the inner side of the foot. The sole of the foot is supplied in its posterior part, together with the inner side of the heel, by the calcaneo-plantar branch of the posterior tibial nerve (1, 2 s). In front of this, the inner and larger part is supplied by the internal plantar nerve (4, 5 7, 1 s), which extends ^to the inner three toes and a half, while the outer part, with the remaining one toe and a half, is supplied by the external plantar nerve (1, 2 s). Over the outer side of the heel, and along the outer margin of the sole, are branches of the external saphenous nerve (1, 2 s). CUTANEOUS DISTRIBUTION OF THE SPINAL NERVES TO THE TRUNK AND LIMBS. The manner in which the several spinal nerves are distributed to the skin has been greatly elucidated by the experimental investigations of Sherrington, the dissections of Herringham and Paterson, and the clinical and pathological observations of Koss, Thorburn, Head, and others. From these it would appear that in the trunk the branches of each dorsal (segmental) nerve are generally distributed to a continuous area of skin, which has the form of a zone extending horizontally or obliquely from the dorsal to the ventral median line (see fig. 225, A, B, C). According to the observations of Head, the upper dorsal nerves form exceptions to this statement, their zones being interrupted laterally by the interposition of the upper limb, into which the middle portions of the first and second nerves (corresponding to their lateral cutaneous offsets) are prolonged ; but Sherrington found in the monkey that there was complete continuity between the trunk and limb portions of the areas of these nerves. Inferiorly, the zone of the last dorsal nerve is produced downwards over the hip ; and the first lumbar nerve, which resembles a dorsal nerve in its distribution, also supplies a zone which is similarly extended laterally over the hip, as well as ventrally to the penis, scrotum, and upper part of the thigh ; while with the second lumbar nerve the series of limb-nerves proper commences. These zones, moreover, overlap to a considerable extent, owing partly to the communications established between the several trunks, as is especially the case with the lower intercostal nerves (see p. 310), and partly to the crossing of CUTANEOUS DISTRIBUTION OF SPINAL NERVES. 345 their terminal filaments, so that there is probably no spot of the skin which is supplied only by one spinal nerve (Sherrington). In the limbs, although the nerves have been mingled in the plexuses, there is a similar principle to be recognized in their ultimate distribution, the fibres derived from the several spinal nerves being supplied to definite continuous areas in positions which are readily explained by reference to the mode of development of the limb. Thus, the upper nerves are distributed along the preaxial side of the limb, and the lower nerves along the postaxial side, while the intermediate nerves descend along the centre of the limb, and supply only the more distal parts. The skin at the root of the limb is not supplied by offsets of the limb-plexus, but by branches of nerves which have been drawn out, as it were, with the skin of the adjoining part of the trunk during the development of the limb. dorsal or ventral, m&ckcttt tine, Head Fig. 224. --SCHEME OF THE SENSORY SPINAL SKIN-FIELDS OF THE HIND LIMB OF MONKEY (Macacus rhesus). (Sherrington.) 10, 11, 12, areas of lower dorsal nerves ; 1 — 7, areas of lumbar nerves ; 8 — 11, areas of sacral and caudal nerves. Of the seven lumbar nerves in this monkey, the second and seventh correspond respectively to the first lumbar and first sacral nerves of man. The overlapping of the skin-fields is not indicated. The arrangement is the same on the dorsal and ventral aspects. Ths following rules have accordingly been formulated by Herringham from his observations on the nerves of the upper limb, and have been confirmed by Paterson for the lower limb : — A. Of two spots on the skin, that -which is nearer the preaxial border tends to be supplied by the higher nerve. B. Of two spots in the preaxial area, Ihe lower tends to be supplied by the loiver Fig. 225. — SEGMENTAL CUTANEOUS AREAS FROM THE FIRST DORSAL TO THE FOURTH SACRAL, AS DETERMINED BY CLINICAL AND PATHOLOGICAL OBSERVATIONS IN MAN. (Head.) On the right side of the figures the areas are marked by different colours and modes of shading; on the leftside the " maximum spots " (seat of most marked tenderness and pain) of the areas are shown. The several dorsal, lumbar and sacral areas are indicated each by the initial letter followed by a number. In C, C 7 is the seventh cervical spine, 3 to 12 are the corresponding dorsal spines, and L 1 to 4 are lumbar spines. THE SPINAL NERVES. •D.L Fig. 225. CUTANEOUS DISTRIBUTION TO TRUNK AND LIMBS. 347 Fig. 225. 348 THE SPINAL NERVES. nerve, and of two spots in the postaxial area, ilw lower tends to be supplied by the hu nerve. CervS. CutM Fig. 226. — THE SEGMENTAL CUTANEOUS AREAS FROM THE THIRD CERVICAL TO THE FIRST DORSAL. (Head.) la the upper limb, as is shown in fig. 221, the shoulder is supplied by offsets of the cervical plexus, proceeding from the third and fourth cervical nerves; the preaxial side of the limb, extending from the outer side of the shoulder to the CUTANEOUS DISTRIBUTION TO TRUNK AND LIMBS. 349 thumb, is supplied by the fifth and sixth cervical nerves ; and the postaxial side, from the little finger to the axilla, by the eighth cervical and first and second dorsal nerves. The seventh cervical nerve does not become superficial on the ventral aspect until the hand is reached, although on the dorsal aspect it appears earlier in the lower external cutaneous branch of the musculo-spiral, but here it is probably distributed to the lower part of the area of that nerve. The digits are supplied by the sixth, seventh, and eighth cervical, and first dorsal nerves, in this order, from the radial (preaxial) to the ulnar (postaxial) side. In the lower limb (figs. 222 and 223) the skin of the hip receives its nerves from the lateral cutaneous offsets of the last dorsal and first lumbar nerves, and from the posterior primary divisions of the lumbar and sacral nerves, while the anterior division of the first lumbar nerve reaches the upper part of the thigh in front. The nerves of the preaxial and postaxial borders of the limb are not so readily traced as in the case of the upper limb, owing to the displacement which has taken place with the marked rotation of the lower limb during development, and the great extension L.R LM Fig. 227. — THE SEGMENTAL CUTANEOUS AREAS FROM THE SECOND TO THK FIFTH LUMBAR. (Head.) The second lumbar ai*ea is marked in cross lines, the third in vertical lines, the fourth with circles, and the fifth with dots. of the area supplied by dorsal branches of the limb-nerves, with a corresponding reduction of the ventral area. The preaxial border may be represented by a line following the course of the internal saphenous vein from the groin along the inner border of the sartorius to the knee, and thence along the inner border of the tibia to the ankle and inner border of the foot ; and the postaxial border by a line running from the coccyx along the lower border of the gluteus maximus, thence down the postero-lateral aspect of the thigh to the back of the head of the fibula, and descend- ing along the leg over the external malleolus to the outer border of the foot (Paterson). Along the preaxial border, as thus defined, are the second, third, and fourth lumbar nerves, while along the postaxial border are found the first, second, and third sacral. It will be observed that both of the lines are overstepped to some extent by nerves of dorsal origin, and that the area supplied by ventral nerves is reduced to a strip along the postero-internal part of the thigh, over but not completely covering the hamstring and adductor muscles, and along the back of the leg, but spreading out VOL. III., PT. 2. Z <'KIM<;i',i;o-snN \l, \h.i;VKS. in thi- fool, to the whole hivudtli of the solo. The lil'lh luml>;ir uer\e docs no! hceome etilaneoiis on I he vein ral aspect mil d the sole is reached, hut in I he dorsal nerves it, appears earlier in the lateral cutaneous hraneh ofilie peroneal. 'The toes are supplied l>y the fourth and lil'lh luinhar, and I he first, and second sacral nerves, in this order, from the preaxiul to the postaxial side. The disposition ..I' (he cutaneous arras of I lie segment a 1 nerves in the Innli. as determined 1»V Sherriii» I on for I lie pelvic liniti ot' I lie monkey, is shown dia:1 ramniat iea 1 1 v in tiy.'J'JI. The .e\ era I tie Ids are seen to lie arranged in^ regular order a Ion L; a line continued out wards from the dorsal or vent ral median line of I lie t rim k, over t he correspond iny surface of I he limb, and form- ing a kind of secondary axial line for the latter. The lields of I he preaxial nerves eoiist.il n I e i de ccndm:' series almi" this line, the sixth Inmhar field spreads from the end of the axial line to the extremity of the limit, and the lields of the postaxial nerves, less numerous than the preavial, form an ascending series. The arranycment of the cutaneous nerves does not a",ree with thai of the mol or ner\ es of I he limh, \\hich supply each a coiititrnoiis band rn nn i n L; pa ral lei lo i he limit-axis from the I rnnk to I he free Itorder of I he limit. The in use I es of a given part of the limb and the overlying integument are, therefore, not necessarily supplied l>v t he same se^ineutal nerves ( SherriuL;'tou ). I 'i". tires L'l'.'i. 'J'Ji'i ami !"_' 7 represent, (he •• se-.- mental areas" of tlu> skin oxer the trunk and limits as determined hy Head from clinical observations. These areas are. however, not the re;/ ions supplied by the respective posterior spinal nerve roots, but represent rat her the parts of the skin in connection with the segments of the j^rey matter of the spinal eord by means ,if lib res subserving the sensations of pain, heat, and cold, but not. touch. They differ --I rikin;1,! \ from the areas of the posterior nerve roots in not overlapping, except to a small extenl in (he neck and upper limbs, whereas I he root areas overlap so much that there is no loss of tactile sensation after division til a single posterior root. ( Sherrinv.ton, Head). II ma\ also be pointed out thai the areas as designated by Head do not always ai;rec with the distri- bution of I he corresponding ner\e- as determined anatomically. Thus, the area marked 1> .'i on the inner side of the arm corresponds rather to I he brachial (list rilmt i< -n of t he second dorsal iierxe through its mlcrcosto- humeral branch and the communication with the nerve ol \\rishep.'.. while the third dorsal nerye does not usually contribute largely to the supply of the arm. Similarlv, I he areas marked I) II. I) !'_', and I/ I, would seem on anatomical ;• rounds, :>s well as from observations in cases of injury, as shown by Thorburu. to correspond more nearly to the twelfth dorsal and first and second lumbar nerves, it is therefore possible thai. while the !',d ici a I a rran " • •men I anil distribution of the sey.'inental areas, as well as their visceral associations, have been in principle correct ly IVCOL: n i /ed by Head, some modifications in the details of limitation and enumeration of these areas mav be rendered necessary by more extended ohservat ions. SENSORY DISTRIBUTION OP THE SPINAL NERVES TO THE VISCERA. There is strong reason for believing thai the tlioracie and abdominal viscera are supplied \\ith sensory t-hres derived from the spinal nerves, and passing through the sympathetic. In IliedoLT Kd;;vwort h has traced mednllatcd fibres of medium si/.e. which he regards as sensory. Irotii the posterior roots of the spinal nerves into the s\ mpat het ic. and thence to the several viscera : and his results are ^cncralh in close agreement with the inferences drawn from clinical observations in man (Head), although their accuracy in some particulars is disputed by l,ani;-ley. Kolliker also recoL>;ni/,cs mednllatcd sensory nerve libres passing without interruption from the posterior roots of spinal nerves through the sympathetic to the viscera. Indirect evidence as to the source of these fibres is furnished by the seat of "referred pain' in alVcctiotis ol the several organs. Arrordin:; to the hypothesis of Ross. the pain is referred in such cases to part s supplied hy somatic sensory libres having t heir origin t rom the nerves in which the sensory fibres of the a Heeled \iscusare contained, owiniv to dilVnsion of the irritation conveyed by the latter libres in the corresponding segment of the grey matter of the spinal cord. The following table, taken from Head, shows the probable origin of the sensory fibres of the different organs : — Heart.-l. •_'. :i dorsal. Lnnirs. 1. •_'. 3, I. I dot-sal. Stomach. ('•. 7. *. !> dorsal. Cardiac end from ('•. 7. 1'yloric end from !>. Intestines.— (n) Down to upper part of rectum, D. lo. n. 12 dorsal. (A) Rectum. •_'. ::. ! sacral. Liver and ( iall-l'daddcr. (\\ .'), 7, S, «». 10 dorsal. Kidney and Ureter.—10, 11, 12 dorsal. Upper part of ureter, 10 dorsal. At lower end ol ureter. 1 lumbar tends to appear. Bladder. — («) Mucous membrane and neck of bladder, (1), 2, 3, 4 sacral, (ft) Over- distension and inett'ectual contract ion. 11. 1 L' dorsal, and 1 lumbar. \n sci LAB DISTRIBUTION, 351 I'roslalr. 1(1. I I, ( 12) dor :i!. I, 2, .'{ sarral, : ml .. lumltar. Kpididyniis. II, I L' dorsal, and I lumbar T««Ht,is. 10 dorsal. Ovary. - 10 dorsal. App.'iidayvs, \c. II and I "2 dorsal, I lumkir. I'ti-rus. (11} In nmt rael.ion, |O. II, I'J dorsal, :uid I lumbar ( // ) O. ulrri, (I), 2, J{, -1 sacral ( .'. lnini.;if \ <-i \ rand y ). LITERATURE OP THE DISTRIBUTION OF SENSORY NERVES. Edtfeworth, p. H., (hi r«l ,SV //.w/-// Xij,/// <>f tin' Tln>,;i,-i,- m/, .Iniiin. of l'liys;.y., xiii, |,S!)± Head, H., (hi DithirbantW <>/' S< fixation, ///'/// r.,-/'"'""' /v/' '"' '"''' '" '/"' /'"'" "/ Vi /)in('«m; I'.rain, |.;irls Ixiaixl Ixii, I Mil.",, and Ixvii, IS'.t). Herrinsrham, W. P.. Tin- Mi, ml,- Aunt,,,,,,/ ,,/' //,, /Imr/u'nf /Vo-//x, I'ruc. Uoy. Soc,., di, 1H8C. LanR-ley, J. N., ^// I lie. /an/tr .M«lnll,ii«l Fibrcn »/'lli< ///Y//r Xi/xtiM, .lourn. ul 1'liyHgy., Mackenzie, J., HOIIK' I'uiiilx l>«irin, ii him-,1,,.. mnl Viwrul l>ini'iiii <>ftlie Nerves to tli< Lmi;,- /t/Hifi, Journ. of Anal., \xviii, I.S1KI I. Ross, J., On Ih, Myinritt,if DixtrilHitinii <>/' ^'imni-if />i'*<,rili-i:<<, liraiu, 1888, and in "ShidirH in \iial,iiniy,'1 t.lic Owens < !oll/nr/'.;// iliuliun ,,/' lli< I ''Hire* of t/ir Po^erior Root H nffiinw Spinal AV/w/i, I'n.r. Roy. Hoc., Hi, 1W2, and JMiil. Tran , ! Starr, M.Allen, Ann'ii'-m .lonrn Mi'd. Sci., May, I SHH ; Aora/ A inrnt/ifnin. nan nln <>f 1. 1: * '.an H of tin- L<,ir,r Xj,in' f I'nrtiini <>/' tin ,^/iiiin/ ('nr/f, I'.iain, part Ixvii, 1894. Thorburn, W., A ('<>„<,•;/,„/;<>„ in //,, ,S'///7/r/-i/ uf II,, ,S/, //,,// t',,rt/, IHH!»; 77/r AV//.VI/V/ />//,, 'in/inn nf ^n/i/ti/ \> n/Kit" .\<-nr«[• O/Hrjfdr/ic In 1 1 ten, SYNOPSIS OF THE MUSCULAR DISTRIBUTION OF THE CEREBRO- SPINAL NERVES. J . To muscles of the head and fore part of the neck. — The muscles ofthfi orbil arc mostly supplied by the third cranial nerve — the superior division of that nerve being distributed to the levator |)al|>(-br;i! and the HUpcrior IVC,|,IIK inuscleH, and the inferior division to the infi-rior :nid internal rec.ti and tlie inferior oblique. rrii(! Huperior oblique muscle is Huj)plied by the fourth nerve, and the external rectus by the sixth ; wliili UK- tensor tarsi has no special nerve apart from those of the orbieularin pidpebrarinn, wliicli :..n: derived IVoin the fjw.i;!.!. The Nii/t(r/iaa/. wmrlcs of I In- face, and scalp, which are associated in their action as a tfronp of muscles of expression, together with the buccinator muscle, are supplied by t he seventh cranial nerve, the retnihens auriculam and occipitalis muscles being supplied by its posterior auricular branch. The deep muscle of'thc f employed in mastication, vi/., Uie temporal, masseter, and two pterygoid muscles, are supplied by the inferior maxillary division of the fifth cranial nerve. M uncles above ike ////«•/>/ hone. — The mylo-hyoid muscle and anterior belly of the digastric are supplied by a branch of the inferior maxillary division of the fifth cranial nerve ; the posterior belly of the digastric muscle and the stylo-hyoid (together with the Htapcdius muscle) are supplied l,y br-.m-lieH of the facial. The muscles of the tongue receive their nervous supply from the hypoglossal nerve ; and the genio- hyoid muscle is supplied (like the infrahyoid muscles) by the upper cervical nerves. The mu8clct> ascmdiny to Ike kyoid bone and larynx, viz., the sterno-hyoid, omo- hyoiil, and sterno-thyro-hyoid, are supplied from the upper cervical nerves through their communications with the hypoglossal nerve and the ansa cervicalis. z 2 352 CEREBRO -SPINAL NERVES. The larynx, pharynx, and soft palate. — The crico-thyroid muscle is supplied by the external laryngeal branch of the pneumo-gastric nerve, and the other intrinsic muscles of the larynx by the recurrent laryngeal. The constrictors of the pharynx are supplied mainly by the bulbar part of the spinal accessory nerve through the pharyngeal branch of the vagus and the pharyngeal plexus ; and the levator palati, azygos uvulse, palato-pharyngeus, and palato-glossus are innervated from the same source. The stylo-pharyngeus, and possibly the middle constrictor in part, are supplied by the glosso-pharyngeal. The tensor palati is supplied through the otic ganglion by the inferior maxillary division of the fifth nerve (and the tensor tympaui is supplied in the same way). 2. To muscles belonging exclusively to the trunk, and muscles ascending to the skull. — All those muscles of the hack which act upon the spine and head, viz., the splenius, complexus, erector spinae, and the muscles more deeply placed, receive their supply from the posterior divisions of the spinal nerves. The sterno-mastoid is supplied by the spinal accessory nerve and a twig of the cervical plexus coming from the second cervical nerve. The rectus capitis anticus minor and rectus capitis lateralis are supplied by the first cervical nerve, the rectus capitis anticus major by the upper four cervical nerves ; the longus colli and seal-mi receive twigs from nearly all the cervical nerves. The muscles of the chest-ivall, viz., the intercostals, subcostals, levatores costarum, serrati postici, and triangularis sterni, are supplied by the intercostal nerves. The obliqui, transver sails, and rectus of the abdomen are supplied by the lower six to eight intercostal nerves ; and the internal oblique and transverse muscles also get branches from the first lumbar nerve. The cremaster muscle is supplied by the genital branch of the genito-crural nerve (1, 2 I). The quadratus lumhorum receives small branches from the last dorsal and upper one or two lumbar nerves. The diaphragm receives the phrenic nerves from the fourth and fifth cervical nerves, branches from the lower intercostal nerves, and likewise sympathetic filaments from the plexuses round the phrenic arteries. The muscles of the urethra and. penis are supplied by the pudic nerve (2, 3, 4 s), the levator and sphincter ani by the pudic and the fourth sacral nerves ; and the coccygeus muscle by the fourth and fifth sacral nerves. 3. To muscles attaching the upper limb to the trunk. — The trapezius and the cleido-mastoid receive the distribution of the spinal accessory nerve, and, in union with it, offsets from the cervical plexus. The latissimus dor si receives the long subscapular nerve (7, 8 c). The rhomhoidei are supplied by a branch from the fifth cervical nerve. The levator anguli scapulae is supplied by branches from the third and fourth cervical nerves, and partly also by the branch to the rhomboid muscles. The serratus magnus has a special nerve, the posterior thoracic, derived from the fifth, sixth, and usually the seventh cervical nerves. The subctavius receives a branch from the place of union of the fifth and sixth cervical nerves. The pectorales are supplied by the anterior thoracic branches of the brachial plexus, the larger muscle usually receiving fibres from the lower four cervical and first dorsal nerves, and the smaller from the last two cervical and first dorsal. 4. To muscles of the upper limb. — Muscles of the shoulder. — The supra- spinatus and infraspinatus are supplied by the suprascapular nerve (5, G c) ; the subscapularis by the upper and lower subscapular nerves (5, K c) : the teres major by the lower subscapular (5, 6 c) ; and the deltoid and teres minor by the circumflex nerve (5, 6 c). MUSCULAR DISTRIBUTION. 353 Posterior muscles of the arm and forearm. — The triceps (7, 8 f), anconeus (7, 8 f), supinator longus (6 c), and extensor carpi radialis longior ((>, 7 c) are supplied by direct branches of the musculo-spiral nerve ; while the extensor carpi radialis brevior (6, 7 c), the supinator brevis ((> c), and the other extensor muscles in the forearm (7 c) receive their branches from the posterior interosseous division of that nerve. Anterior muscles of the arm and forearm. — The coraco-brachialis is supplied by the seventh cervical nerve, and the biceps and brachialis anticus by the fifth and sixth cervical nerves through the musculo-cutaneous trunk ; the brachialis anticus likewise receives a twig frequently from the musculo-spiral nerve (6 c). The muscles of the front of the forearm are supplied by the median nerve, with the exception of the flexor carpi ulnaris and the inner half of the flexor profundus digitorum, which are supplied by the ulnar nerve. The offsets to the pronator tere. and flexor carpi radialis are derived from the sixth cervical nerve, those to the flexor sublimis digitorum from the seventh and eighth cervical and first dorsal nerves, and those to the flexor carpi ulnaris, flexor longus pollicis, flexor profundus digitorum and pronator quadratus from the eighth cervical and first dorsal nerves. Muscles of the hand. — The abductor, opponens, and outer head of the flexor brevis pollicis are supplied by a branch of the median nerve (6, or 6 and 7 c). The lumbricales (7, 8 c, 1 d) receive their branches, the outer two from the median, and the inner two from the ulnar nerve. All the other muscles are innervated through the ulnar from the eighth cervical nerve. 5. To muscles of the lower limb. — Muscles of the hip. — The ilio-psoas is supplied by the second and third lumbar nerves, the branches to the iliacus being given off from the anterior crural. The gluteus medius and minimus and the tensor vaginae femoris are innervated by the superior gluteal (4, 5 I, 1 s), and the gluteus maximus by the inferior gluteal (5 I, 1, 2 s). The pyriformis (1, 2 s), quadratus femoris and inferior gemellus (4, 5 /, 1 s), and obturator internus with the superior gemellus (5 /, 1, 2 s), receive special branches from the sacral plexus. The obturator externus is supplied by the obturator nerve (3, 4 I). Muscles of the thigh. — The sartorius (2, 3 Z), pectineus (2, 3 /), and quadriceps extensor cruris (3, 4 I) are supplied by the anterior crural nerve. The adductor longus (2, 3 D, gracilis (2, 3, 4 /), adductor brevis (2, 3, 4 /), and adductor magnus (3, 4 I) are supplied by the obturator nerve, but the adductor magnus likewise receives a branch (4, 5 I) from the internal popliteal division of the great sciatic nerve. The hamstring muscles are supplied by branches of the great sciatic nerve, the semimembranosus (4, 5 /, 1 s), semitendinosus (5 I, 1, 2 s\ and long head of the biceps (1, 2, 3 s), receiving their branches from its internal popliteal division, and the short head of the biceps (5 /, 1, 2 s) from its external popliteal division. Anterior muscles of the leg and foot. — The muscles in front of the leg, together with the extensor brevis digitorum, are supplied by the anterior tibial nerve (4, 5 ?, 1 s). The peroneus longus and Irevis are supplied by the musculo-cutaneous nerve (4, 5 Z, 1 s). Posterior muscles of the leg. — The gastrocnemius (1, 2 5), plantaris (4, 5 Z, 1 *), popliteus (4, 5 /, 1 s), and soleus (5 /, 1, 2 s) are supplied by the internal popliteal nerve, the last muscle receiving also a second branch (1, 2 s) from the posterior tibial nerve. The flexor longus digitorum (5 /, 1 s), tibialis posticus (5 /, 1 s), and flexor longus hallucis (5 /, 1, 2 s) derive their nerves from the posterior tibial. Plantar muscles. — The flexor brevis digitorum, the abductor and flexor brevis hallucis, and the innermost lumbricalis are supplied by the internal plantar nerve (5 ?, 1 s) ; all the others, including the flexor accessorius and interosseous muscles, are supplied by the external plantar nerve (1, 2s). 354 THE SPINAL NERVES. MUSCULAR DISTRIBUTION OF THE SPINAL NERVES. The statements made in the foregoing synopsis, and in the following lists of the muscles supplied by each spinal nerve, are based mainly upon dissections and pathological observations in man, but in part also upon physiological experiments in the monkey. Owing to the difficulties of these investigations, and the limited number of observations that have as yet been made, there is still some uncertainty as to the exact supply of some of the muscles of the limbs, where the nerves are mingled in plexuses before passing to their distribution, and especially as to the range of individual variations. In the case of the short trunk-muscles, which are derived from a single myomere, the nervous supply is single, coming from the nerve of that segment. In more extended muscles, which are formed by the fusion of portions of several segments, the nervous supply is correspondingly multiple, although there is at times a reduction in the number of nerves in comparison with the segments from which the muscle appears to have been derived, e.g., in the quadratus lumborum and complexus. In the limbs the segmental arrangement of the muscles and nerves is obscured ; but with regard to the general disposition it may be stated that most if not all of the muscles are supplied from more than one spinal nerve, and that the muscles on the preaxial side of the limb tend to be supplied by higher nerves than those on the postaxial side. From the lists it will be seen that muscles of different action are often supplied from the same nerve-roots. Terrier and Yeo concluded from their experiments in the monkey that the muscles called into action by the stimulation of a single nerve- root entering into the brachial or crural plexus form a group executing some definite co-ordinated movement of the limb, but Sherrington, in numerous observations on the same animal, failed to find evidence of such an association. Risien Russell, while supporting Ferrier and Yeo as to the co-ordination, also points out tha^ (in the dog) when antagonistic muscles are represented in the same nerve-roots, one group predominates in one root and the opposite group in another root. Similarly, in man, at least for the larger joints of the limbs, the muscles producing the chief movements in opposite directions are mainly represented at different levels. Thus, the abductors of the shoulder are innervated mainly by the fifth cervical root, and the adductors by the sixth and seventh ; the flexors of the elbow are supplied mainly through the fifth and sixth cervical nerves, and the extensors through the seventh and eighth ; the extensors of the wrist predominate in the seventh, and the flexors in the eighth cervical and first dorsal nerves. So also in the lower limb, the flexors of the hip are represented mainly in the second and third lumbar nerves, and the extensors in the fifth lumbar and first and second sacral ; the adductors in the third and fourth lumbar, and the abductors in the fifth lumbar and first sacral nerves ; the flexors of the knee in the fifth lumbar and first and second sacral nerves, and the extensors in the third and fourth lumbar. TABLE OP THE MUSCLES SUPPLIED BY THE SEVERAL SPINAL NERVES. NERVE. ANTERIOR DIVISION. POSTERIOR DIVISION. 1st cervical .-. Rectus lateralis, Rectus anticus minor and major, Rectiis posticus major and Grenio-hyoid, Inf rahyoid muscles. minor, Obliquus superior and inferior, Complexus. 2nd cervical . . Rectus anticus major, Longus colli, Sterno-cleido- Obliquus inferior, Com- mastoid, Grenio-hyoid, Infrahyoid muscles. plexus, Splenius, Tra- chelo-mastoid. MUSCULAR DISTRIBUTION. NERVE. ANTERIOR DIVISION. 3rd cervical . . Rectus anticus major, Longus colli, Infrahyoid muscles, Scalenus medius, Levator scapulae, (Sterno-cleido-mastoid),1 Trapezius, (Dia- phragm). 4th cervical . . Rectus anticus major, Longus colli, Scalenus medius (and anticus), Diaphragm, Levator scapulae, Trapezius. 5th cervical . . Longus colli, Scaleni, (Diaphragm) . Levator sca- pulae, Rhomboidei, Serratus magnus, Sub- clavius, Supraspinatus, Infraspinatus, Teres minor, Subscapularis, (Teres major), Deltoid, (Pectoralis major), Biceps, Brachialis anticus. (>th cervical . . Longus colli, Scaleni, (Subclavius), Serratus magnus, (Supraspinatus, Infraspinatus, Teres minor), Subscapularis, Teres major, Deltoid, Pectoralis major. Biceps, Brachialis anticus, Pronator teres, Flexor carpi radialis, Supi- nator longus and brevis, Extensores carpi radiales, Abductor, Opponens and Flexor brevis pollicis. 7th cervical . . Longus colli. Scalenus medius,(Serratus magnus), Pectoralis major and minor, Latissimus dorsi, (Teres major), Coraco-brachialis, Triceps brachii, Anconeus, Flexor sublimisdigitorum, (Flexor profundus digitorum, Flexor longus pollicis, Pronator quadratus), Extensores radiales, Extensors of digits, Extensor carpi ulnaris, (Abductor, Opponens and Flexor brevis pollicis). Sth cervical . . Longus colli, Pectoralis major and minor, Latissimus dorsi, Triceps brachii, Anconeus, Flexors of digits, Flexor carpi ulnaris, Pro- nator quadratus, Adductores pollicis, Inter- ossei, Abductor, Flexor brevis and Opponens minimi digiti. 1st dorsal . . . Pectoralis major and minor, Flexors of digits, Flexor carpi ulnaris, Pronator quadracus, Intercostales. Levator costae, Serratus pos- ticus superior. 2nd dorsal . . Intercostales, Levator costae, Serratus posticus superior, (Triangularis sterni). 3rd dorsal . . ) Intercostales, Levatores costarum, Serratus 4th dorsal . . \ posticus superior, Triangularis sterni. 5th dorsal . . ) Intercostales, Levatores costarum, Triangularis (5th dorsal . . ] stemi, Obliquus externus, Rectus abdo- minis. 7th dorsal . . ) Intercostales, Levatores costarum, Subcostales, Hth dorsal . . f Obliquus extern as, Obliquus internus, Transversalis abdominis, Rectus abdominis. J)th dorsal . . "i Intercostales, Levatores costarum, Subcostales, 10th dorsal . > Serratus posticus inferior. Obliquus externus, llth dorsal . } Obliquus internus, Transversalis abdominis, Rectus abdominis. 12th dorsal . . (Quadratus lumborum), Obliquus externus, Obliquus internus, Transversalis abdominis, Rectus abdominis, Pyramidalis. 1st lumbar . . Quadratus lumborum, (Obliquus internus, Transversalis abdominis), Cremaster. 2nd lumbar . . (Quadratus lumborum), Cremaster, Psoas magnus, (Psoas parvus), Iliacus, Pectineus, Adductor longus, Adductor brevis, Gracilis, Sartorius. POSTERIOR DIVISION. Complexus, Transverso- spinales, Splenius, Erec- tor spinae. Transverso-spinales, Erec • tor spinas. 1 Names enclosed in parentheses indicate that the muscles are not always supplied from the nerve- root in question. 356 MUSCULAR DISTRIBUTION OF SPINAL NERVES. NERVE. 3rd lumbar ANTERIOR DIVISION. POSTERIOR DIVISION. Multifidus spinse, Erector spinae. Psoas magnus, Iliacus, Pectineus, Adductor longus, Adductor brevis. Adductor magnus. Gracilis, Obturator externus, Sartorius, Quadriceps. 4th lumbar . . (Psoas magnus). Adductor brevis, Adductor magnus, G-racilis, Obturator externus, Quadriceps, Gluteus medius and minimus, Tensor vaginae femoris, (Gluteus maximus, | Obturator internus), Quadratus femoris, | Semimembranosus, (Deep muscles of back of \ leg), Muscles of front and outer side of leg, Extensor brevis digitorum. 5th lumbar . . (Quadriceps), Adductor magnus, Grluteus maximus, medius and minimus, Tensor vaginas femoris, (Pyriformis), Quadratus femoris, Obturator internus, Hamstrings, Muscles of leg (except gastrocnemius), Extensor brevis digitorum, Inner muscles of sole. 1st sacral . . . Gluteus maximus, medius and mini- \ mus, Tensor vagina3 femoris, Pyriformis, Obturator internus, Quadratus femoris, (Adductor magnus), Hamstrings, Muscles of leg and foot. 2nd sacral . . . Gluteus maximus, (Gluteus medius and minimus, Tensor vaginae femoris), Pyriformis, Obtu- ' rator internus, Semiteniinosus, Biceps, Multifidus spina?. (Muscles of front of leg, Peronei), Gastro- cnemius, Soleus, Flexor longus hallucis, (Flexor longus digitorum, Tibialis posticus), Outer muscles of sole, Perineal muscles. 3rd sacral . . . (Pyriformis), Biceps, long head, (Gastrocnemius. Soleus, Muscles of sole), (Levator ani, Coccygeus), Perineal muscles, •ith sacral . . . Levator ani, Coccygeus, Perineal muscles. 5th sacral . . . (Coccygeus). The unstriped muscles of the viscera and other parts are also under the influence of fibres derived from the cerebro-spinal nerves. These will be referred to in the description of the sympathetic. / LITERATURE OF THE MUSCULAR DISTRIBUTION OF SPINAL NERVES. Beevor, C. E., and Horsley, V., Note on some of the Motor Functions of certain Cranial Nerves, and of the three first Cervical Nerves, in the Monkey, Proc. Roy. Soc., 1888. Bolk, L., Beziehungen zicischen Skelet, Muskulatur und Ncrvcn der Extremitaten, dargeleyt am Beckengilrtel, an dessen Muskulatur, sowie am Plexus lumbo-sacralis, Morphol. Jahrb., xxi, 1894. Eisler, P., Der Plexus lumbosacralis des Menschen, 1892. Ferrier, D., and Yeo, GK F., The Functional Relations of the Motor Roots of the Brachial and Lumbo-sacral Plexuses, Proc. Roy. Soc., 1881. Forg-ue et Lanneg-race. Distribution des racines motrices dans les muscles des membres, and Distribution Kpeciale des racines motrices du plexus lombo-sacre, Comptes rendus, 1884. Growers, "W. R., Diseases of the Nervous System. Herring-ham, W. P., The Minute Anatomy of the Brachial Plexus, Proc. Roy. Soc., 1886. Paterson, A. M., The Origin and Distribution of the Nerves to the Lower Limb. Journ. of Anat., xxviii, 1893—4. Huge, GK, Zeugnisse fur die metamere Verkilrzung des Rumpfes bei Saugethieren. Der Musculus rectus thoraco-abdominalis der Primaten, Morphol. Jahrb., xix, 1892; Verschiebungcn in den Endgebieten der Nerven des Plexus lumbalis der Primaten, Morphol. Jahrb., xx, 1893 (Nerves to abdominal muscles). Russell, J. S. Risien. An Experimental Investigation of the Nerve-roots which enter into the Formation of the Brachial Plexus of the Dog, Phil. Trans., 1892. Sherring-ton, C. S., Notes on the Arrangement of some Motor Fibres in the Lumlo-sacral Plexus. Journ. of Physg., xiii, 1892. Simon, A., Ueber die Bcziehungen bestimmter Muskeln zu bestimmten Abschnittcn der grauen Substanz des Ruckenmarks, In. Diss., Strassburg, 1892. Starr, M. Allen, American Journal of the Medical Sciences, May, 1888. Thorburn, W. A Contribution to the Surgery of the Spinal Cord, 1889. THE SYMPATHETIC NERVES. 35? THE SYMPATHETIC NERVES. The nerves of the sympathetic system are distributed to the internal viscera, together with other glandular organs of the body, to the heart and blood-vessels. Fig. 228. — DIAGRAMMATIC OUTLINE OF THE SYMPATHETIC CORD OF ONE SIDE IN CONNECTION WITH THE SPINAL NERVES. (Allen Thomson. ) The full description of this figure will be found at p. 275. On the right side the following letters indicate parts of the sympathetic nerves, viz., — a, superior cerviccil ganglion, com- municating with the upper cervical spinal nerves, and continued below into the great sympathetic cord ; b, middle cervical gang- lion ; c, d, lower cervical ganglion united with the first dorsal ; df, eleventh dorsal ganglion ; from the sixth to the ninth dorsal ganglia the origins of the great splanchnic nerve are shown, and from the tenth that of the small splanchnic nerve ; /, first lumbar ganglion; ss, first sacral ganglion. In the whole extent of the sym- pathetic cord the twigs of union with the spinal nerves are shown. and to the unstriped muscles of the body generally. Some organs, however, receive nerves also from the cerebro-spinal system directly, as the lungs, the heart, and the upper and lower parts of the alimentary canal ; and those viscera which are not supplied directly in this way receive fibres derived originally from cerebro-spinal nerves through their sympathetic plexuses. This division of the nervous system consists of a somewhat complicated collection of ganglia, cords and plexuses, the parts of which may, for convenience, be classified in two groups, viz., the principal gangliated cords, and the great prevertebral plexuses, with the nerves proceeding from them. The ganglia of union with cranial nerves, viz., the ciliary, spheno-palatine, otic, and submaxillary ganglia, which agree in their connections and structure with the ganglia of the sympathetic system, have already been described in connection with the fifth nerve. The foundation of the sympathetic is constituted by medullated fibres, for the most part of very small size (2'fyi and less), which pass by means of the white rami communicantes from certain of the cerebro-spinal nerves, into the cords and ganglia of the sympathetic. Here some of the fibres terminate in arborisations around the cells of the ganglia of the great sympa- thetic cord (vertebral or lateral ganglia of Gaskell), while others, which frequently run for a variable distance either upwards or downwards in the cord, pass by the rami efferentes to the prevertebral plexuses, where they may end similarly in the ganglia of those plexuses (prevertebral or collateral gang lia, Gaskell), or they may be continued on to the secondary plexuses, to break up in the ganglia close to or in the organs supplied (terminal ganglia, Gaskell). Some of the medullated fibres also pass through the several plexuses to the viscera or other parts without being 358 THE SYMPATHEI1C NERVES. interrupted in any of the ganglia above mentioned. From the cells of the ganglia other fibres, in great part it' not entirely non-medullated, arise. These are the proper sympathetic fibres. They run partly in the grey rami communicantes to the spinal nerves, partly in the rami efferentes and the offsets of the collateral and terminal ganglia to their ultimate distribution. The great gangliated cords (trunci sympathies) are two in number, and each consists of a series of ganglia (ganglia trunci sympat/iici), united by short intervening cords, sometimes double. These gangliated cords are placed symmetri- cally, partly in front, and partly on the side, of the vertebral column, extending from the base of the skull to the coccyx. Superiorly they are connected with Fig. 229. — SCHEME OF THE SYMPATHETIC CORD AND ITS CONNECTION* WITH THE SPINAL NERVES. (Gr. D. T. ) Meclullated fibres passing into and through the sympathetic cord are represented by continuous lines, pale fibres arising from the sympathetic ganglia by dotted lines. plexuses which enter the cranial cavity, while interiorly they converge on the sacrum, and terminate in a loop on the coccyx. The several portions of the cords are dis- tinguished as cervical, dorsal or thoracic, lumbar, and sacral, and in each of these parts the ganglia are equal in number, or nearly so, to the vertebrae against which they lie, except in the neck, where there are only three. Connection of the gangliated cords with the cerebro-spinal system. — The ganglia are severally connected with the anterior primary divisions of the spinal nerves in their neighbourhood by short filaments called rami communicantes, which are of two kinds, white and grey, the former consisting mainly of medullated fibres, and the latter of pale fibres. In some cases these are separate branches ; in others they are united in one cord, which then consists of a white and a grey part. As a rule, the communicating branches join the ganglia of the sympathetic trunk, but sometimes they unite with the part of the cord connecting adjacent ganglia. White rami communicantes are composed, as stated above, mainly of very fine medullated fibres passing from the spinal nerves to the sympathetic cord. The fibres proceed from both roots of the spinal nerves, but to a greater extent from the anterior. It is probable that the fibres derived from the posterior roots are for the most part afferent, but it has been shown by v. Lenhossek and others in the chick that the posterior roots also contain fibres which spring from cells of the spinal cord, and are believed to enter the sympathetic (Kolliker). These fibres have, however, as yet not been observed in mammals, and Sherrington in the cat and monkey failed to find evidence of any fibres in the posterior roots arising from cells of the spinal cord. Some of the medullated fibres are continued over the ganglia of the cord to enter the efferent branches ; others end in the ganglia, often ascending or descending for a considerable distance in the cord to reach ganglia at a higher or lower level than that of the communicating branch by which they pass to the sympathetic. The individual fibres also which terminate in the cord are not necessarily confined to one ganglion. According to Langley and Anderson, a single fibre may send KAMI COMMUNICANTES. 359 branches to several (about four) ganglia. In this way the fibres contained in one communicating branch may have a wide distribution in the sympathetic. White rami communicantes are not furnished by all the spinal nerves. According to (laskell, by whose investigations the fundamental constitution of the sympathetic and its relations to the cerebro-spinal nerves were first made clear, they are found in the dog from the second dorsal to the second lumbar nerve inclusive ; but Langley has shown that in the dog and cat white rami communicantes are given off by the spinal nerves from the first dorsal to the fourth lumbar, and in the rabbit from the first dorsal to the fifth lumbar inclusive. In man it is most probable that they exist from the first dorsal to the first or second lumbar nerves, perhaps also the third in some cases. The visceral branches of the second, third, and fourth sacral nerves (pelvic splanchnic* of Gaskell) correspond to white rami communicantes, although they do not join the sympathetic cord, but pass directly to the prevertebral plexuses ; and in this group also are to be included the visceral branches of the spinal accessory, vagus, glosso-pharyngeal, and facial nerves (cervico-cranial rami viscerales, Gaskell), as well as the short root of the ciliary ganglion from the third nerve. The medullated fibres passing into the sympathetic system are classified by Kolliker as follows : — («•) Sensory fibres which, when derived from spinal nerves, run in the posterior roots. (&) Vaso- and viscero-constrictors, proceeding from certain cranial (IX, X, XI) and spinal nerves, mainly from the anterior roots of the latter, but possibly also from the posterior roots. These fibres all end in ganglia of the sympathetic, and their action is transmitted through pale fibres springing from the cells of the ganglia.1 (c) "Vaso- dilators and viscero-inhibitory nerves, given off from the above-mentioned cranial nerves, and the anterior roots of spinal nerves. They are continued as medullated fibres, not forming any connection with nerve-cells, to their respective organs. The existence of special trophic and secretory fibres in the sympathetic is as yet uncertain. Grey rami communicantes are found passing between the sympathetic cord and all the spinal nerves. Their pale fibres arise wholly from the nerve-cells of the ganglia of the sympathetic cord, and for the most part from the cells of the ganglion with which the branch is connected. Pale fibres arising from the cells of one ganglion, and running along the cord to leave by the grey ramus of the next ganglion, only occur exceptionally (Langley). On entering the anterior primary division of a spinal nerve, the fibres of the grey ramus are directed both peripherally and centrally. Of those passing centrally, some go off in the posterior primary division of the nerve, others enter the sheath of the nerve, the surrounding tissue in the inter vertebral foramen, and the dura mater, running up to the latter in the posterior root. In the whole of the anterior root, and in the intradural portion of the posterior root, there are no pale fibres (Gaskell). The fibres passing distally in the anterior and posterior primary divisions of the spinal nerves have been shown, by experiments on animals, to supply vaso-motor nerves to the arteries of the body-wall and limbs, pile-motor fibres to the muscles of the hairs, and secretory fibres to the sweat-glands. Intermixed with the pale fibres in the grey rami communicantes there are also a 1 To this group must also be added the pilo-motor nerves, which have been shown by Langley and Sherrington to have a similar arrangement, as well as probably the motor nerves of the sphincter muscle of the iris, which pass from the third nerve through the ciliary ganglion. The lastr however, present the peculiarity that the fibres of the short ciliary nerves arising from the cells of the ciliary ganglion are medullated. It may also be observed here that doubt is thrown by Langley upon the universal validity of the rule that fibres passing from the cerebro-spinal nerves to the sympathetic are medullated until they reach the ganglion in which they end, while the fibres arising from the ganglion-cells are always non-medullated. He thinks that spinal fibres sometimes lose their medulla some distance before reaching the cells amongst which they end, and on the other hand that fibres proceeding from sympathetic ganglion-cells may in some cases be medullated, like the short ciliary nerves. He also considers it probable that a given fibre in the sympathetic is interrupted by a nerve-cell in one ganglion only. 360 THE SYMPATHETIC NERVES. few medullated fibres of varying size, even in regions where distinct white rami do not exist (Langley). .From each grey ramus a filament is given off to join the recurrent branch of Fig. 230. — THE SUPERIOR CKK- VICAL GANGLION OF THK SYMPATHETIC, WITH I !'S BRANCHES AND CONNEC- TIONS. (Henle. ) 1, styloid process ; '2, uvula ; 3, great cornu of liyoid bone, pushing up tlie posterior wall of the pharynx ; 4, oesophagus ; 5, thyroid body ; Sp, stylo-pharyngcns in uscle. Cc, common carotid artery ' Ci, internal carotid ; Ge, ex- ternal carotid ; t su, superior thyroid ; 1, lingual ; m e, facial. IX, gl osso-pharyngeal nerve ; X, vagus ; XII, hypo- glossal ; c1, first cervical ; c'2, second cervical ; ph, pha- ryngeal branch of vagus ; I r s, superior laryngeal ; d h, de- scending cervical nerve ; G c s, superior cervical gang- lion of sympathetic ; c i, as- cending branch ; j, jugular branch ; c d s. superior cardiac the corresponding spinal nerve, which is distribu- ted in the interior of the spinal canal (p. 278). Other filaments pass over the bodies of the verte- bras, supplying the in- tercostal and lumbar arteries, the ligaments, and the bones. The portions of the sympathetic cord inter- vening between the ganglia are composed of a white and a grey part, the former, which is usually the larger, consisting of medul- lated fibres continued from the white rami communicantes, and the latter of pale fibres, which arise in the ganglia and run along the cord before entering the efferent branches. The rami etferentes are the branches proceeding from the gangliated cord to the prevertebral plexuses, and likewise composed of medullated fibres of spinal origin and pale fibres springing from the ganglia. CERVICAL PART OF CORD. 361 The great prevertebral plexuses comprise three large aggregations of nerves, or nerves and ganglia, situated in front of the spine, and occupying respectively the thorax, the abdomen, and the pelvis. They are single and median, and are named respectively the cardiac, the solar, and the hypogastric plexus. These plexuses receive branches from the cerebro-spinal nerves, as well as from both the gangliated cords above noticed, and they constitute centres from which the viscera are supplied with nerves. CERVICAL PART OF THE GANGLIATED CORD. In the neck, the gangliated cord is deeply placed behind the great cervical blood- vessels, being embedded in the fascia forming the back of the carotid sheath, and resting on the muscles which immediately cover the fore part of the vertebral column. It comprises three ganglia, the first of which is placed near the base of the skull, the second in the lower part of the neck, and the third close to the head of the first rib. UPPER CERVICAL GANGLION. This is the largest ganglion of the great sympathetic cord, 20 mm. or more long and 4 — 6 mm. wide. It is continued superiorly into an ascending branch, and tapers below into the connecting cord, so as to present usually a fusiform shape ; but there is considerable variety in this respect in diiferent cases, the ganglion being occasionally shorter and broader than usual, and sometimes constricted at intervals. Ib has the reddish-grey colour characteristic of the ganglia of the sympathetic system. It is placed on the rectus anticus major muscle opposite the second and third cervical vertebrae, lying behind the internal carotid artery, and to the inner side of the vagus nerve. Connection with spinal nerves. — At its outer side, the superior cervical ganglion is connected with the first four spinal nerves by means of slender cords, which belong to the group of grey rami communicantes. The branches to the third and fourth nerves often pierce the rectus anticus major muscle ; and they may be given off from the upper part of the cord, instead of directly from the ganglion. The circumstance of this ganglion being* connected with so many as four spinal nerves, together with its occasionally constricted appearance, is favourable to the view that it may be regarded as consisting of several ganglia which have coalesced. The superior cervical ganglion is considered by Gaskell to be a distal or collateral ganglion It receives its cerebro-spinal fibres, which constitute the cervical splanchnic* of Gaskell. from the upper dorsal nerves, through the cervical part of the sympathetic cord. Connection with cranial nerves. — Small twigs connect the ganglion or its cranial cord with the lower ganglion of the pneumo-gastric, and with the twelfth cranial nerve, near the base of the skull ; and another branch (n. jugularis], which is directed upwards from the ganglion, divides at the base of the skull into two filaments, one of which ends in the petrosal ganglion of the glosso-pharyngeal nerve ; while the other, entering the jugular foramen, joins the ganglion of the root of the pneumo-gastric. From the lower part of the ganglion a filament sometimes runs forwards and downwards to join the external laryngeal nerve. This branch is described as normal by many anatomists, but according to Drobnik it is only exceptionally present. Besides the branches connecting it with cranial and spinal nerves, the first cervical ganglion gives off also the ascending branch, pharyngeal branches, the upper cardiac nerve, and branches to blood-vessels, as well as two or three filaments which pierce the prevertebral muscles to supply the upper cervical vertebra? and their ligaments. THE SYMPATHETIC NERVES. 1. ASCENDING BRANCH AND CRANIAL PLEXUSES. — The ascending or carotid branch of the first cervical ganglion (n. caroticus internus) is soft in texture and of a reddish-grey tint, seeming to be in some degree a prolongation of the ganglion itself. In its course to the skull, it is concealed by the internal carotid artery, with which it enters the carotid canal in the temporal bone, and it is then divided into two parts, which are placed one on the outer, the other on the inner side of the vessel. The external division distributes filaments to the internal carotid artery, receives one or two carotico-tympanic twigs from the tympanic branch of the glosso- pharyngeal (p. 2 GO), and, after communicating by means of other filaments with the internal division of the cord, forms the carotid plexus. The internal division, rather the smaller of the two, supplies filaments to the carotid artery, and goes to form the cavernous plexus. The terminal parts of these divisions of the cranial cord are prolonged on the trunk of the internal carotid, and extend to the cerebral and ophthalmic arteries, around which they form secondary plexuses, those on the cerebral arteries ascending to the pia mater. One minute plexus enters the eye-ball with the central artery of the retina. Fig. 231. — CONNECTIONS OK THE SYMPATHETIC NKRVK THROUGH ITS CAROTID BRANCH WITH SOME OK THE CRANIAL NERVES. (From Sappey, after Hirschfeld and Leveille.) The full description of this ligure will be found at p. 240. The following numbers refer to sympathetic nerves and their connections : 6, spheno-palatine ganglion ; 7, Yidian nerve : 9, large deep petrosal nerve ; 10, a part of the sixth nerve receiving twigs from the carotid plexus of the sympathetic ; 11, superior cervical sympathetic ganglion : 12, its prolongation 15, tympanic nerve ; 16, t\vig uniting it to the sympathetic. in the carotid branch Carotid plexus. — The carotid plexus (plexus caroticus inlernus), situated on the outer side of the internal carotid artery at its second bend (reckoning from below), or between the second and third bends, joins the fifth and sixth cranial nerves, and gives many filaments to the vessel on which it lies. Branches. — (a) The connection with the sixth nerve is established by means of one or two filaments of considerable size, which are supplied to that nerve where it lies by the side of the internal carotid artery. (V) The filaments connected with the Gasserian ganglion of the fifth nerve proceed generally from the carotid plexus, but sometimes from the cavernous. (c) The large deep petrosal nerve passes forwards from the outer side of the artery to the posterior aperture of the Vidian canal, where it joins the large superficial petrosal from the facial to form the Vidian nerve, which is continued to the spheno- palatine ganglion (p. 243). (d) The small deep petrosal nerve passes between the carotid plexus and the tympanic plexus (p. 200). Cavernous plexus. — The cavernous plexus, named from its position in the sinus of the same name, is placed below and rather to the inner side of the highest turn of the internal carotid artery. Besides giving branches on the artery, it BRANCHES OF UPPER CERVICAL GANGLION. 3G3 communicates with the third, the fourth, and the ophthalmic division of the fifth cranial nerves. BRANCHES. — (a) The filament which joins the third nerve comes into connection with it close to the point of division of that nerve. (&) The branch to the fourth nerve, which may be derived from either the cavernous or the carotid plexus, joins the nerve where it lies in the wall of the cavernous sinus. (c) The filaments connected with the ophthalmic trunk of the fifth nerve are supplied to its inner surface. (d) The sympathetic root of the ciliary ganglion passes from the cavernous plexus into the orbit, either separately, or in connection with the nasal nerve, or, according- to Reichart, with the third nerve (p. 238). (e) Minute filaments are furnished to the pituitary body. 2. PHARYNGEAL NERVES AND PLEXUS. — These nerves arise from the fore part of the ganglion, and are directed obliquely inwards to the side of the pharynx. Opposite the middle constrictor muscle they unite with branches of the pneumo- gastric and glosso-pharyngeal nerves ; and by their union with these nerves the pharyngeal plexus is formed. Branches emanating from the plexus are distributed to the muscles and mucous membrane of the pharynx (p. 265). One or two filaments pass from these branches to the superior and external laryngeal nerves (fig. 228). 3. UPPER CARDIAC NERVE. — Each of the cervical ganglia of the sympathetic usually furnishes a cardiac branch, the three being named respectively the upper, middle, and lower cardiac nerves. These branches are continued singly, or in connection, to the large prevertebral centre (cardiac plexus) of the thorax. Their size varies considerably, and where one branch is smaller than common, another will be found to be increased in size, as if to compensate for the defect. There are some differences in the disposition of the nerves of the right and left sides. The upper or superficial cardiac nerve of the right side proceeds generally from two or more branches of the ganglion, with, in some instances, an offset from the cord connecting the first two ganglia. In its course down the neck the nerve lies in the back of the carotid sheath, along the front of the longus colli muscle ; it crosses either in front of or, less frequently, behind the inferior thyroid artery, and is placed in front of the recurrent laryngeal nerve. Entering the thorax, it passes in some cases before, in others behind, the subclavian artery, and is directed along the innominate artery to the back part of the arch of the aorta, where it ends in the deep cardiac plexus, a few small filaments continuing also to the front of the great vessel. Some branches accompany the inferior thyroid artery to be distributed to the thyroid body. In its course downwards this cardiac nerve is repeatedly connected with other branches of the sympathetic, and with the pneumo-gastric nerve. Thus, about the middle of the neck it is joined by one or more filaments from the external laryngeal nerve ; and, rather lower down, by one or two filaments from the trunk of the pneumo-gastric nerve (upper cervical cardiac branches) ; lastly, on entering the chest, it joins with the recurrent laryngeal. The upper cardiac nerve of the left side has, while in the neck, the same course and relations as that of the right side. Within the chest it follows the left carotid artery to the arch of the aorta, and usually crosses over that vessel to enter the superficial cardiac plexus. In some cases, however, this nerve ends, either wholly or in part, in the deep cardiac plexus, and it then descends behind the arch of the aorta. THE SYMPATHETIC NERVES, Varieties. — The cardiac nerves vary greatly in their disposition, and in many cases it is difficult, if not impossible, to recognize the arrangement which is described as typical. The superior cardiac nerve of the right side, instead of passing to the thorax in the manner stated above, may join the cardiac branch furnished from one of the other cervical ganglia. This nerve is sometimes wanting, especially on the right side ; in such cases it appears to be Fig. 232. — CONNECTIONS OP THE CERVICAL AND UPPER THORACIC SYMPATHETIC GANGLIA AM> XKRVES ON THE LEFT SIDE. (From Sappey, after Hirschfeld and Leveille.) The full description of this figure will be found at p. 263. The following numbers refer to the sympathetic ganglia and nerves, and those immediately connected with them ; 5, pharyngeal plexus ; 12, 13, posterior pulmonary plexus ; and to the reader's left, above the pulmonary artery, the superficial cardiac plexus ; 24, superior cervical ganglion of the sympathetic ; 25, middle cervical ganglion ; 26, conjoined inferior cervical and first thoracic ganglia ; 27, 28, 29, 30, second, third, fourth, and fifth thoracic ganglia. replaced by a larger superior cardiac offset from the vagus or its external laryiigeal branch (M. Alpiger). Drobnik describes a special yrctraclieal Iranc7i which is given off from the communication between the superior cardiac nerve and the recurrent laryngeal ; it descends on the trachea, and terminates partly in the pericardium, partly in the anterior pulmonary plexus. 4. BRANCHES TO BLOOD-VESSELS. — The nerves which ramify on the arteries (nn. carotid externi] spring from the front of the ganglion, and twine round the trunk of the external carotid artery (plexus caroticus externus). They are also prolonged on the branches of the artery, forming upon them slender plexuses which are named like the arteries they accompany. From the plexus on the facial artery MIDDLE AND LOWER CERVICAL GANGLIA. 365 is derived the filament which forms the sympathetic root of the subinaxillaiy ganglion ; and from that on the middle meningeal artery twigs are described as extend- ing to the otic ganglion, as well as to the geniculate ganglion of the facial nerve (external superficial petrosal nerve, p. 253). One filament descends from these nerves to the carotid gland. Microscopic ganglia are frequently met with in the vascular plexuses, and several larger ones of more constant occurrence have been described. The most important of these is the tciu/)or<* .s-///;/r ///<.*). It is described as formed by offsets from the cardiac nerves, and from the lower cervical as well as some of the upper thoracic ganglia. The small splanchnic nerve springs from the ninth and tenth (sometimes the tenth and eleventh) thoracic ganglia, or from the neighbouring part of the cord. It passes along with the preceding nerve, or separately, through the diaphragm, and ends in the lower part of the semilunar (or aortico-renal) ganglion. In the chest, this nerve often communicates with the great splanchnic nerve ; and in some instances it furnishes a branch to the renal plexus, especially if the lowest splanclinic nerve is very small or wanting. The smallest splanchnic nerve (nervus renalis posterior, Walter) arises from the last thoracic ganglion, and communicates sometimes with the nerve last described. After passing the diaphragm with the cord of the sympathetic, it ends in the renal plexus. Its place is frequently supplied by a branch of the small splanchnic nerve. CONSTITUTION OP THE THORACIC PART OP THE SYMPATHETIC. The thoracic portion of the gangliated cord receives most of the spinal fibres entering the sympathetic system (/;/'. p. 359). Only a small part of these end in the thoracic ganglia ; the greater number pass either upwards into the neck or downwards into the abdomen. The fibres ascending to the neck arise from the upper dorsal nerves ; they include the pupillo-dilator fibres, secretory fibres of the submaxillary gland, vaso-motor fibres of the head and neck, accelerator fibres of the heart, and others, all of which have been referred to in connection with the cervical sympathetic (p. 366). In addition to these, the following groups have been demonstrated experimentally in the lower animals : — («) Vaso-constrictor fibres of the pulmonary vessels have been shown by Bradford and Dean, in the dog, to pass out of the spinal cord by the thoracic nerves from the second to the seventh (mainly, however, through the third, fourth, and fifth nerves), and to end in the ganglion stellatum. (b~) Vaso-constrictor fibres of the limbs are connected with the vertebral ganglia. Those of the fore limb are given off by the dorsal nerves, in the dog from the third to the eleventh (Bayliss and Bradford), in the cat from the fourth to the ninth (Langley). Those of the hind limb are furnished, according to the same investigators, in the dog by the last three (11, 12, 13) dorsal and first three lumbar nerves, and in the cat by the last two or three dorsal and the first three or four lumbar nerves. (r) Secretory fibres to the sweat-glands of the fore foot leave the dorsal nerves from the third or fourth to the ninth, and pass to the ganglion stellatum ; while those of the hind limb emerge by the last two dorsal and upper three lumbar nerves, and descend in the cord to the lower lumbar and upper sacral ganglia— in the cat (Langley). (d) Pilo-motor fibres in the cat pass from the lower nine or ten dorsal nerves, as well as the upper three or four lumbar, to the vertebral ganglia (Langley). The splanchnic nerves contain : — (e) Viscero-inhibitory fibres of the stomach and intestine.— According to Langley and Dickinson they end in the ganglia of the solar plexus. (/) Vaso-motor nerves of the abdominal blood-vessels. — The existence of vaso-con- strictor fibres for the arteries of the alimentary canal in the splanchnic nerves is well established ; and, according to Langley and Dickinson, these nerves also contain the vaso- dilator fibres of the same vessels : both sets of fibres end in the ganglia of the solar plexus. Vaso-constrictor fibres of the portal vein and its tributaries were originally demonstrated by Mall ; according to Bayliss and Starling, in the dog, they are given off by the dorsal nerves from the third to the eleventh, but mainly from the fifth to the ninth. The nerves of the renal blood-vessels, both constrictor and dilator, are derived in the dog from the dorsal nerves from the sixth downwards, as well as (constrictors only) from the upper two lumbar nerves 370 THE SYMPATHETIC NERVES. (Bradford) : the renal vaso-motor fibres probably end in the ganglia of the renal plexus (Langley and Dickinson). () Motor fibres to the bladder, passing by the aortic plexus to the inferior mesenteric ganglion, and thence through the hypogastric and pelvic plexuses, to supply the circular muscle, including the sphincter. Associated with these there are probably inhibitory fibres of the longitudinal muscle. (tf) Motor fibres to the uterus, taking a similar course to the foregoing. (Motor fibres to the vas deferens in the male, or to the round ligament of the uterus in the female, were found by Sherrington in the monkey leaving the cord by the anterior roots of the second and third lumbar nerves (corresponding to the first and second lumbar of man),, and passing to their destination through the genital branch of the genito-crural nerve.) SACRAL PART OF THE GANGLIATED CORD. Over the sacrum, the gangliated cord of the sympathetic nerve is much diminished in size, and gives but few branches to the viscera. Its position on the front of the sacrum is along the inner side of the anterior sacral foramina ; and like the two SACEAL PART OF CORD. 371 series of those foramina, the right and left cords approach one another in their progress downwards. The upper end of each is united to the last lumbar ganglion by a single or a double intergauglionic cord ; and at the lower end they are connected by means of a loop, in which a single median ganglion, ganglion impar or coccygeal ganglion, placed on the fore part of the coccyx, is often found. The sacral ganglia are usually four in number ; but the variation both in size and number is more marked in these than in the thoracic or lumbar ganglia. Variety. — In one instance the cord was found terminating at the second sacral nerve (E. Fawcett, Journ. Anat., xxix, 329). Connection with spinal nerves. — From the proximity of the sacral ganglia to the spinal nerves at their emergence from the foramina, the communicating Fig. 235. — SACRAL PORTION OF THE SYMPATHETIC CORDS OP AN INFANT, SLIGHTLY ENLARGED. (Rauber.) s 1 — s 4, sacral ganglia ; c, coccygeal ganglion, showing indications of its origin by the fusion of two ganglia, and sending downwards branches which run with the middle sacral artery ; ri, interfunicular branches uniting the ganglia of the two sides ; below these is seen a small interfunicular ganglion. branches are very short : there are often two for one ganglion, and these are in some cases connected with different sacral nerves. The coccygeal nerve communi- cates with the last sacral, or the coccygeal ganglion. BRANCHES. — The branches proceeding from the sacral ganglia are much smaller than those from other ganglia of the cord. They are for the most part expended on the front of the sacrum, and join the corre- sponding branches from the opposite side. Some filaments from one or two of the upper ganglia enter the pelvic plexus, while others go to form a plexus on the middle sacral artery. From the loop con- necting the two cords, filaments are given to the coccyx and to the ligaments about it, and to the coccygeal gland. CONSTITUTION OF THE SACRAL SYMPATHETIC. There are no spinal fibres passing from the sacral nerves to the sympathetic cord, but the latter contains medullated fibres which descend from the lumbar region and terminate in the sacral ganglia. These fibres include vaso-constrictor and secretory fibres of the hind limb, and the pilo-motor fibres of the hindmost part of the body and the tail in the cat (Langley). The visceral branches of the sacral nerves (pclriv xplanchnics, Graskell) are equivalent to white rami communicantes (p. 359), but they pass directly into the pelvic plexuses, where a few of the fibres may turn upwards to the inferior mesenteric ganglion,1 while the larger number enter the plexuses of the pelvic viscera. They comprise : — (Y/) Motor fibres to the longitudinal muscle, and inhibitory fibres to the circular muscle of the rectum. 1 Fibres ascending to the inferior mesenteric ganglion are described by Graskell in the dog, but they were not found by Langley in the cat. 372 THE SYMPATHETIC NERVES. (I) The chief motor fibres of the bladder, distributed probably to the longitudinal muscle. (c) Motor fibres of the uterus. ((I) Vaso-dilator fibres of the penis (nrrri eriyentex). (e) Secretory fibres of the prostate gland. THE GREAT PLEXUSES OF THE SYMPATHETIC. Under this head are included certain large plexuses of nerves placed farther forwards in the visceral cavity than the gangliated cords, and furnishing branches to the viscera. The principal of these plexuses are the cardiac, the solar, and the hypogastric with the pelvic plexuses prolonged from it. They are composed of assemblages of nerves, or of nerves and ganglia, and from them smaller plexuses are derived. CABDIAC PLEXUS. This plexus receives the cardiac branches of the cervical ganglia and those of the pneumo-gastric nerves, and from it proceed the nerves which supply the heart, besides some offsets which contribute to the nervous supply of the lungs. It lies against the aorta and pulmonary artery, where these vessels are in contact, and in its network are distinguished two parts, the superficial and the deep cardiac plexuses, the deep plexus being seen behind the vessels, and the superficial more in front, but both being closely connected. The branches pass from these plexuses chiefly forwards in two bundles, accompanying the coronary arteries. Superficial cardiac plexus. — The superficial cardiac plexus (fig. 232) lies in the concavity of the arch of the aorta, between the ligament of the ductus arteriosus and the right branch of the pulmonary artery. In it the superficial or upper cardiac nerve of the sympathetic of the left side terminates, either wholly or in part, together with the lower cervical cardiac branch of the left pneumo-gastric nerve. In the superficial plexus a small ganglion, the ganglion of Wrisberg, is frequently found at the point of union of the nerves. Besides ending in the right coronary plexus, the superficial cardiac plexus furnishes laterally filaments along the pulmonary artery to the anterior pulmonary plexus of the left side. Deep cardiac plexus. — The deep cardiac plexus, much larger than the superficial one, is placed behind the arch of the aorta, between it and the end of the trachea, and above the bifurcation of the pulmonary artery. This plexus receives all the cardiac branches of the cervical ganglia of the sympathetic nerve, except the upper cardiac nerve of the left side. It likewise receives the cardiac nerves furnished by the vagus and by the recurrent laryngeal branch of that nerve, with the exception of the left cervical cardiac nerves. Of the branches from the right side of the plexus, the greater number descend in front of the right pulmonary artery, and join branches from the superficial part in the formation of the right coronary plexus ; others, passing behind the right pulmonary artery, are distributed to the right auricle of the heart, and a few filaments are continued into the left coronary plexus. On the left side, a few branches pass forwards by the side of the ductus arteriosus to join the superficial cardiac plexus, and others descend to the left auricle ; but the great majority end in the left coronary plexus. The deep cardiac plexus sends filaments to the anterior pulmonary plexus on each side. Coronary plexuses. — The right or posterior coronary plexus is derived from both the superficial and deep cardiac plexuses, the filaments by which it arises embracing the root of the aorta. It accompanies the right coronary artery on the heart, sending its branches upwards and downwards to the auricle and ventricle. CARDIAC PLEXUS. 373 The left or anterior coronary plexus is larger than the right, and is derived mainly from the left half of the deep cardiac plexus. Being directed forwards between the pulmonary artery and the left auricular appendage, it reaches the left coronary artery, and subdivides into two principal portions which accompany the primary divisions of that vessel. Nervous filaments ramify in great number under the epicardium, especially on the ventricular portion of the heart. They are not so easily distinguished in man as in some animals. In the heart of the calf or the lamb they are distinctly seen without dissection, running in lines which cross obliquely the muscular fibres. Microscopic ganglia occur on the nerves of the auricles, and in the course of the coronary plexuses, but they are absent from the offsets to the ventricular wall (see Vol. II, Fig. 236. — DIAGRAMMATIC REPRESENTATION OP THE CARDIAC PLEXUS OP THE HUMAN EMBRYO. (W. His, jun. ) a, aorta ; a', pulmonary artery ; b, atrium, with the orifices of the veins ; Au, auricle proper ; v, ventricle ; vg, vagus ; sy, cord of sympathetic ; p, p, pericardium ; s, transverse sinus of peri- cardium ; I, bulbar plexus ; II, atrial plexus ; III, intermediate plexus. From the embryological investigations of W. His, jun., it appears that the ascending aorta, the pulmonary trunk, and the ventricles of the heart are supplied by the upper cardiac nerves, while the auricles receive branches arising- at a lower level. The earliest of the cardiac nerves to be developed are branches from both vagus and sympathetic of each side to the arterial bulb, which appear about the end of the fourth or the beginning of the fifth week of foetal life, and make their way between the aorta and the pulmonary trunk, where they form the bulbar plexus. In the seventh week other nerves are found passing from the vagi lower down to the back of the auricles, and forming there the atrial plexus, which also receives sympathetic branches through the following plexus. The bulbar anel atrial plexuses are connected by branches which descend from the former behind the transverse sinus of the peri- cardium, and are joined by offsets of both vagi, the left recurrent nerve, and the sympathetic cords, the whole constituting the intermediate plexus. All of these branches contain numerous ganglion-cells of sympathetic nature, which travel downwards with the growth of the nerves. In the course of the third month the coronary nerves are developed from the bulbar plexus, and offsets of the atrial plexus spread over the auricles. In the definitive state therefore the bulbar plexus is represented by the superficial cardiac plexus and a part of the deep cardiac plexus, with their coronary offsets, the intermediate plexus by the remainder of the deep cardiac plexus, and the atrial plexus by the network on the auricles. The distribution of the ganglia in the adult heart corresponds to the extent of these plexuses. SOLAR OR EPIGASTRIC PLEXUS. The solar or epigastric plexus (plexus cxliacus), the largest of the prevertebral centres, is placed at the upper part of the abdomen, behind the stomach, and in 374 THE SYMPATHETIC NERVES. front of the aorta and the pillars of the diaphragm. Surrounding the origin of the cceliac axis and the superior mesenteric artery, it occupies the interval between the suprarenal bodies, and extends downwards as far as the pancreas. The plexus Fig. 237. — SOLAR AND AORTIC PLEXCSES, WITH THE LUMBAR PORTION OF THE SYMPATHETIC CORDS, IN THEIR RELATIONS TO THE AORTA, &C. (GK D. T. ) C.A., coeliac axis, and S.M.A., superior mesenteric artery, both cut close to their origin ; surround- ing them is the solar plexus ; on the aorta below the renal arteries is the aortic plexus ; s', great, s", small, and s'", smallest splanchnic nerves ; A, phrenic ganglion ; B, semilunar ganglion ; C, aortico- renal ganglion ; D, superior mesenteric ganglion ; E, spermatic ganglion ; F, inferior mesenteric ganglion. SOLAR PLEXUS. 375 consists of nervous cords, with several ganglia of various sizes connected with them. The large and small splanchnic nerves on both sides, and some branches of the pneumo-gastric, terminate in it. The branches given off from it are very numerous, and accompany the arteries to the principal viscera of the abdomen, constituting so many secondary plexuses on the vessels. Thus, diaphragmatic, cceliac, mesenteric, and other plexuses are recognised, which follow the corresponding arteries. Semiluiiar ganglia. — The solar plexus contains, as already mentioned, several ganglia (ganglia cvdiaca) ; and by the size of these bodies it is distinguished from the other prevertebral plexuses. The two principal ganglionic masses, named semilunar, though they have often little of the form the name implies, occupy the upper and outer part of the plexus, one on each side, and are placed close to the suprarenal bodies, by the side of the cceliac and the superior mesenteric arteries. At the upper end, which is expanded, each ganglion receives the great splanchnic nerve. The lower part of the ganglionic mass, lying over the root of the renal artery, is commonly more or less detached from the rest, and is distinguished as the aortico-renal ganglion ; it is joined by the small splanchnic nerve, and gives origin to the greaterpart of the renal plexus. Another part, lying below and to the right of the origin of the superior mesenteric artery, is named the superior mesenieric ganglion. Diaphragmatic or phrenic plexus. — The nerves composing this plexus are derived from the upper part of the semilunar ganglion, and are larger on the right than on the left side. Accompanying the arteries along the lower surface of the diaphragm, the nerves sink into the substance of the muscle. They furnish some filaments to the suprarenal body, and join with the spinal phrenic nerves. At the right side, on the under surface of the diaphragm, and near the supra- renal body, there is a small ganglion (diaphragmatic or phrenic ganglion), which marks the junction between the phrenic nerves of the spinal and sympathetic systems. From this small ganglion filaments are distributed to the vena cava, the suprarenal body, and the hepatic plexus. On the left side the ganglion is wanting. Suprarenal plexus. — The suprarenal nerves issue from the solar plexus and the outer part of the semilunar ganglion, some filaments being added from the diaphragmatic plexus and one of the splanchnic nerves. They are short, but numerous in comparison with the size of the suprarenal body, which they enter on its inner and posterior part. These nerves consist in great part of white fibres, and are beset with minute ganglia. Renal plexus. — The nerves forming the renal plexus emanate for the most part from the aortico-renal ganglion, but some are added from the solar and aortic plexuses. The renal plexus also receives the termination of the smallest, and some- times filaments from the small splanchnic nerve, as well as a branch from the first lumbar ganglion. The nerves of the plexus are mostly grey, and in their course along the renal artery ganglia of different sizes (renal ganglia) are formed on them. Lastly, dividing with the branching of the vessel, the nerves follow the renal arteries into the substance of the kidney. On the right side some filaments are furnished to the vena cava, behind which the plexus passes with the renal artery ; and on both sides offsets pass to the spermatic plexus, and a filament to the ureter. Spermatic plexus. — This small plexus commences in the renal, but receives in its course along the spermatic artery an accession from the aortic plexus, in which a small spermatic ganglion is often formed at the place where these branches arise. Continuing downwards to the testis, the spermatic nerves are connected with others which accompany the vas deferens and its artery from the pelvis. In the female, the plexus, like the artery, is distributed to the ovary and the uterus. 376 THE SYMPATHETIC NERVES. Cceliac plexus. — This plexus is of large size, and is derived from the fore part of the great epigastric plexus. It surrounds the coeliac axis in a kind of fenestrated sheath, and subdivides, with the artery, into coronary, hepatic, and splenic plexuses, the branches of which form communications corresponding with the arches of the arterial anastomosis. The plexus receives on the left side a considerable offset from the right pneumo-gastric nerve. The coronary plexus is placed with its artery along the small curvature of the stomach, and unites with the nerves which accompany the pyloric artery, as well as with branches of the pneumo-gastric nerves. The nerves of this plexus enter the coats of the stomach, after running a short distance beneath the peritoneum. The hepatic plexus, the largest of the three divisions of the coeliac plexus, ascends with the hepatic vessels and the bile duct, and, entering the substance of the liver, ramifies on the branches of the portal vein and the hepatic artery. Offsets from the left pneumo-gastric nerve join the hepatic plexus at the left side of the vessels. From this plexus filaments pass to the right suprarenal plexus, as well as other secondary plexuses which follow the branches of the hepatic artery. Thus there is a cystic plexus to the gall-bladder; and there are pyloric, gastro-epiploic, and pan- creatico-duodenal plexuses, which unite with coronary, splenic, and mesenteric nerves. The splenic plexus (plexus linealis), continued on the splenic artery and its branches into the substance of the spleen, is reinforced at its beginning by branches from the left semilunar ganglion, and by filaments from the right vagus nerve. It furnishes the left gastro-epiploic and pancreatic plexuses, which course along the corresponding branches of the splenic artery, and, like the vessels, are distributed to the stomach and pancreas. Superior mesenteric plexus. — The plexus accompanying the superior mesenteric artery, whiter in colour and firmer than any of the preceding offsets, is mainly given off from the lower part of the solar plexus and the superior mesenteric ganglion, but it also receives fibres from the right pneumo-gastric nerve at its junction with the cceliac plexus. Surrounding the trunk of the superior mesenteric artery, it divides into secondary plexuses which agree in name and distribution with the branches of that vessel. In their progress to the intestine some of the nerves quit the arteries which first supported them, and are directed forwards in the intervals between the vessels. As they proceed they divide, and unite with lateral branches, like the arteries, but without the same regularity ; they finally pass upon the intestine along the line of attachment of the mesentery. Aortic plexus. — The aortic or intermesenteric plexus (plexus aorticus aldominalis}, placed along, the abdominal aorta, occupies the interval between the origins of the superior and inferior mesenteric arteries. It consists, for the most part, of two lateral cords, which are connected above with the semilunar ganglia and renal plexuses, and extend downwards on the sides of the aorta, meeting in several communicating branches over the front of that vessel. The cords receive branches from some of the lumbar ganglia, and at the spots where these join there are often small ganglionic enlargements, which are more distinct in the infant. Several filaments pass to the root of the inferior mesenteric artery to form the plexus on that vessel, and in connection with these is the inferior mesenteric ganglion, placed below the origin of the artery. The aortic plexus furnishes the inferior mesenteric plexus and part of the spermatic, gives some filaments to the lower vena cava, and ends below in the hypogastric plexus. Inferior mesenteric plexus. — This plexus is derived principally from the left lateral part of the aortic plexus, and closely surrounds with a network the inferior mesenteric artery. It distributes nerves to the left or descending and the sigrnoid HYPOGASTRIC AND PELVIC PLEXUSES. 377 colon, and assists in supplying the rectum. The nerves of this plexus, like those of the superior mesenteric plexus, are firm in texture and of a whitish colour. The highest branches (those on the left colic artery) are connected with the last branches (middle colic) of the superior mesenteric plexus, while others in the pelvis unite with offsets derived from the pelvic plexus. On the branches of the coeliac and mesenteric plexuses Pacinian corpuscles are often present. They are very variable in number, and are not so numerous or regular in man as in the cat. Their most frequent seat is in the loose tissue behind the pancreas. HYPOQASTRIC PLEXUS. The hypogastric plexus, the assemblage of nerves destined for the supply of the viscera of the pelvis, lies, invested in a sheath of dense connective tissue, in the interval between the two common iliac arteries. It is formed by the prolongations of the aortic plexus on each side, which receive considerable branches from the lumbar ganglia, and, after crossing the common iliac artery, interlace in the form of a flat plexiform mass placed in front of the lowest lumbar vertebra. The plexus contains no distinct ganglia. At the lower end it divides into two parts, which are directed downwards, one to each side of the pelvic viscera, and form the pelvic plexuses. PELVIC PLEXUS. The pelvic or inferior hypogasfcric plexuses (fig. 234, pl\ one on each side, are placed in the lower part of the pelvic cavity by the side of the rectum, and of the vagina in the female. The nerves, continued from the hypogastric plexus, enter into repeated communications as they descend, and form at the points of connection small knots, which contain a little ganglionic matter. After descending some way, they become united with branches of the spinal nerves, as well as with a few offsets of the sacral ganglia, and the union of all constitutes the pelvic plexus. The spinal branches which enter into the plexus are furnished from the third and fourth sacral nerves, sometimes also the second. Small ganglia are formed at the places of union of the spinal nerves, as well as elsewhere in the plexus. From the plexus so constituted, numerous nerves are distributed to the pelvic viscera. They correspond in great measure with the branches of the internal iliac artery, and vary with the sex ; thus, besides haemorrhoidal and vesical nerves, which are common to both sexes, there are nerves special to each : — namely, in the male for the prostate, vesicula seminalis, and vas deferens ; in the female, for the vagina, uterus, ovary, and Fallopian tube. The nerves distributed to the urinary bladder and the vagina contain a larger proportion of spinal fibres than those furnished to the other pelvic viscera. Haemorrhoidal plexus. — These slender nerves proceed from the upper part of the pelvic plexus. They join with the nerves (superior haemorrhoidal) which descend with the inferior mesenteric artery, and penetrate the coats of the rectum. Vesical plexus.— The nerves of the urinary bladder are very numerous. They are directed from the lower part of the pelvic plexus to the side and lower part of the bladder. At first these nerves accompany the vesical blood-vessels, but after- wards they leave the vessels, and subdivide into minute branches before perforating the muscular coat of the organ. The lower part of the ureter is also supplied by these nerves ; and secondary plexuses are given in the male to the vas deferens and the vesicula seminalis. The nerves of the vas deferens ramify round that tube, and communicate in the spermatic cord with the nerves of the spermatic plexus. Those furnished to the vesicuta seminalis form an interlacement on the vesicula, and some branches 378 THE SYMPATHETIC NERVES. penetrate its substance. Other filaments from the prostatic nerves reach the same structure. Prostatic plexus. — The nerves of this plexus are of considerable size, and pass between the prostate gland and the levator ani. Some are furnished to the prostate and to the vesicula seminalis ; and the plexus is then continued forwards to supply the erectile substance of the penis, where its nerves are named cavernous. Cavernous nerves of the penis. — These are very slender, and difficult to dissect. Continuing from the prostatic plexus, they pass onwards beneath the subpubic arch and through the muscular structure connected with the membranous part of the urethra, to the dorsum of the penis. At the root of the latter, the cavernous nerves are joined by some short filaments from the pudic nerve. Having distributed twigs to the fore part of the prostate and the membranous part of the urethra, these nerves divide into branches for the erectile substance of the penis, as follows :— The small cavernous nerves perforate the fibrous covering of the corpus caver- nosum near the root of the penis, and end in the erectile substance. The large cavernous nerve extends forwards on the dorsum of the penis, and dividing, gives filaments which penetrate the corpus cavernosum, and pass with or near the cavernous artery. As it continues onwards, this nerve joins with the dorsal branch of the pudic nerve about the middle of the penis, and is distributed to the corpus cavernosum. Branches from the foregoing nerves reach the corpus spongiosum urethras. The cavernous nerves are composed mainly of pale fibres. Vaginal nerves. — The nerves furnished to the vagina leave the lower part of the pelvic plexus — that part with which the spinal nerves are more particularly combined. They are distributed to the vagina without previously entering into a plexiform arrangement ; and they end in the erectile tissue on the lower and anterior part, and in the mucous membrane. Nerves of the uterus. — These nerves are derived mainly from the lateral fasciculus prolonged to the pelvic plexus from the hypogastric plexus, but some filaments are also added from the third and fourth sacral nerves. They are directed upwards with the blood- vessels, between the layers of the broad ligament, along the side of the organ, and some slender filaments accompany the branches of the uterine artery, but the larger number of the nerves sink directly into the substance of the uterus, penetrating for the most part its neck and the lower portion of its body. They form connections in the broad ligament with the ovarian nerves, and the fundus of the uterus also receives an offset from that plexus. Numerous small ganglia are contained in the plexus by the side of the neck of the uterus, and a cluster of these constitutes the ganglion cervicale of Frankenhfiuser. They appear to be absent in the muscular substance of the organ. One branch continued directly from the common hypogastric4plexus, reaches the hinder surface of the body of the uterus above the rest ; and a nerve from the same source ascends to the Fallopian tube. The nerves of the gravid uterus have been frequently investigated, with a view to discover if they become enlarged along with the increase in size of the organ. It is ascertained that the increase which takes place is confined, for the most part, to the thickening of the fibrous envelopes of the nerves ; but it is stated also that fibres furnished with a medullary sheath, which in the un impregnated state of the uterus lose that sheath as they proceed to their distribution, in the impregnated condition of the uterus continue to be surrounded with it as they run between the muscular fibres (Kilian). LITERATURE. 379 BE CENT LITERATURE OF THE SYMPATHETIC. Alpig-er, M., A natomische Studie iibcr dasgegenscitige Verhalten der Vagus- und Sympathicusdste im Gcbicte des Kehlkopfes, Langenheck's Archiv, xl, 1890. Bayliss, "W. M., and Bradford, J. B,., The Innervation of the Vessels of the Limbs, Journ. Physio!., xvi, 1894. Bayliss, W. M., and Starling:, E. H., On the Origin from the Spinal Cord of the Vaso- constrictor Nerves of the Portal Vein, Journ. Physiol., xvii, 1894. Bechterew, "W., u. Mislowski, N., Ueber centrale und pcriphere Darminnervation, Arch. f. Physiol., Supplt. Bd., 1889 ; Zur Frage iiber die Innervation des Magens, Neurolog. Centralbl., 1890. Bonuzzi, P., Ueber Vasodilatatorcn in den hinteren Riickenmarkswurzeln, Wiener Jahrbiicher, 18S5. Bradford, J. B,., The Innervation of the Renal Blood-Vessels, Journ. Physio!., x, 1889. Bradford, J. R., and Dean, H. P., The Pulmonary Circulation, Journ. Physiol., xvi, 1894. Braunstein, E. P., Zur Lehre von der Innervation der Pupillenbewegung, Wiesbaden, 1894. Cavazzani, A., L' inncrvazione vaso-motrice dei polmoni, Rivista veneta d. sc. med., 1891, and Arch. ital. de biol., xvi, 1891. Dastre, B., et Morat, J. P., Le systeme grand sympathique, Bull, scient. du depart. duNord, 1880 ; Sur I' experience du grand sympathique cervical, & Sur les nerfs vaso-dilatateurs des parois de la bouche, Comptes rendus, xci, 1880 ; Sur lafonction vaso-dilatatrice du nerf grand-sympathique, Arch, de physiol. norm, et pathol., 1882 ; Les nerfs vaso-dilatateurs de Voreille externe, Arch, de physiol. norm, et pathol., 1882 ; Sur les nerfs vaso-dilatateurs du membre inferieur, Arch, de physiol. norm, et pathol., 1883 ; Du rdle tonique et inhibitoire des ganglions sympathiques, et de leur rapport avec les nerfs vaso-moteurs, Comptes rendus, xcvi, 1883 ; Contribution d V etude des ganglions sympathiques ; leur role tonique et inhibitoire; leur rapport avec les nerfs vaso-moteurs, C. r. hebd. d. 1. Soc. d. biol., 1883; Recherches experimental sur le systeme nerveuie vaso-moteur, Paris, 1884. Doyon, M., Recherches sur les nerfs vasomoteurs de la retine, Arch, de physiol. norm, et pathol., 1890 and 1891. Drobnik, T., Topographisch-anatomische Studien uber den ffalssympathicus, Arch. f. Anat., 1887. Edg-eworth, F. H., On a large-fibred Sensory Supply of the Thoracic and Abdominal Viscera, Journ. Physiol., xiii, 1892. Ehrmann, S., Ueber die Innervation des Diinndarms, Wiener Jahrbiicher, 1885. Eisenlohr, L., Ueber die N erven- und Ganglienzellen des menschlichen Uerzens, nebst Bemer- kungen zitr pathologischen Anatomic derselben, Inaug. Diss., Miinchen, 1887. Fellner, L., Die Bewegunys- und Ilemmungsti erven des Rectums, Wiener Jahrbiicher, 1883 ; Weitere Mittheilungen ueber die Bewegungs- und ffemmungsnerven des Rectums, Arch. f. d. gesammte Physiologic, Ivi, 1894. Prancois-Franck, Recherches sur rinnervation vaso-motrice du penis, Arch, de Physiol. norm, et pathol., 1895. Gaskell, "W. H., " On the Structure, Distribution and Function of the Nerves which innervate the Visceral and Vascular Systems," Journ. Physiol., vii, 1886 ; Do the Nervi Erigentes leave the Spinal Cord in Anterior or Posterior Roots? Proc. Physiol. Soc., Jan. 15, 1887, Journ. Physiol., viii. G-aule, J., Versuch eines Schemas der Innervation der J3lase, insbesondere der localen Reftex- bahnen, Arch. f. Physiol., Supplt. Bd., 1892. G-ehuchten, A. v., Les elements nerveux moteurs des racines postericures, Anatom. Anzeiger. viii, 1893. G-uepin, A., Sur I'innervation vesicale, Journ. de TAnat. et de la Physiol., 1892. His, "W., Histogenese und Zusammenhang der Ncrvenelemente, Verhandlg. d. x. Internat. Med. Congresses. Berlin, 1890, and Arch. f. Anat., Supplt. Bd., 1890. (Development of Sympathetic.) His, W., junr., Die Entwickelung des fferznervensy stems bei Wirbelthieren, Abhandlg. d. konigl. sachsisch. (resellsch. d. Wissensch., 1891. Jastreboff, N. W., On the Normal and Pathological Anatomy of the Gang'ion Cervicale Uteri. Trans. Obstetr. Soc., London, xxiii, 1881. Jegorow, J., Ueber den Eirtfluss der langen Ciliarnerven auf die Erweiterung der Papille, Arch, f. Physiol., 1886 ; Zur Lehre von der Inner-cation der Blutgefasse, Arch. f. Physiol., Supplt. Bd., 1892. Kasem-Beck, A., Zur Kenntniss der Herznerven, Arch. f. mikrosk. Anat., xxiv, 1884 ; Ueber das Vorkommen von Ganglien und einzelnen Nervenzellen auf den Hcrzventrikeln der Menschen, der Sdugethiere und der Vogel, Centralbl. f. d. med. Wissensch., 1887. Keng1, Lim Boon, On the Nervous Supply of the Dog's Heart, Journ. Physiol., xiv, 1893. Kolliker, A. v., Der fcinere Bau und die Functionen des sympathischen Nervensy stems, Wurzburger Sitzungsberichte, 1894 ; Ueber diefeinere Anatomic und die physiologische Bedeutung des sympathischen Nervensy stems, Verhdlgn. d. Gres. d. deutschen Naturf. u. Aerzte, 1894. Kiihlwetter, E., Zur Lehre von der Lagerung der Gefdssnerven in den Wurzeln der RucTcen- marksnerven, Eckhard's Beiti-'age z. Anatom. u. Physiol., xi, 1885. Lang-endorff, O., Die Beziehungen der Ncrvcnfasern des Halssympathicus zu den Ganglienzellen des oberen Ilalsknotens, Centralbl. f. Physiologic, v, 1891. 380 THE SYMPATHETIC NERVES. Lang-ley, J. N., The Innervation of the Pelvic Viscera, Proc. Physiol. Soc., Dec. 13, 1890, Journ. Physiol., xii ; On the Course and Connections of the Secretory Fibres supplying the Sweat-Glands of the Feet of the Cat, Journ. Physiol. , xii, 1891 ; On the Origin from the Spinal Cord of the Cervical and upper Thoracic Sympathetic Fibre*, with some Observations on White and Grey Rami Communicantes, Phil. Trans., 1892 ; On the Larger Medullated Fibres of the Sympathetic System, Journ. Physiol., xiii, 1892 ; On an "Accessory" Cervical Ganglion in the Cat and Notes on the Rami of the Superior Cervical Ganglion ; also Notes on the Cervical Sympathetic, and chiefly on its Vaso-motor Fibres, Proc. Physiol. Soc., Jan. 21, 1893, Journ. Physiol., xiv : The Arrangement of the Sympathetic Nervous System, based chiefly on Observations upon Pilo-motor Nerves, Journ. Physiol., xv, 1893 ; Further Observations on the Secretory and Vaso-motor Fibres of the Foot of the Cat, with Notes on other Sympathetic Nerve Fibres, Journ. Physiol., xvii, 1894. Lang-ley, J. N., and. Anderson, H. K., On Reflex Action from Sympathetic Ganglia, Journ. Physiol., xvi, 1894 ; The Constituents of the Hypogastric Nerves (cat), Journ. Physiol., xvii, 1894. Langley, J. N., and Dickinson, "W., On the Lofal Paralysis of Peripheral Ganglia, and on the Connexion of different Classes of Nerve Fibres with them, Proc. Roy. Soc., xlvi, 1889. Lang-ley, J. N., and Sherring-ton, C. S., On Pilo-motor Nerves, Journ. Physiol., xii, 1891. Lenhossek, M. v., Ueber Nervenfasern in den hinteren Wurzeln, welche aus dem Vorderhorn entspringen, Anatom. Anzeiger, v, 1890. Mall, F., Die motor ischen Nerven der Portalvene, Arch. f. Physiol., Suppl. Bd., 1890; Der Einfluss des Systems der Vence Portce avf die Vertheihing des Blutes, Arch. f. Physiol., 1892. Morat, J. P., Recherches sur les vaso-moteurs de la tete, Arch, de physiol. norm, et pathol. , 1889; Les nerfs vaso-dilatateurs et la loi de Magendie, Arch, de physiol. norm, et pathol., 1890; Recherches sur les nerfs vaso-moteurs de la tete. Trajet intracrdnien des vaso moteurs auriculaires, Arch, de physiol. norm, et pathol., 1891 ; Origines et centres trophiques des nerfs raso-dilatateurs, Comptes rendus, cxiv, 1892 ; Les fonctions vaso-motrices des racines posttrieures, Arch, de physiol. norm, et pathul., 1892 ; Sitr quelques particularity de I'innervation motrice de Vestomac et de Viittestin, Arch, de physiol. norm, et pathol., 1893. Morat, J. P., et Doyon, M., Le grand sympathique, nerf de I' accommodation pour la vision des objets eloignes, Comptes rendus, cxii, and Arch, de physiol. norm, et pathol., 1891. Nawrocki, P., und Przybylski, Die pupillenerweiternden Nerven der Katze, Arch. f. d. gesammt. Physiol., 1, 1891. Nawrocki, P., und Skabitschewsky, B., Ueber die motorischen Nerven der Blase, Arch. f. d. gesammt. Physiol., xlviii, 1891 ; Ueber die sensiblen Nerven deren Reizung Contraction der Blase hervorruft, Arch. f. d. gesammt. Physiol., xlix, 1891. Onodi, A. D., Ueber das Verhdltniss der cerebrospinalen Faserbundel zum sympathischen Grenzstrange, Med. Centralbl., 1883, and Arch. f. Anat., 1884; Ueber die Entwicklung der Spinal- ganglien und der Nervenwurzeln, Internat. Monatsschr. f. Anat. u. Histol., 1884 ; Ueber die Entwicklung des sympathischen N ervensystems, Arch. f. mikroskop. Anat., xxvi, 1885. Oser, L., Ueber die Innervation des Pylorus, Wiener Jahrbticher, 1884; Experimentelle Beitrdge zur Innovation des Magens, Zeitschr. f. Klin. Med., xx, 1892. Pal, J., Ueber die Hemmungsnerven des Darmes, Wiener klin. Wochenschrift, 1893. Paterson, A. M., The Development of the Sympathetic Nervous System in Mammals, Proc. Roy. Soc., xlviii, 1890, and Phil. Trans., 1890. Przybylski, Sur les nerfs dilatateurs de la pupille cJiez le chat, Arch, slaves de Biologic, ii, 1887. Rein, G., Beitrag zur Lehre von der Innervation des Uterus, Arch. f. d. gesammte Physiol., xxiii, 1880 ; Note sur le plexus nerveux fondamental de Vuterus, C. R. Soc. de Biol., 1882. Remy, Ch., Nerfs ejaculateurs, Journ. de 1'anat. et de la physiol., 1886. Romberg-, E., Zur Frage der II erzganglicn, Centralbl. f. Physiol., iv, 1891. Sherringrton, C. S., Journ. Physiol., xiii, 1892 (p. 702, Pupillo-dilator fibres in monkey ; p. 676, Nerves of bladder) ; ib., xvii, 1894 (p. 217, Efferent fibres in posterior roots of spinal nerves) ; see also Langley and Sherrington. Sperino, Gr., Sulla presenza di cellule ganglionari sul decorso delle fiore die compongono i nervi splanchnicus major ed minor, Grazz. Osp. , 1886. Steil, A., Ueber den spinalea Ursprung des Halssympathicus, Arch. f. d. gesammt. Physiol., Iviii, 1894. Stein ach, E.. Die motorische Innervation des Darmtractus durch die hinteren Spinalnerven- wurzeln, Lotos, xiv, 1893. Thompson, W. H., Ueber die AbhdngigTceit der Gliedervenen von motorischen Nerven, Arch. f. Physiol., 1893. Varoglia, S., e Conti, A., Alcune particolarita macro- e microscopiche dei nervi cardiaci nelV uomo, Atti della R. Accad. d. Sc. di Torino, xxii, 1887 ; Sur la presence de cellules nerveuses le long des nerfs cardiaques et dans quelques autres nerfs de I'homme, Arch. ital. de biologic, ix, 1887. Vas, F., Ueber die Bedeutung der grossen Ganglien im sympathischen Grenzstrange, Allgem. Wiener med. Zeitung, 1891. White, W. Hale, On the Histology and Function of the Mammalian Superior Cervical Ganglion, Journ. Physiol., viii, 1887 ; Further Observations on the Histology and Function of the Mammalian Sympathetic Ganglia, Journ. Physiol., x, 1889. Zeglinsky, N., Experimentelle Untersuchung uber die Irisbewcgung, Arch. f. Physiol., 1885. Zeissl, M. v., Ueber die Innervation der Blase, Arch. f. d. gesammte Physiol., liii, 1893, and Iv, 1894. MORPHOLOGY OF NERVES. 381 T MORPHOLOGY OF THE PERIPHEKAL NERVES. SPINAL NERVES. — Segmentation. — The spinal nerves in their arrangement as they leave the vertebral column exhibit in a marked degree the character of segmentation. This is not the case however at their attachment to the spinal cord, where the filaments of both the anterior and posterior roots form each a nearly continuous series along the whole length of the cord. In their connection with the grey matter of the spinal cord there is again evidence of a segmental arrangement, which appears not to correspond exactly to the segmentation seen in the nerve-trunks, for it seems probable that the fibres composing one posterior root, for example, may be connected with more than one segment of the spinal cord (cf. p. 350). Mode of division. — A typical segmental nerve, on leaving the vertebral canal, divides at once into two parts, which are known as the anterior or central, and the posterior or dorsal Fig. 238. — PLAN OF THE MODE OF BRANCHING OF A SEGMENTAL NERVE. primary f/icixio/i*. In addition to these, the trunk also gives off a small recurrent or meningeal branch to the interior of the spinal canal, and the anterior division furnishes a branch to the sympathetic. The primary branching of the nerve may thus be looked upon as a separation into four parts, of which the anterior, posterior, and recurrent divisions are said to be somatic, while the offset to the sympathetic is usually called visceral or splanchnic (rainu* vtieeralis). The latter term, although often convenient, is, however not strictly accurate, since the sympathetic division contains, in addition to visceral fibres, other fibres which influence the unstriped muscles of the vessels and skin of the trunk and limbs, parts which are of somatic origin. Posterior primary divisions. — These supply the dorso-lateral muscle (see Vol. II, p. 347) and the overlying integument. As a rule, each is divided into internal and external branches Fig. 239. — PLAN OF AN UPPER DORSAL NERVE, SHOWING THE TYPICAL MANNER OF BRANCH- ING OF THE ANTERIOR AND POSTERIOR PRIMARY DIVISIONS OF A SEGMENTAL NERVE. (GKD. T.) corresponding to the cleavage of the dorso- lateral muscle, and from one only of these an offset passes to the skin. The first cer- vical nerve has no external branch or cutaneous offset ; while the last two sacral and the coccygeal nerves give off no muscu- lar branches, as the dorso-lateral muscle terminates at the fourth sacral vertebra, and therefore they do not divide into the usual two branches. As has been previously pointed out (p. 341), cutaneous branches are not usually furnished by those nerves, the anterior divisions of which occupy a central position in the limb-plexuses (lower cervical and lower lumbar nerves). Anterior primary divisions. — In the primitive condition the anterior primary division of a segmental nerve supplies the ventro-lateral muscle of the segment and a corresponding zone of skin. The cutaneous or perforating branches are two in number, a lateral, which again divides into anterior and posterior branches, and an anterior. This arrangement is however retained only in the nerves from the second dorsal to the first lumbar inclusive. Above and below the region thus indicated the primitive condition is much modified by the union of the nerves in plexuses, in great part for the supply of the limbs. But the cutaneous distribution of each of these nerves, as has already been shown (p. 345), is to a definite continuous area of skin, altered in shape and position in consequence of growth-changes, and in the case of the central limb-nerves shifted so much that all connec- tion with the trunk is lost. VOL. III., PT. 2. » B 382 MORPHOLOGY OF NERVES. Nerves of the limbs. — As to the morphological nature of the limb-nerves, it is held by Paterson, Eisler, and others that they represent the whole of the anterior primary divisions of segmental nerves, but it seems probable that the view enunciated by Goodsir, namely, that the limb-nerves are greatly developed lateral perforating1 branches of segmental nerves, is the better founded. At the same time it is to be noticed that the increase of the lateral branch for the supply of the limb is accompanied by a reduction of the other portions of the segmental nerve, which proceeds so far that the anterior and posterior cutaneous offsets, as well as the visceral branch, are all wanting- in the case of the central nerves of the limb- plexuses. The transition from the typical segmental nerves to the modified form met with in the limbs takes place gradually, and may be thus traced. The third dorsal nerve has the typical character ; the second differs but little, its posterior cutaneous branch is drawn out over the scapula, and its lateral perforating branch becomes enlarged and extends down the arm. forming a connection with the brachial plexus, while some of the fibres belonging to this division often begin to take a shorter course to the plexus through the communication with the first dorsal nerve (p. 307). In the first dorsal nerve the lateral branch, greatly enlarged, passes directly into the brachial plexus, the anterior and posterior cutaneous offsets are small, and sometimes wanting, and its contribution to the sympathetic is less than that of the second. The eighth, seventh and sixth cervical nerves consist almost wholly of large lateral offsets, the anterior and posterior perforating, and the visceral branches are suppressed, and the supply from the anterior primary division to trunk-muscles is represented only by the twigs to the scaleni and longus colli. With the fifth cervical nerve the posterior cutaneous branch reappears ; and in the fourth, third, and second nerves the lateral offsets are freed from the limb-plexus (except the fourth to a slight extent in some cases), and furnish the super- ficial branches of the cervical plexus, the lower of which are however drawn out over the root of the limb, while anterior perforating branches are wanting. At the lower part of the trunk, the twelfth dorsal and first lumbar nerves have the charac- teristic segmental disposition, but their posterior and lateral perforating branches are drawn down over the root of the limb, as is the case also to a slight extent with a part of the anterior perforating branch of the first lumbar (ilio-inguinal nerve), while a small part of the fibres of this nerve often passes into the limb-plexus. The second lumbar nerve is distinctly inter- mediate in character, since it possesses all the branches of a segmental nerve, although its larger part passes into the limb-plexus. Its anterior perforating branch is represented by the genital division of the genito-crural, and its lateral cutaneous offset by the fibres passing to the crural division of the genito-crural and to the external cutaneous nerve. The third lumbar nerve has a posterior perforating offset, but it consists mainly of a large lateral division passing into the plexus ; an anterior perforating branch is wanting, and the contribu- tion to the sympathetic is very small or absent. The fourth lumbar is purely a limb-nerve, the posterior and anterior cutaneous and the visceral offsets being suppressed. The fifth lumbar is like the fourth, except that it may have a small posterior cutaneous offset ; and this branch is regularly present in the succeeding nerves. With the second sacral nerve the con- tribution to the limb-plexus diminishes, the visceral branch reappears, the lateral cutaneous branch begins to be more independent in the small sciatic and perforating cutaneous nerves, and the continuation of the trunk to form an anterior perforating offset is to be recognized in the pudic nerve. The third sacral furnishes only a small contribution to the limb-plexus, and both it and the fourth sacral have the usual constitution of segmental nerves, but their anterior primary divisions are more or less closely united in the pudic nerve. Of the branches of the latter, the inferior hasmorrhoidal probably corresponds to a lateral perforating offset, while the perineal division and the dorsal nerve of the penis represent anterior perforating offsets. In the foregoing sketch it has been shown that the lateral divisions of the nerves are enlarged and carried outwards to supply the integument of the limbs. The cutaneous offsets of some of the posterior primary divisions are also drawn out to a slight extent over the roots of the limbs (especially the lower), but they do not enter into the plexuses. The anterior perforating branches however are not extended to the limbs, except the first lumbar to a slight degree where the lower limb impinges upon the area of these nerves. The supply of the muscles of the limbs by lateral divisions of spinal nerves offers no difficulty, since these muscles are derived from the superficial layer of the great ventro-lateral muscle (see Vol. II, p. 274), and the obliquus externus, the sole trunk-muscle of this layer (the pectorales, serratus magnus, latissimus dorsi, superficial petrosal branch and the efferent part of the chorda tympani), and in the third nerve (ciliary portion). The origin of the splanchnic efferent fibres in the spinal cord has not, been determined, but in the brain-stem there are special nuclei from which the fibres of this group arise. These are the bulbar portion of the accessory nucleus (in part), the small-celled vago-glosso-pharyngeal nucleus, from which not only the splanchnic efferent fibrefc of t he vagus and glosso-pharyngeal proceed, but according to Duval also those of the facial through the portio intermedia, and the groups of smaller cells at the upper end of the oculomotor nucleus (see Part 1 of this Volume, p. 99). Somatic afferent film's constitute the greater part of the large root of the fifth nerve and the auditory nerve ; and a small group of these fibres occurs also in the vagus, composing its auricular branch. S/)laneli »i<- afferent Jibnx are contained in the facial (afferent part of the chorda tympani), glosso-pharyngeal and vagus nerves, probably also in the sensory purl, of tin- fifth nerve. With regard to the central connections of these fibres it is to be remarked that many of them descend in the bulb and upper part of the spinal cord, forming the so-called " ascending roots " — the funiculus solitarius for the vagus and glosso-pharyngeal, perhaps also for the portio intermedia, and the bulbar root of the fifth nerve. A great number of the fibres enter the auditory nuclei, the sensory nucleus of the fifth nerve and the siibstant ia grlatinosa, which may be looked upon as derivatives of the posterior horn of the grey substance of the cord, just as the nerves at their attachment to the brain-stem form a series continuing the 1 According to Hatschek there are also ventral roots to the glosso-pharyngeal and vagus nerves in Ammoctt'tes, anil the same have been described in the embryo of man and the rabbit by Zimmermann. CONSTITUTION OK CRANIAL NKKYIX 387 lino of I !'<• |H, I -ri-ir ruol.s. Tin- ;iM'«-rcnt, fibres, l>oMi . nm.'il i<- :in> ^ « S a S q S .2 1 Q ~< g Splanchnic afferent. 1 Superior and ini Portio intermedia, afferent part. 1 Glosso- phary ngeal , fibres to f uniculus solitarius. Vagus, fibres to f uniculus solitarius. 1 M M H § CS To 1 5 | 8 "S £ ft ^2 0 g 1 1 1 I ^ 1 > P4 K 1 i III | to H^ • | g | ' 1 S H • •S +H s S «C E g^ CO H g Splanchnic I 8 I 111! lifi I 11 I1 aij w''c? 'o |Is a w § Eb 0 3 1 Lateral .somatic efferent. Ocular facial? | i i Glosso-pharyngeal, fibres from nucleus ambiguus. Vagus, fibres from nucleus ambiguus. o ^| 0 O1 PQ o B *• 1! | | d 1 1 1 1 •1 o J •o • S ft ; * O " -, m w x 1 1 H S o 1 £ CO 0 M FOURTH H g pS g a fc 1 1 GO CO 1 g H 55 I OQ 390 MORPHOLOGY OF NERVES. Course and distribution. — While it is obvious that in the distribution of the cranial nerves the segmental arrangement, if it ever existed, has been in many cases greatly modified, there are certain striking1 relations between the course and distribution of some of these nerves and the developmental subdivisions of the head. The distribution of the third, fourth, and sixuh nerves to the muscles of the first three somites has already been pointed out. The nasal branch of the ophthalmic division of the fifth is the nerve of the fronto-nasal process. The inferior maxillary is the nerve of the mandibular arch, its motor root supplying- the muscles of that arch (Vol. II, p. 349), and its sensory part extending by its splanchnic lingual branch into the part of the tongue which is formed from the tuberculum impar in the concavity of the arch. The superior maxillary nerve is the offset furnished by the more primitive mandibular nerve to the maxillary process. The three divisions of the fifth supply the skin externally, and the mucous membrane inter- nally, of their respective portions of the face ; and they send dorsal branches — supraorbital and supratrochlear, temporo-malar, and auriculo-temporal — to ramify over the neural cavity in the same way as the posterior divisions of the spinal nerves, the cutaneous area of which they continue anteriorly. The facial is the nerve of the hyoid arch, supplying the muscles of that arch — stapedius, posterior belly of digastric, and stylo-hyoid — and the system of cutaneous muscles which according to Rabl take their origin in that arch (Vol. II, p. 349). The glosso-pharyngeal is the nerve of the third cephalic visceral (first branchial) arch, in which it runs to the root of the tongue, but its lingual distribution extends considerably beyond the part which is formed from that arch. It also supplies the muscle of the third arch — the stylo-pharyngeus. The vagus is a complex nerve. Its auricular branch, somatic in nature, is the diminished representative of a largely developed somatic portion in fishes, known as the " lateral branch." The superior laryngeal is the nerve of the fourth visceral (second branchial) arch, and the inferior laryngeal of the fifth (third branchial) arch, the latter being drawn down so as to acquire its recurrent character by the shifting of the arteries during development. The remaining portion of the vagus extends far beyond the limits of the head, and supplies nearly the whole of the alimentary canal with its derivatives, and other abdominal organs, the greater part of which, it is to be noted, are developed from the f oregut or cephalic segment of the enteric cavity. The accessory part of the spinal accessory in its distribution cannot be separated from the vagus ; and the spinal portion of the same nerve is not morphologically cranial, but entirely spinal both in origin and distribution. Lastly, the hypoglossal nerve, also spinal originally, is distributed to tongue-muscles, which are also foreign to the head, being probably derived from the longitudinal system of the ventral muscles of the trunk (Vol. II, p. 348). It is thus in series with the upper cervical nerves supplying the muscles of the front of the neck, and the connection that is formed between the hypoglossal and these nerves, giving rise to the ansa cervicalis, &c., may be regarded as representing a prolongation of the cervical plexus. LITERATUBE OF THE MORPHOLOGY OF THE PERIPHERAL NERVES. Adolphi, H., Ueber Variationen der Spinalnerven und der Wirbelsdule anurer Amphibicn, Morphol. Jahrh., xix, 1892. Beard, J., The Ciliary or Motoroculi Ganglion and the Ganglion of the ophthalmicus profundus in Sharks, Anatom. Anzeiger, ii, 1887. Bolk, "L., Beziehungen zwischen SMet, Musculatur und N erven der- Extremitdten, dargelegt am Betkengurtel, an dessen Musculatur •, sowie am Plexus lumbo-sacralis, Morphol. Jahrb., xxi, 1894. Davidoff, M., Ueber die Varietdlen des Plexus lumbo-sacralis von Salamandr a maculosa, Morphol. Jahrb., ix, 1884. Eisler, P., Der Plexus lumbo-sacralis des Menschen, Abhandlg. d. Naturforsch. Gesellsch. zu Halle, 1892. Ewart, J. C., On the Cranial Nerves of Elasmobranch Fishes, Proc. Roy. Soc , xlv, 1889 ; On the Development of the Ciliary or Motor Oculi Ganglion, and The Cranial Nerves of the Torpedo, Proc. Roy. Soc., xlvii, 1890. Froriep, A,, Ueber ein Ganglion des ffypoglossus und Wirbelanlagen in der Occipitalregion, Arch. f. Anat., 1882 ; Ueber Anlagen von Sinnesorganen am Facialis, Glosso-pharynyeus und Vagus, iiber die genetische Stettung des Vagus zum Hypoglossus, und iiber die Herlcunft der Zungenmusculatur, Arch. f. Anat., 1885 ; Ueber das JJomologon der Chorda tympani bei niederen Wirbeltieren, Anatom. Anzeiger, ii, 1887 ; Zur Frage der sogenannten Ncuromerie, Verhandlg. d. anatom. Gesellsch., 1892. Furbringer, M., Zur Lchre von den Umbildungen der Nervenplexus, Morphol. Jahrb., v, 1879. G-askell, W. H., On the Structure, Distribution, and Function of the Nerves which innervate the Visceral and Vascular Systems, Journ. Physiol., vii, 1886 ; On the Relation between the Structure, Function and Distribution of the Cranial Nerves, Preliminary Communication, Proc. Roy. Soc., xliii, 1888 ; On the Relation between the Structure, Function, Distribution and Origin of the Cranial Nerves; together with a Theory of the Origin of the Nervous System of Vertebrata, Journ. Physiol., x, 1889. LITERATURE. 391 Geg-enbaur, C., Die Metumcrie des Kopfes und die Wirbeltheorie des Kopfskelctes, Morphol. Jahrb., xiii, 1887. Hatschek, B., Die Metamerie dcs Amphioxus und des Ammocceten, Verhandlg. d. Anatom. Gesellsch., 1892. Hill, A., The Plan of the Central Nervous System, Cambridge, 1S85; The Grouping of the Cranial Nerves, Brain, 1888. His, "W., Ucber die Anf tinge des pcripherixchcn N erven systems, Arch. f. Anat. , 1879 ; Ucber das A ujtreten der weissen Substanz und der Wurzelfasern am Riickenmark menschlicher Embryonen, Arch, f. Anat., 1883 ; Zur Geschichte des menschlicher* Ruckenmarkes und der Nervenwurzeln, Abhandlg. d. Kgl. Sachs. Gesellsch., 1886 ; Zur Geschichte des Gehirns, sowie der centralen und peripherischen Nervenbahnen beim menschlichen Embryo, Abhandlg. d. Kgl. Sachs. Gesellsch., 1888 ; Die Entivick- lung der crsten Nervenbahnen bcim menschlichen Embryo, Ucbersichtliche DarsteUung, Arch. f. Anat., 1887 ; Die morphologische Betrachtung der Kopfnerven, Arch. f. Anat., 1887 ; Histogenese und Zusammenhang der Nerrenelemente, Verhandlg. d. x internat. med. Congresses, Berlin, 1890, and Arch. f. Anat., Supplt. Bd., 1890. His, W., jun., Zur Entwickelungsgcschichte des A custico-facialis Gebietes beim Mcnschcn, Arch, f. Anat., Supplt. Bd., 1889 ; Die Entivickdung des Hcrznervensy stems bei Wirbelthieren, Abhandlg. d. Kgl. Sachs. Gesellsch., 1891. Hoffmann. C. K., Zur Eatwickclungsgeschichte des Sclachierkopfes, Anatom. Anzeiger, ix, 1894. Holl, M., Uebcr die Lendennerven, Wiener Jahrbiicher, 1880. Jhering, H. v., Das peripherische Ncrvensystem der Wirbelthiere ah Grundlage fur die Kcnntniss der Rcyionenbildung der Wirbelsaule, Leipzig, 1878. Kupffer, C. v., Die Entivickelung der Aopfnerven der Vertebraten, Verhandlg. d. anatom. Gesellsch., 1891. Marshall, A. Milnes, The Segmental Value of the Cranial Nerves, Journ. Anat., xvi, 1882. Martin, P., Die Entwickdung des neunten bis zwolften Kopfnerven bei der Katze, Anatom. Anzeiger, vi, 1891. Paterson, A. M., The Morphology of the Sacral Plexus in Man, Journ. Anat., xxi, 1887 ; The Liinh- Plexuses of Mammals, Journ. Anat., xxi, 1887 ; On the Fate of the Muscle-Plate, and the Development of the Spinal Nerves and Limb-Plexuses in Birds and Mammals, Quarterly Journ. Microscop. Sci. , xxviii, 1887 ; The Position of the Mammalian Limb, regarded in the light of its Innervation and Development, Journ. Anat., xxiii, 1889 ; The Origin and Distribution of the Nerves to the Loiver Limb, Journ. Anat., xxviii, 1894. Rabl, K., Zur Bildungsgeschichte des Halses, Prager med. Wochenschr. , 1886 ; Ueber das Gebiet des N. facialis, Anatom. Anzeiger, ii, 1887 ; Ueber die Metamerie des Wirbeltierkopfes, Verhandlg. d. anatom. Gesellsch., 1892. Rug-e, G., Der Verkurzungsprocess am Rumpfe von Halbaffen, Morphol. Jahrb., xviii, 1892; Zvugnisse fur die metamere Verkurzung des Rumpfes bei Saugethieren. Der Musculus rectus thoraco- abdominalis bei Primaten, Morphol. Jahrb., xix, 1892 ; Verschiebungen in den Endgebieten derNerven des Plexus lumbalis der Primaten, Zeugnissefur die metamere Verkurzung des Rumpfes bei Saugethieren, Morphol. Jahrb., xx, 1893. Schwaltoe, G-., Das Ganglion oculomotorii, Jenaische Zeitschr. f. Naturwiss., xiii, 1879. Sherr ing-ton, C. S., Notes on the Arrangement of some Motor Fibres in the Lumbo- sacral Plexus, Journ. Physiol., xiii, 1892 (p. 708, Significance of limb-plexus). Shore, T. W., The Morpholojy of the Vagus Nerve, Journ. Anat, xxii, 1888 ; On the Minute Anatomy of the Vagus Nerve in Selachians, with remarks on the Segmental Value of the Cranial Nerves, Journ. Anat., xxiii, 1889. Utschneider, A., Die Lendennerven der Affen und des Menschen, Miiuchener medicinische Abhandlungen, 1892. v. Wijhe, J. "W., Ueber die Mesodermsegmenteund die Entwickelung derNerven des Selachierkopfes, Natuurk. Verb, der Koninkl. Akad., Amsterdam, 1882 ; Ueber S >mit"n und N erven im Kopfe von Vogel und Reptilienembryonen, Zoolog. Anzeiger, 1886. Zimmermann, W., Ueber die Metamerie dcs Wirbeltierkopfes, Verhandlg. d. anatom Gesellsch., 1891. INDEX AND GLOSSAEY TO VOL. III., PT. II. ABDOMEN, nerves to muscles of, 352 Abdominal branch of ilio-hypogastric, 315 intercostal nerves. 310 splanchnics, 367 viscera, afferent nerves of, 370 Abducent nerve. See NERVE. Accelerator fibres of heart, 367, 369 Accessory nerve. See NERVE. Acoustic ganglion, 256, 387, 388 Acromio-clavicular joint, nerves of, 293, 294 Afferent nerves. See NERVES. Alveolar nerves, 239, 240, 247 Ampullary nerves, 257, 258 Ankle-joint, nerves of, 332, 333, 335, 337, 338 Ansa (loop) cervicalis, 273, 287, 288, 390 subclavia, 365, 366 Anterior crural nerve. See NERVE. cutaneous nerves of abdomen, 310, 311, 381 thorax, 307, 308, 310, 381 interosseous artery, nerves of, 301 roots of spinal nerves, 276, 358, 359, 381, 384 thoracic nerves. See NERVES. tibial nerve, 335, 336, 337, 384 Antrum, maxillary, nerves of, 338 Anus, nerves to muscles of, 352 Aortic plexus, 370, 375, 376, 377 Aortico -renal ganglion, 369, 375 Arm, cutaneous nerves of, 343 nerves to muscles of, 353 Arnold, ganglion of. See GANGLION, OTIC. nerve of, 265 Arterk-s, nerves of, anterior interosseous, 301 brachial, 297 carotid, external, 364 internal, 362 central of retina, 362 cerebral, 362 femoral, 319 internal mammary, 366 ophthalmic, 362 palmar, 300 peroneal, 333 subclavian, 366 tibial, anterior, 332 posterior, 332 ulnar, 299 vertebral, 366 Articular nerves. See the several joints. Ascending branch of upper cervical ganglion, 361, 362, 366 branches of cervical plexus, 286 root of fifth nerve, 233 Astragalo-calcaneal joint, nerve of, 332 Astragalo-navicular joint, nerve of, 333 Atrial plexus, 373 Auditory meatus, external, nerves of, 246 nerve. See NERVE. Auricular nerves. See NERVES. Auriculo-temporal nerve. See NERVE. BACK, cutaneous nerves of, 341 motor nerves of, 352 Bladder, inhibitory nerves of, 370 motor nerves of, 370, 372 sensory nerves of, 350 Brachial artery, nerves of, 297 plexus, 283, 289, 307, 382, 383 Buccal nerves. See NERVES. Bulbar plexus of heart, 373 portion of spinal accessory nerve, 269, 270, 386, 388 root of fifth nerve, 233 Buttock, cutaneous nerves of, 344 CALCANEAL branches, 332, 333 Calcaneo-cuboid joint, nerve of, 334 Calcaneo-plantar nerve, 333 Cardiac nerves. See NERVES. plexus. See PLEXUS. Carotico-tyrnpanic nerve, 260, 262 Carotid artery, external, nerves of, 364 internal, nerves of, 362 branch of ninth nerve, 260 upper cervical ganglion, 362 plexus, 234, 243,250, 260, 362 Carpo-metacarpal joints, nerves of, 305 Cauda equina (horse's tail), 277 Cavernous nerves of penis, 378 plexus, 230, 233, 235, 238, 362 sinus, nerves in relation to, 231 Cavities cf head, nerves of, 338 Cavum (a hollow) Meckelii, 234 Central artery of retina, nerves of, 362 Cerebral arteries, nerves of, 362 Cerebro-spinal nerves, 221 muscular distribution of, 351 sensory distribution of, 338 Cervical branch of facial nerve, 256, 287 gangliated cord, 361 ganglion. See GANGLION. nerves. See NERVES. plexus, 283, 285 cutaneous area of, 341 posterior, 280 splanchnic nerves, 361 • sympathetic, 361 constitution of, 366 394 INDEX AND GLOSSARY TO VOLUME III., PAKT II. Cervico-cranial rami viscerales, 359 Cervico-facial division of facial nerve, 252, 255 Chest-wall, nerves to muscles of, 352 Chiasma. See COMMISSURE. Chorda tympani, 226, 247, 248, 249, 253, 256, 386, 387 SBi Ciliary ganglion. See GANGLION. nerves. See NERVES. Circulus tonsillaris, 261 Circumflex nerve, 291, 294, 383, 384 Clitoris, dorsal nerve of, 328, 330 Coccygeal ganglion, 371 nerves. See NERVES. plexus, 323 Cochlea, spiral ganglion of, 256 Cochlear nerve, 257, 258 Cceliac plexus, 376 Collateral digital nerves, 300, 302, 305, 333 ganglia, 357, 361 nerve, ulnar, 303, 304 Commissure, optic, 227, 228 Communicating nerve, fibular, 336 peroneal, 332, 336 tibial, 332 Cord, dorso-lumbar, 312, 315 gangliated. See SYMPATHETIC. lumbo-sacral, 313, 322, 323 Cords of brachial plexus, 289, 291, 383 Coronary nerves, 372, 373 plexus of heart, 372 of stomach, 376 Cranial cavity, sensory nerves of, 341 nerves. See NERVES. plexuses of sympathetic, 362 Crural nerve, anterior, 313, 317, 3 1 9, 383, 384 plexus, 383 Cutaneous area of cervical plexus, 341 of dorsal and first lumbar nerves, 341 distribution of nerves to trunk and limbs, 344 innervation of limb, rules of, 345 nerves. See NERVES. or perforating branches of segmental nerves, 381,382 Cystic plexus, 376 DENTAL nerves. See NERVES. plexus, inferior, 247 superior, 241 Depressor nerve, 268 Descending cervical nerve, 271, 273, 274, 283, 287, 288 root of fifth nerve, 233 Diaphragmatic ganglion, 375 nerve, 288 plexus, 375 Diazonal (5fa, through ; ((avi}, girdle) nerves, 383 Digastric branch of facial nerve, 254, 390 Digital nerves. See NERVES. Distribution of cranial nerves, 225, 338, 351 cutaneous, of nerves to trunk and limbs, 344 muscular, of cerebro-spmal nerves, 351 of spinal nerves, 354 sensory, of oerebro-spinal nerves, 338 visceral, of sensory spinal nerves, 350 Divisions, of nerves of limb-plexuses, 383 primary, of spinal nerves, anterior, or ven- tral, 283, 341, 381, 382 posterior, or dorsal, 278, 341, 38i Dorsal nerve of clitoris, 328, 330 Dorsal nerve of penis, 328, 329, 382 nerves. See NERVES. Dorso-lumbar cord or nerve, 312, 315 Dura mater, nerves of, 341 EFFERENT nerves. See NERVES. Eighth pair of cranial nerves. See NERVES. Elbow-joint, nerves of, 297, 299, 301, 303, 304, 307 Eleventh pair of cranial nerves. See NERVES. Eyelid, nerves of involuntary muscle of, 367 sensory nerves of, 338 Epididymis, sensory nerves of, 351 Epigastric or solar plexus, 373 Ethmoidal cells, nerves of, 338 nerve, posterior, 237 Eustachian tube, nerves of, 341 Exit of nerves from cranium, 223 FACE, motor nerves of, 351 pilo-motor nerves of, 367 sensory nerves of, 338 Facial nerve. See NERVE. Femoral artery, nerve of, 319 cutaneous branches of small sciatic, 328 nerve, 319 Femur, nerves of, 319, 321, 322 Fibres, sympathetic, 357, 358 Fibular branch of posterior tibial, 333 Fibular communicating nerve, 336 Fifth pair of cranial nerves. See NERVES. Fila radicularia, 275 Fingers, cutaneous nerves of, 343 First pair of cranial nerves. See NERVES. Foot, motor nerves of, 353 sensory nerves of, 344 Forearm, motor nerves of, 353 sensory nerves of, 343 Fossa, nasal, nerves of, 338 Fourth pair of cranial nerves. Sec NERVES. Frontal nerve, 231, 233, 235, 236 sinus, nerves of, 338 Funiculus solitarius, 258, 261, 386 Furcal (furca, fork) nerves, 313, 325, 383 GANGIJATED cord. See SYMPATHETIC. GANGLION or GANGLIA, aberrantia, 277 acoustic, 256, 387, 388 aortico-renal, 369, 375 of Arnold. See GANGLION, OTIC. cardiac, 373 cervical sympathetic, lower, 268, 283, 288, 365 middle, 283, 288, 365, 366 upper, 259, 264, 265, 272, 273, 283, 284, 361, 366, 367 cervicale uteri, 378 ciliary, 221, 228, 230, 236, 237, 241, 357, 359, 363, 387 coccygeal, 371 cceliac, 375 collateral, 357, 361 connected with cranial nerves, 387 diaphragmatic, 375 Gasserian, 225, 234, 246, 247, 362, 387 geniculate, 243, 252, 253, 258, 260, 365, 387» 388 geniculi, 252 of hypoglossal nerve, 274 INDEX AND GLOSSARY TO VOLUME III., PART II. 395 Ganglion or ganglia — continued. impar, 371 intervertebral, 275, 276, 277 jugular, 258, 259, 387 jugulare, 262 lateral, 357 of lateral root of auditory nerve, 256, 257 lenticular. See GANGLION, CILIARY. lingual. #«GANGLION, SUBM AXILLARY. of lingual branches of ninth nerve, 261 of lingual nerve, 248 of Meekel. See GANGLION, SPHENO- PALATINE. mesenteric, inferior, 370, 371, 376 superior, 375, 376 lumbar sympathetic, 370 nasal. See GANGLION, SPHENO-PALA- TINE. of nasal nerve, 237 nodosum, 262 ophthalmic. Sec GANGLION, CILIARY. otic, 221, 237, 244, 246, 248, 260, 357, 387, 388 petrosal, 258, 259, 387 of pharyngeal plexus, 265 phrenic, 288, 375 of posterior pulmonary plexus, 269 prevertebral, 357 radicis cochlearis, 256 renal, 375 of root of tenth nerve, 262, 264, 270, 36i, 387 sacral, sympathetic, 371, 377 semilunar, 367, 369, 375 semilunare, 234 spermatic, 375 spheno-palatine, 221, 237, 238, 239, 241, 357, 387, 388 spinal, 275, 276, 277, 384 of spinal-accessory nerve, 270 spiral of cochlea, 256, 258 splanchnic, 369 splanchnic or vagrant, 384, 387 stationary, 384, 387 stellate, 366, 369 sublingual, 248 submaxillary, 221, 237, 248, 357, 387, 388 superius of ninth rierve, 259 of suprarenal nerves, 375 sympathetic, 259, 264, 265, 268, 384, 387 temporal, 365 of tenth nerve, lower, 262, 264, 265, 272, 284, 361, 387 upper, 262, 264, 265, 270, 387 terminal, 357 of terminal branches of phrenic nerve, 288 thoracic, sympathetic, .365, 367 thyroid, 365 trunci sympathici, 358 of trunk of tenth nerve, 262, 264, 265, 272, 284, 361, 387 vertebra], 357 vestibular, 256, 257 vestigial, of facial nerve, 252, 387 of fifth nerve, 233, 387 of fourth nerve, 233, 387 of third nerve, 231, 387, 388 of Wilsberg, 372 Gasserian ganglion, 225, 234, 246, 247, 362, 387 Gastric nerves, 226, 263, 264, 269 plexus, 269 Gastro-epiploic plexus, 376 Geniculate ganglion. See GANGLION. Geniculum nervi facialis, 252 Genito-crural nerve, 313, 315, 370, 382 Genu (knee) inner, of facial nerve, 251 outer, of facial nerve, 252 Gland, tympanic, 260 Glosso-pharyngeal nerve. See NERVE. Gluteal nerves. See NERVES. Grey rami communicantes, 358, 359, 361, 365, 367, 384 Gudden, inferior commissure of, 228 H^MORRHOIDAL nerves. See NERVES. plexus, 377 Hand, cutaneous nerves of, 343 muscular nerves of, 353 joints of, nerves of, 301 Head, nerves to muscles of, 351 sensory nerves of, 338 vaso-motor nerves of, 367, 369 Heart, accelerator nerves of, 367, 369 inhibitory nerves of, 269, 270 sensory nerves of, 350 Hepatic plexus, 269, 288, 375, 376 Hip, nerves of muscles of, 353 Hip-joint, nerves of, 318, 319, 321, 322, 325 Homologies of limb nerves, 383 Humei us, nerves of, 297, 304 Hypogastric plexus, 361, 370, 372, 376, 377, 378 inferior, 377 Hypoglossal nerve. See NERVE. ILIO-HYPOGASTRIC nerve, 311, 312, 313, 314, 315 Ilio-inguinal nerve, 312, 313, 314, 315, 382 Incisor branches, 241, 247 Inferior maxillary nerve, 223, 234, 243, 248, 249 Infraclavicular branches of brachial plexus, 290, 291, 294 Infrahyoid muscles, nerves of, 351 Inframaxillary nerve, 256 Infraorbital branches of facial nerve, 255 nerve, 238, 240 plexus, 241 Infratrochlear nerve, 233, 236, 237, 255 Inguinal branch of ilio-hypogastric, 315 Inhibitory nerves of bladder, 370 of rectum, 370 Inneivation, cutaneous, of limbs, rules of, 345 Intercostal nerves, 288, 307, 308, 310, 345, 382, 383 Intercosto-humeral nerve, 296, 297, 308, 310, 384- Intermediate plexus, 373 Intermesenteric plexus, 376 Internal cutaneous nerve of arm, 291, 295, 299, 301, 384 small, 291, 295, 296 of thigh, 318, 319, 321, 322, 384 mammary artery, nerves of, 366 saphenous nerve, 318, 319, 320, 321, 384 Interosseous nerve, anterior, 301, 303, 307 posterior, 300, 303, 306, 384 Interphalangeal joints, nerves of, 302, 303, 305, 307, 334 Intervertebral ganglia, 275, 276, 277 396 INDEX AND GLOSSARY TO VOLUME 111., PART II. Intestines, sensory nerves of, 350 viscero-inhibitory nerves of, 369 Intumescentia ganglioformis Scarpse, 257 Iter chordae anterius, 254 posterius, 254 JACOBSON, nerve of, 260 Jugular ganglion, 258, 259, 387 KIDNEY, sensory nerves of, 350 vaso-niotor nerves of, 370 Knee-joint, nerves of, 318, 319, 321, 322, 331, 335. 336, 338 LABIAL nerves, 241, 247 Lachrymal nerve, 231, 235, 238, 240,254, 255 Laryngeal nerves. See NERVES. Larynx, motor nerves of, 352 sensory nerves of, 341 Last dorsal nerve. See TWELFTH DORSAL NERVE. Lateral cutaneous nerves. See NERVES. Lateral ganglia, 357 Leg, cutaneous nerves of, 344 muscular nerves of, 353 Lenticular ganglion. See GANGLION, CILIARY. Ligament, round of uterus, motor nerves of, 370 Limb, cutaneous innervation of, rules of, 345 lower, cutaneous nerves of, 344, 349, 382 muscular nerves of, 353, 354, 382 upper, cutaneous nerves of, 343, 344, 348, 382 muscular nerves of, 352, 354, 382 Limb-nerves, morphology of, 382 homologies of, 383 Limb-plexuses, divisions of nerves of, 383 Lingual branches of ninth nerve, 261 branch of vagus, 265, 272 ganglion. See GANGLION, SUBMAXILLARY. nerve, 243, 247, 261, 271, 272, 390 Lips, nerves of, 238, 241, 247, 338 Liver, sensory nerves of, 350 Long scrotal nerves, 329 Lower limb, cutaneous nerves of, 344, 349 muscular nerves of, 353, 354 Lumbar gangliated cord, 370 Lumbar nerves, 274, 281, 311, 355, 382 fifth, 322 plexus, 283, 311, 312, 383 sympathetic, constitution of, 370 ganglia, 370, 375, 377 Lumbo-sacral cord, 313, 322, 323 Lungs, sensory nerves of, 350 MALAR branches of facial nerve, 254 nerve, 239, 240, 255 Mandibular branch of facial nerve, 256 nerve, 247, 390 Masseteric nerve, 243, 244, 245 Mastoid branch of great auricular, 286 cells, nerves of, 341 Maxillary antrum, nerves of, 341 nerves. Sec NERVES. Meatus, external auditory, nerves of, 246 Meckel's ganglion. See GANGLION, SPHENO- PALATINE. Median nerve, 291, 299, 300, 301, 384 Meningeal branch of vagus, 265 or recurrent branches of spinal nerves, 278, 360, 381, 384 Mesenteric ganglia. See GANGLIA. plexus. See PLEXUS. Metacarpo-phalangeal joints, nerves of, 300, 302, 303, 305> 307 Metatarsal bones, nerves of, 338 Metatarso-phalangeal joints, nerves of, 335, 338 Metazonal (juerct, behind ; C*"*?* girdle) nerves, 383 Middle cutaneous nerve of thigh, 317, 319, 320, 322 Mononeural (^6vos, single ; vtvpov) muscles, 383 Morphology of cranial nerves, 385 of limb- nerves, 382 of peripheral nerves, 381 Motor nerves of bladder, 370, 372 of rectum, 370, 371 of round ligament of uterus, 370 of uterus, 370, 372 of vas deferens, 370 nuclei, 222, 386 root of ganglia, 237, 386 Mouth, sensory nerves of, 338 Muscular distribution of cerebro- spinal nerves, 35? of spinal nerves, 354 Musculo-cutaneous nerve of lower limb, 332. 335, 336, 384 of upper limb, 291, 297, 306 Musculo -spiral nerve, 291, 300, 303, 384 Mylo-hyoid nerve, 244, 247, 261 NASAL branch of superior maxillary nerve, 241 of spheuo-palatine ganglion, 242 of vidian nerve, 243 fossa, nerves of, 338 ganglion. See GANGLION, SPHENO-P ALA- TINE. nerve, 231, 233, 235, 236, 238, 255, 388, 390 Naso-ciliary nerve, 236 Naso- palatine nerve, 242 Naviculo-cuneiform joint, nerve of, 333 Neck, muscular nerves of, 351, 352 NERVE or NERVES (vevpov, originally sinew, tendon), 221 abdominal vaso-motor, 369, 370 abducent, 222, 223, 225, 231, 235, 238. 241, 250, 386, 388, 390 accelerator, of heart, 367, 369 afferent, of abdominal viscera, 370 alveolar, superior, 239, 240 inferior, 247 ampullary, 257, 258 of anconeus, 304, 307 anterior crural, 313, 317, 319, 383, 384 thoracic, external, 291, 293, 294, 384 internal, 291, 294, 384 of antrum, maxillary, 338 of Arnold, 265 articular. See the several joints, auditory, 222, 223, 224, 225, 252, 256, 286, 3.88 auricular, anterior, 246 great, 254, 256, 286 of great occipital, 280 posterior, 254, 265, 286 of small occipital. 286 INDEX AND GLOSSARY TO VOLUME III., PART II. 397 Nerve or nerves— continued. auricular, of vagus, 265, 386, 390 auriculo-temporal, 240, 243, 244, 246, 390 of bladder, inhibitory, 370 motor, 370, 372 sensory, 350 of brachial artery, 297 buccal, 240, 243, 246, 249, 256 of facial, 256 bucco-labial, inferior, 256 superior, 255 cardiac, deep, 365 of descending cervical nerve, 274 of external laryngeal, 265 great, 365 lower, 363, 365, 372 middle, 363, 365, 366, 372 of recurrent laryngeal, 268 upper or superficial, 268, 361, 363, 365, 372, 373 of vagus, 262, 265, 268, 372 calcaneo-plantar, 333 carotico-tympanic, 260, 362 cavernous, 378 cerebro-spinal, 221 muscular distribution of, 351 sensory distribution of, 338 cervical, 274, 276, 277, 280, 283, 354, 382 descending, 271, 273 first, 222,^278, 283 superficial, 256, 286 splanchnic, 361 chorda tympani, 226, 247, 248, 249, 253, 256, 386 ciliary, long, 236, 238, 366 short, 237, 238, 359 circumflex, 291, 294, 383, 384 coccygeal, 278, 283, 322, 371, 381 cochlear, 257, 258 of coraco-brachialis muscle, 297, 384 coronary, 372, 373 cranial, 221 constitution of, 385 distribution of, 225, 390 eighth pair. See Auditory. eleventh pair. See Spinal Acces- sory. exit of, from cranium, 223 fifth pair. See Trifacial. first pair. See Olfactory. fourth pair. See Trochlear. morphology of, 385 ninth pair. See Glosso - pharyn- geal. nuclei of, 222 number of, 221 origin of, deep, 222 superficial, 222. second pair. See Optic. seventh pair. See Facial. sixth pair. See Abducent. segmentation of, 388 Scemmering's enumeration, 221 tenth pair. See Pneumo-gastric. twelfth pair. See Hypoglossal. third pair. See Oculomotor. Willis's enumeration, 221 cutaneous, anterior, of abdomen, 310, 311 of thorax, 307, 308, 310 external, of upper limb, 297, 304 VOL. III., PT. 2. Nerve or nerves— continued. cutaneous, external, of lower limb, 313, 317, 382, 383, 384 of head, 338 internal, of anterior crural, 318, 319, 384 of musculo-spiral, 304, 310 small, 291, 295, 296, 384 of brachial plexus, 291, 295, 384 lateral, of abdomen, 310, 314, 381 of leg, 336 of thorax, 307, 308, 344, 381, 382 of lower limb, 344, 349, 382 middle, 317, 319 occasional, of obturator, 318, 320 perforating, 324, 325, 328, 382, 384 plantar, of posterior tibial, 333 of perineum, 343 of trunk, 341', 344, 350 of upper limb, 343, 344, 348, 382 cutaneous or perforating, of segmental nerves, 381, 382 dental, inferior, 243, 246, 247 lesser, 247 superior, 239, 240 depressor, 268 diaphragmatic, 288 diazonal, 383 digital of foot, 322, 332, 333, 334, 336, of hand, 300, 302, 303, 304, 305 dorsal, 274, 276, 277, 280, 283, 307, 344, 355. 36i, 366 of clitoris, 328, 330 first, 307 of penis, 328, 329 twelfth, 307, 311, 314, 315, 317, 322, 344, 382 of dorso-lateral muscle, 381 dorso- lumbar, 312 of epididymis, sensory, 351 of ethmoidal cells, 338 ethmoidal, posterior, 237 of external auditory meatus, 246 facial, 222, 224, 226, 236, 251, 262, 359, 386, 387, 388, 390 genu of, inner, 251 outer, 252 femoral, 319 fibular communicating, 336 frontal, 231, 233, 235, 236 of frontal sinus, 338 furcal, 313, 325, 383 gastric, 269 genito-crural, 313, 315, 370, 382 gluteal, inferior, 324, 325, 326, 331, 383, 384 superior^ 322, 324, 325, 383, 384 glosso-pharyngeal, 222, 223, 224, 225, 226, 254, 258, 359, 386, 387, 388, 390 haemorrhoidal, interior, 328, 329, 330, 382 superior, 377 of heart, 268, 269, 270, 350, 363, 365, 367, 369, 372 hypoglossal, 222, 223, 224, 225, 226, 248, 26$, 271, 385, 387, 388, 390 iho-hypogastric, 311, 312, 313, 314, 315 ilio-inguinal, 312, 313, 314, 315, 317, 382 inframaxillary, 256 infraorbital, 238, 240 infratrochlear, 233, 236, 237, 255, 390 c c • 398 INDEX AND GLOSSARY TO VOLUME III., PART II. Nerve or nerves — continued. inhibitory of heart, 269, 270 intercostal, 288, 307, 308, 382, 383 first, 307 lower or abdominal, 310 upper or pectoral, 308 intercosto-humeral, 296, 297, 308, 310, 384 interosseous, anterior, 301, 303, 307 posterior, 300, 303, 306, 384 of intestines, inhibitory, 369 motor, 269 sensory, 350 of Jacobson, 260 of joints. See the several joints. of kidney, sensory, 350 vaso-motor, 370 labial, 241, 247, 338 lachrymal, 231, 235, 238 laryngeal, external, 265, 268, 361, 363, 364, 365 inferior or recurrent, 264, 266, 268, 363, 365, 366, 390 internal, 265 middle, 266 superior, 262, 265, 268, 270, 363, 390 of levator ani, 323, 329 of limbs, homologies of, 383 morphology of, 382 of limb-plexuses, divisions of, 383 lingual, of fifth nerve, 243, 247, 261, 271, 272, 390 of glosso-pharyngeal, 261 of vagus, 265 of lips, 241, 247, 338 of liver, sensory, 350 long scrotal, 329 lumbar, 274, 281, 311, 344, 355, 382 fifth, 322 of lungs, sensory, 350 malar, 239, 240, 255 mandibular, 247, 390 masseteric, 243, 244, 245 maxillary, inferior, 223, 234, 243, 388, 39p superior, 223, 234, 238, 388, 390 median, 291, 299, 300, 301, 384 mental, 247, 256 met-azonal, 383 morphology of, 381 of muscles of head, 351, 390 of lower limb, 353, 354, 382 of neck, 351, 352, 390 of trunk, 352, 354 of upper limb, 352, 354, 382 musculo-cutaneousof arm, 291, 297,302, 384 of leg, 322, 332, 335, 336, 338, 384 musculo-spiral, 291, 300, 303 mylo-hyoid, 244, 247, 261 nasal, 231, 233, 235, 236, 238, 255, 388 of nasal fossa, 338 naso-ciliary, 236 naso-palatiue, 242 obturator, 313, 317, 320, 321, 383, 384 accessory, 317, 319, 322 of obturator interims, 324, 325, 384 occipital, great, 280, 286 small, 254, 280, 286 third, 280 oculomotor, 222, 223, 225, 228, 238. 359, 386, 387, 390 external. See Abducent, oculo-nasal, 236 Nerve or nerves — continued. olfactory, 222, 223, 225, 227, 385 ophthalmic, 223, 230, 231, 233, 234, 235, 250, 388 optic, 222, 223, 225, 227, 24T, 385 orbital, 239 of ovary, 351, 375, 378 palatine, external, 242 large or anterior, 242, 243 small or posterior, 242 parotid, 246, 249, 256, 261, 286 pathetic. See Trochlear. of pectineus muscle, 320, 384 pelvic splanchnic, 359, 371 of penis, 341, 343 vaso-constrictor, 370 vaso-dilator, 370, 372 perineal, 328 ^ deep, 329 superficial, 328, 329, 330 peroneal. See Popliteal, external. communicating, 332, 336 petrosal, external superficial, 253 large deep, 243, 253, 262 superficial, 243, 252, 256, 260, 362, 386 small deep, 260, 362 small superficial, 249, 253, 260, 261, 386, 388 pharyngeal, of glosso-pharyngeal, 260 of sympathetic, 363 of vagus, 265 phrenic, 274, 288, 385 accessory, 288 pilo-inotor, 359, 367, 369, 370, 371 plantar, external, 332, 334, 337, 384 internal, 332, 333, 33 j, 384 pneumo-gastric, 222, 223, 224, 226, 254, 259, 261, 270, 274, 359, 364, 386, 388, 390 popliteal, external, 324, 325, 328, 330, 332, 335' 383, 384 internal, 322. 324, 325, 328, 330, 331, 383, 384 postaxial of limb-borders, 349 posterior thoracic, 291, 293, 383 preaxial of limb-borders, 348, 349 pretracheal, 364 prezonal, 383 of prostate, secretory, 372 sensory, 351 pterygoid, external, 243, 246 internal, 244, 246, 248, 249 pudendal, interior, 326, 328, 329, 330 pudic, 324, 325, 328, 370, 378, 382 pulmonary, anterior, 268 pupillo-dilator, 366, 369 of pyriforrnis, 324, 325, 326, 383 of quadratus femoris, 324, 325, 384 radial, 297, 298, 300, 302, 303, 304, 384 of rectum, inhibitory, 370 motor, 370, 371 sensory, 350 recurrent articular, 336 of hypoglossal, 271 laryngeal. See Laryngeal, inferior. of maxillary, inferior, 244 superior, 239 of ophthalmic, 235 of spinal nerves, 278, 360, 381, 384 of vagus, 265 of rhomboid muscles. 292, 383 INDEX AND GLOSSARY TO VOLUME III., PART II. 399 Nerve or nerves — continued. of round ligament of uterus, motor, 370 saccular, 257, 258 sacral, 274, 276, 277, 278, 281, 322, 356, 38i fifth, 323, 381 fourth, 323, 381 sixth, 323 saphenous, external or short, 327, 331, 332, 336, 338 internal or long, 318, 319, 320, 321, 322, 336, 338, 384 sciatic, great, 324, 328, 330, 383 small, 324, 325, 326, 331, 336, 382, 383, 384 of scrotum, 341, 343 segmental, 344, 350, 354, 381, 382, 384, 385, 388 sensory, of cavities of head, 338 distribution of, 338 of head, 338 of viscera, 350 somatic afferent, 384, 388 efferent, mesial, 384, 385, 386, 388 lateral, 385, 386, 388 spheno-ethmoidal, 237 sphenoidal, 243, 249 of sphenoidal sinus, 338 spheno-palatine, 239, 241, 242, 243 spinal, 221, 274 connection of, with sympathetic cords, 283, 357, 358, 359,' 361 cutaneous distribution of, to trunk and limbs, 344 muscular distribution of, 354 roots of, 256 segmentation of, 381 sensory distribution of, to viscera, 350 spinal accessory, 222, 223, 224, 226, 262, 265, 269, 359, 385, 386, 388, 390 splanchnic afferent, 384, 388 efferent, 384, 386, 388 non-gangliated, 385 great, 367, 369, 375 small, 367, 369, 375 smallest, 367, 369, 375 of stomach and intestines, motor, 269 sensory, 350 viscero-mhibitory, 369 subcostal, 307 of submaxillary gland, secretory, 367, 369 suboccipital, 221, 222, 274, 277, 278, 283 subscapular, 291, 294, 383 long, 294 supraclavicular, 287, 310 supramaxillary, 256 supraorbital, 236, 254, 255, 390 suprascapular, 291, 293, 383 supratrochlear, 233, 236, 237 of sweat-glands, secretory, 369, 370 sympathetic, 221, 357, 372, 384 temporal, 235, 239, 254 deep, 243, 245, 246 superficial, 246 temporo-malar, 239, 390 thoracic. See also Dorsal. anterior internal, 291, 294, 384 external, 291, 293, 294, 384 of testis, sensory, 351 tibia), anterior, 335, 336, 337, 384 communicating, 332 posterior. 331, 332, 384 Xerve or nerves — continued. of tongue, sensory, 248, 256, 261, 338 muscular, 351, 390 trifacial, or trigeminal, 222, 223, 225, 233, 386, 387, 388 trochlear, 222, 223, 225, 231, 235, 238, 386, 387, 388, 390 of trunk and limbs, cutaneous distribution of, 344 tympanic, 259, 260, 362 ulnar, 291, 295, 296, 299, 302, 303, 306, 384 collateral, 303, 304 of ureter, sensory, 350 of uterus, 351, 370, 372, 375, 378 motor, 370, 372 and appendages, sensory, 351 utricular, 257, 258 vaginal, 378 of vas deferens, 370, 377 vaso-constrictor, 359 of limbs, 369, 370, 371 pulmonary, 369 vaso-dilator, 359 vaso- motor, 359, 367, 369 of ventro-lateral muscle, 381 of vesicula seminalis, 377 vestibular, 257, 258 vidian, 243, 249, "253, 362 viscero-coristrictor, 359 viscero-inhibitory, 359 of Wrisberg, 291, 296, 384 Nerve-plexuses. !See PLEXUS. Nerve-roots. See ROOTS. NERVUS vel NERVI, acusticus, 256 alveolaris, inferior, 247 ano-coccygei, 323 axillaris, 294 carotici externi, 364 caroticus internus, 362 cerebrales, 221 clunium inferiores, 327 medii, 281 superiores, 281 cutaneus antibrachii dorsalis, 304 medialis, 295 brachii medialis, 296 lateralis, 295 posterior, 304 femoris lateralis, 317 posterior, 326 sura? lateralis, 336 medialis, 332 dorsalis scapulas, 292 erigentes, 372 furcalis, 313, 325, 383 genito-femoralis, 315 hsemorrhoidales medii, 323 intercosto-brachialis, 310 intermedius, 251 ischiadicus, 330 jugularis, 361 labiales posteriores, 329 lumbo-inguinalis, 316 mandibularis, 243 masticatorius, 243 maxillaris, 238 meningeus medius, 239 perforans coccygeus major, 328 peronaeus communis, 335 profundus, 337 superficialis, 336 400 INDEX AND GLOSSARY TO VOLUME III., PART II. Nervus vel nervi — continued. pudenclus, 328 radialis, 303 renalis posterior, 369 scrotales posteriores, 329 spermaticus extermis, 316 spinosus, 244 splanchnicus supremus, 369 subcutaneus colli, 286 suralis, 332 tentorii, 235 thoracalis longus, 293 thoraco-dorsalis, 294 tibialis, 331 vaginales, 323 vagus, 261 vesicales inferiores, 323 vestibuli, 257 zygomaticus, 239 Ninth pair of cranial nerves. See NERVES. Nuclei of nerves, motor, 222, 386 sensory, 222, 386 OBTURATOR nerve, 313, 317, 320, 322, 383, 384 accessory, 317, 319, 322 Occasional cutaneous branch of obturator,3 18.320 Occipital nerve, great, 280, 286 of posterior auricular, 254 small, 254, 280, 286 third, 280 Occipito-atlantal joint, nerve of, 284 Oculomotor nerve. See NERVE. Oculo-nasal nerve, 236 (Esophageal branches, 268, 269 plexus, 262, 264, 269 (Esophagus, motor nerves of, 269 sensory nerves of, 341 Olfactory nerves, 222, 223, 225, 227, 385 Ophthalmic artery, nerves of, 362 Ophthalmic ganglion. See GANGLION, CILIARY. Ophthalmic nerve, 223, 230, 231, 233, 234, 235, 250, 388 Optic commissure, 227, 228 nerves, 222, 223, 225, 227, 241, 385 tracts, 227 Orbit, nerves to muscles of, 351 Orbital nerve, 239 Origin, deep, of cranial nerves, 222 superficial, of cranial nerves. 222 Os uteri, sensory nerves of, 351 Otic ganglion. See GANGLION. Ovary, nerves of, 351, 375, 378 PACINIAN bodies, 301, 302, 332, 333, 334, 377 Palate, soft, motor nerves of, 352 sensory nerves of, 339 ' Palatine nerves. See NERVES. Palm, cutaneous nerves of, 343 Palmar arteries, nerves of, 300 branch of uinar nerve, deep, 300 superficial, 300 cutaneous branch of median nerve, 302 ulnar nerve, 299, 302 Palpebral nerves, 235, 236, 237, 241, 255 Pancreatic plexus, 376 Pancreatico-duodenal plexus, 376 Par (pair) vagum (wandering), 261 Parotid nerves, 246, 249, 256, 261, 286 Pars intermedia of Wrisberg, 251, 252, 254, 258, Patellar branch of internal saphenous, 322 plexus, 317, 322 Pathetic nerve. See NERVE, TROCHLEAR. Pectoral intercostal nerves, 308 Pelvic plexus, 370, 371, 372, 377 splanchnic nerves, 359, 371 Penis, nerves of, 341, 343 cavernous, 378 dorsal, 328, 329 motor, 352 vaso-dilator, 370 372 vaso-constrictor, 370 Perforating branches of external plantar nerve, cutaneous nerve, 324, 325, 328, 382, 384 or cutaneous branches of segmental nerves, 381, 382 Pericardial branches of vagus, 269 I Perineal branch of fourth sacral, 323, 382 nerve, 328 deep, 329 superficial, 328, 329, 330 Perineum, cutaneous nerves of, 343 Peripheral nerves, morphology of, 381 Peroneal artery, nerves of, 333 nerve, 324, 325 communicating, 332, 336 Pes anserinus (goose's foot), 252 Petrosal ganglion, 258, 259, 260, 262, 265, 361, 387 nerves. See NERVES. Pharyngeal branches of upper cervical ganglion, 36i, 363 of vagus, 261, 265, 270 division of ninth nerve, 260 nerves, 243, 260, 261, 262, 266, 268 plexus, 261, 265, 266, 363 Pharynx, motor nerves of, 352 sensory nerves of, 339 Phrenic ganglion, 288, 375 nerve, 274, 288, 291, 293, 366, 375, 385 accessory, 288 plexus, 375 Pilo-motor nerves, 359, 367, 369, 370, 371 Pituitary body, nerves of, 363 Plantar nerves. See NERVES. PLEXUS (plaiting, twining) or PLEXUSES, nervous 221, 383 aortic, 370, 375, 376, 377 aorticus abdominalis, 376 thoracalis, 367 atrial, 373 beneath sartorius muscle, 318, 322 brachial, 283, 289, 307, 382, 383 bulbar, 373 cardiac, deep, 268, 363, 365, 366, 372, 373 superficial, 268, 363, 372, 373 caroticus externus, 364 internus, 362 carotid, 234, 243, 250, 260, 362 cavernous, 230, 233, 235, 238, 362 cervical, 283, 285 cutaneous area of, 341 posterior, 280 coccygeal, 323 co?liac, 376 co3liacus, 373 coronary of heart, 372 of stomach, 376 cranial, 362 cystic, 376 dental, inferior, 247 INDEX AND GLOSSARY TO VOLUME III., PART II. 401 Plexus or plexuses — continued. dental, superior, 241 diaphragmatic, 375 epigastric, 373 facial, 248 gastric, 269 gastro-epiploic, 376 great, of sympathetic, 372 hepatic, 269, 288, 375, 376 heemorrhoidal, 377 hypogastric, 361, 370, 372, 376, 377, 378 inferior, 377 infraorbital, 241 of intercostal nerves, 310, 383 intermediate, 373 intermesenteric, 376 ischiadicus, 324 linealis, 376 lumbar, 283, 311, 312, 317, 318, 383 mesenteric, inferior, 376 superior, 376. 377 middle meningeal, 249, 253 O3sophageal, 262, 264. 269 pancreatic, 376 pancreatico-duodenal, 376 parotideus, 252 patellar, 317, 322 pelvic, 370, 371, 372, 377 pharyngeal, 261, 265. 266, 363 phrenic, 375 prevertebral, 357, 359, 360, 361 prostatic, 378 pudendus, 324 pudic, 324 pulmonary, anterior, 268, 269, 364, 372 posterior, 262, 264, 268, 269, 367 pyloric, 376 renal, 269, ,367, 369, 370, 375 sacral, 283, 3", 3 12, 31 3, 322,323, 33O> 383 sciatic, 324 solar, 263, 269, 288, 361, 369, 372, 373 spermatic, 375, 376, 377 splenic, 269, 376 subclavius, 366 suprarenal, 375 tympanic, 260, 362 vertebralis, 366 vesical, 377 Pneumo-gastric nerve. See NERVE. Polyneural (TTO\US, many ; vtvpov] muscles, 383 Popliteal nerves. See NERVES. Portio dura (hard, tough), 222 intermedia, of Wrisberg, 251, 252, 254, 258, 386, 388 mollis (soft), 222 Postaxial limb- borders, nervos of, 349 Posterior auricular nerve, 254, 265, 286 interosseous nerve, 300, 306, 384 roots of auditory nerve, 256 of spinal nerves, 275, 276, 358, 359, 381, 384 thoracic nerve, 291, 293, 383 tibial nerve, 331, 332, 384 Postfixed type of lumbar plexus, 313 Preaxial limb-borders, nerves of, 348, 349 Prefixed type of lumbar plexus, 313 Pretracheal nerve, 364 Prevertebral ganglia, 357 plexuses, 357, 359, 360, 361 Prezonal nerves, 383 Primary divisions of spinal nerves, posterior or dorsal, 275, 278, 341, 381 Primary divisions of spinal nerves, anterior or ventral, 275, 278, 283, 341, 381, 382 Prostate, secretory nerves of, 372 sensory nerves of, 351 Prostatic plexus, 378 Pterygoid nerve. See NERVK. Pterygo-sphenoidal ligament, 244 accessory, 247 Pudendal nerve, inferior, 326, 328, 329, 330 Pudic nerve, 324, 325, 328, 370, 378, 382 Pulmonary nerves, anterior, 268 plexus. See PLEXUS. Pupillo-dilator fibres, 366, 369 Pyloric plexus, 376 QUABRATUS femoris muscle, nerve of, 324, 325, 384 RADIAL nerve, 297, 298, 300, 302, 303, 304, 384 Radius, nerve of, 301 Radix cochlearis, 256 vestibularis, 256 Ramus vel Rami, communicantes, grey, 358, 359,361,365,367,384 white,357,358, 367,371, 384 cutaneus anterior, 315 lateralis, 315 descendens hypoglossi, 273 efferentes, 357, 358, 360 ophthalmicus profundus, 388 perineales, 328 profundus nervi radialis, 306 superficialis nervi radialis, 304 viscerales, cervico-cranial, 359 visceralis, 381 zygomaticofacialis, 240 zygomaticotemporalis, 239 Rectum, inhibitory nerves of, 370 motor nerves of, 370, 371 sensory nerves of, 350 Recurrent nerves. See NERVES. Renal ganglia, 375 plexus, 269, 367, 369, 370, 375 Rhomboid muscles, nerve of, 292, 383 Ribs, nerves of, 308 ROOT or ROOTS, ascending or bulbar of fifth nerve, 233 of auditory nerve, 256, 257 of ciliary ganglion, 230, 236, 237, 238, 359, 363 descending or mesencephalic, of fifth nerve, 233 of ganglia, 237 of hypoglossal nerve, 271, 274 motor of fifth nerve, 225, 233, 243, 247 of otic ganglion, 249 sensory, of fifth nerve, 225 of spinal nerves, anterior, 275, 276, 354, 358, 359, 384 posterior, 256, 275, 358, 359, 381, 384 of spheno-palatine ganglion, 243 of submaxillary ganglion, 248, 365 of tenth nerve, 261 Round ligament of uterus, motor nerves of, 370 Rules of cutaneous nerve-supply of limbs, 345 SACCULAR nerve, 257, 258 Sacral nerves, 274,276,277,278,281,322,356,381 fifth, 323, 381 402 INDEX AND GLOSSARY TO VOLUME III., PART II. Sacral nerves — continued. fourth, 323, 381 sixth, 323 gangliated cord, 370 plexus, 283, 311, 312, 313, 322, 323, 330, 383 sympathetic, constitution of, 371 Sacro-iliac joint, nerves of, 281 Saphenous nerves. See NEKVES. Scapula, nerves of, 293 Sciatic nerves. See NERVES. plexus, 324 Scrotal nerves, long, 329 Scrotum, nerves of, 341, 343 Second pair of cranial nerves. See NEUYES. Secretory nerves of prostate, 372 of submaxillary gland, 367, 369 of sweat-glands, 369, 370 Segmental nerves, 344, 350, 354. 381, 382, 384, 385 Segmentation of cranial nerves, 388 of spinal nerves, 381 Semilunar ganglion, 367, 369, 375 Sensory distribution of cerebro-spinal nerves, 344 of spinal nerves to viscera, 350 fibres, spinal, to sympathetic system, 359 nerves. See NERVES. nuclei, 222 root of ciliary ganglion, 236, 237, 238 of fifth nerve, 225, 233 of ganglia, 237 of otic ganglion, 249 of spheno-maxillary ganglion, 243 of submaxillary ganglion, 248 zones of trunk and limbs, 344 Septal branch of nasal nerve, 237 Seventh pair of cranial nerves. See NERVES. Shoulder, cutaneous nerves of, 343 motor nerves of, 352 Shoulder-joint, nerves of, 293, 294, 295 Sinus, frontal, nerves of, 338 sphenoidal, nerves of, 338 Sixth pair of cranial nerves. See X Kit YE. Sixth sacral nerve, 323, 381 Soemmering's classification of nerves, 221 Soft palate, motor nerves of, 352 sensory nerves of, 339 Solar plexus, 263, 269, 288, 361, 369, 372, 373 Sole, cutaneous nerves of, 344 Somatic (o-oj/ia, body) afferent nerves, 384, 388 division of spinal nerves, 381 efferent, mesial, 384, 385, 386, 388 lateral, 385, 386, 388 Spermatic ganglion, 375 plexus, 375, 376, 377 Spheno-ethmoidal nerve, 237 Sphenoidal nerve, 243, 249 Sphenoidal sinus, nerves of, 338 Spheno-palatine ganglion, 221, 237, 238, 239, 241, 253, 256, 357, 387, 388 nerve, 239, 241, 242, 243 Spinal accessory nerve. See NERVE. cord, 223/274, 275 ganglia, 275, 276, 277, 384 nerves, 221, 274 connection with sympathetic cords, 357,358, 359, 361, 365, 367, 370, 37i cutaneous distribution of to trunk and limbs, 344 morphology of, 381 muscular distribution of, 354 Spinal nerves, primary division of, anterior, 275. 278, 283, 341, 381, 382 primary division of, posterior, 275, 278, 341, 381 roots of, 256, 275, 351, 359, 381 segmentation of, 381 sensory distribution, to viscera, 350 portion of spinal accessory nerve, 269, 270, 271, 385, 386, 390 Spiral ganglion of cochlea, 256, 258 Splanchnic ganglion, 369 nerves. See NERVES. Splanchnic ((nr\dyxva, viscera), or vagrant ganglia, 384 or visceral divisions of spinal nerves, 381 Splanchnics, abdominal, 367 cervical, 361 pelvic, 359, 371 Splenic plexus, 269, 376 Stapedius branch of facial, 253, 390 Stationary ganglia, 384, 387 Stellate ganglion, 366, 369 Sternal branches of intercostal nerves, 308 Sterno-clavicular joint, nerves of, 287 Sternum, nerves of, 308 Stomach, motor nerves of, 269 sensory nerves of, 350 viscero-inhibitory nerves of, 369 Striae medullares, 256, 257 1 Stylo-hyoid branch of facial, 254, 365, 390 Stylo-pharyngeus, nerve to, 261, 390 Subclavian artery, nerves of, 366 Subclavius muscle, nerve of, 288, 291, 293, 384 Subcostal nerve, 307 branches of intercostal nerves, 308 Sublingual ganglion, 248 Submaxillary ganglion, 221, 237, 248, 254, 256, 357, 365, 387, 388 gland, secretory nerves of, 367, 369 | Suboccipital nerve, 221, 222, 274, 277, 278, 283 Subscapular nerves, 291, 294, 383 Superficial cardiac nerve, 268, 361, 363, 365, 372, 373 cervical nerve, 256, 286 Superior maxillary nerve, 223,234,238,388,390 Supra-acromial branch of cervical plexus, 287 Supraclavicular nerves, 287, 310 Suprahyoid muscles, nerves of, 351 Supramaxillary nerve, 256 Supraorbital nerve, 236, 254, 255 Suprarenal plexus, 375 Suprascapular nerve, 291, 293, 383 Snprasternal branches of cervical plexus, 287 Supratrochlear nerve, 233, 236, 237 Sweat-glands, secretory nerves of, 369, 370 Sympathetic branch of spinal nerves, 381, 384 Sympathetic, cervical, constitution of, 366 fibres, 358 ganglia. See GANGLIA. lumbar, constitution of, 370 nerves, 221, 357, 372, 384 plexuses, great, 372 roots of ganglia, 237. 238, 243, 248, 249, 363, 365 sacral, constitution of, 371 thoracic, constitution of, 369 Synopsis of muscular distribution of nerves, 351 of sensory distribution of nerves, 338 TABLE of homologies of limb-nerves, 383 of muscular distribution of spinal nerves. 354 INDEX AND GLOSSARY TO VOLUME III., PART II. 403 Table of origins of brandies of brachial plexus, 291 of segmental nerves of head, 389 Tarsal joints, nerves of, 337 Tarso-metatarsal joints, nerves of, 335, 338 Temporal branches of facial, 254 ganglion, 365 nerve, 235, 239, 254 deep, 243, 245, 246 superficial, 246 Temporo-facial division of facial, 252, 254, 256 Temporo-malar nerve, 239 Temporo- maxillary joint, nerves of, 246 Tenth pair of cranial nerves. Sec NKRVKS. Terminal ganglia, 357 Testis, sensory nerves of, 351 Thenar eminence, cutaneous nerves of, 344 Thigh, nerves of, cutaneous, 344 muscular, 353 Third occipital nerve, 280 Third pair of cranial nerves. See NERVE. Thoracic ganglia, sympathetic, 365, 367 gangliated cord, 367 nerves. See NERVES. spinal, 274, 307 sympathetic, constitution of, 369 Thumb-muscles, nerves of, 302 Thyroid branches of middle cervical ganglion, 365 ganglion, 365 Tibia, nerves of, 331, 332, 336 Tibial artery, anterior, nerves of, 332 posterior, nerves of, 33.^ Tibial nerve. See NERVE. Tibial communicating nerve, 322 Tibio-fibular joints, nerves of, 331, 332, 336 Toes, articular nerves of, 334 cutaneous nerves of, 344 Tongue, muscular nerves of, 351, 390 sensory nerves of, 248, 256, 261, 338 Tonsillitic branches of ninth nerve, 261 Trachea, sensory nerves of, 341 Tracts, optic, 227 Trifacial or Trigeminal nerve. See NERVE. Trochlear nerve. See NERVE. Trunct sympathici, 358 Trunk, cutaneous nerves of, 341, 344, 350 muscular nerves of, 352, 354 Trunk-ganglion of vagus, 262, 264, 265, 272, 284, 361 Trunks of brachial plexus, 289 Tube, Eustachian, nerves of, 341 Twelfth dorsal nerve, 307, 311, 314, 315, 317, 322, 344, 382 Twelfth pair of cranial nerves. See NERVES. Tympanic branches, 246, 260 cavity, sensory nerves of, 341 gland, 260 membrane, nerves of, 341 nerve, 259, 260, 362 plexus, 260, 362 Types of lumbar plexus, 313 ULNA, nerve of, 301 Dinar artery, nerves of, 299 nerve, 291, 295, 296, 299, 302, 303, 306, 384 collateral, 303, 304 Ureter, sensory nerves of, 350 Urethra, muscular nerves of, 352 Uterine appendages, sensory nerves of, 351 Uterus, nerves of, 351, 370, 372, 375, 378 Utricular nerve, 257, 258 VAGAL portion of spinal accessory nerve, 270 Vaginal nerves, 378 Vagrant ganglia, 384, 387 Vagus nerve. See NERVE, PNEUMO- GASTRIC. Vas deferens, nerves of, 370, 377 Vascular branches of hypoglossal nerve, 272 of musculo-cutaneous nerve, 297 Vaso-constrictor nerves, cerebro-spinal, to sym- pathetic system, 359 of limbs, 369, 370, 371 of penis, 370 pulmonary, 369 Vaso-dilator nerves, cerebro-spinal, to sympathe- tic system, 359 of penis, 370, 372 Vaso-motor nerves, 359 abdominal, 369, 370 of head, 367, 369 of kidney, 370 Ventral or anterior primary divisions of spinal nerves, 283, 341, 381, 384 Vertebral artery, nerve of, 366 Vertebral ganglia, 357 Vesical plexus, 377 Vesicula -seminalis, nerves of, 377 "Vestibular ganglion, 256, 257 nerve, 257, 258 Vestigial ganglia of cranial nerves, 231, 235,252, 387, 388 \ridian nerve, 243, 249, 253, 362 Viscera, abdominal, afferent nerves of, 370 sensory distribution of spinal nerves to, 350 Visceral branches of fourth sacral nerve, 323 of sacral nerves, 371 or splanchnic division of spinal nerves, 3»i, 384 Viscero-constrictor nerves, cerebro-spinal, to sympathetic system, 359 Viscero-inhibitory nerves, cerebro-spinal, to sympathetic system, 359 of stomach and intestine, 369 WHITE rarni communicantes, 357, 358, 367, 371. 384 Willis's classification of cranial nerves, 221 Wrisberg, ganglion of, 372 nerve of, 291, 296, 384 pars intermedia of, 251, 252, 254, 258 Wrist-joint, nerves of, 300, 301, 303, 307 ZONES, sensory, of trunk and limb.-, 344 END OF PART II. 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