brain and spinal cord retain the medullary sheath, but want the primitive membrane. The sympa thetic fibres are often called gray or non-medullated; the others, white or medullated. The nerve-fibres in the limbs are about th of an

Fig. 4.

inch in diameter; in the brain they may be nearly ten times finer.

Nerve cells vary in size and form. Some are bipolar, others multipolar (fig. 5, A and C). Many, especially in the cortex of the brain, are pyramidal in shape (fig. 5, B), with fine processes, termed dendrons, coming off at various points and breaking up immediately into smaller branches ending in fine twigs, and one special branch which becomes the axis cylinder process of the nerve fibre, termed briefly

Fig. 5.-Nerve-cells:

A, from sympathetic ganglion; B, from cerebrum; C, from spinal cord; a.p., axis cylinder process.

the axon.

The term neurone is applied to the complete nerve unit, i.e. the body of the cell and all its branches. Impulses reach a nerve-cell by the dendrons and pass out by the axon. Each neurone is anatomically independent of every other neurone ; there is no true anastomosis of the branches from one nerve-cell with those from another, the arborisations interlace and intermingle, and nerve impulses are transmitted from one nerve unit to another through contiguous, but not through continuous, structures. This intermingling of arborisations is termed a synapse.

Fig. 6.

The various end-organs are described under the special sections. Fig. 6 shows the manner in which the fibres of a nerve end in a muscle.

The nerves arising from the brain are arranged

in twelve pairs. The first, or olfactory, is the nerve of smell. The second, or optic, is the nerve of sight. It arises from the retina, meets with its fellow in the optic chiasma, and is distributed half to each side of the brain, terminating partly in the corpora quadrigemina (for the reflex movements of the eye), and partly in the optic thalamus, passing thence to the occipital lobe of the cerebrum (for the sense of sight). The third or oculo-motor nerve arises under the corpora quadrigemina, and passes to all the muscles of the eye except two, which are supplied by the fourth and sixth pairs. The fourth nerve, arising immediately behind the third nerve, supplies the superior oblique muscle of the eye; while the sixth pair, arising from a nucleus near the middle of the floor of the fourth ventricle, supplies the external rectus muscle of the eye. The fifth pair has a very long origin from a point at the level of the third nerve down to the upper part of the spinal cord. It is the motor nerve to the muscles of mastication, and the sensory nerve to the face, front of the head, teeth, tongue, and is the nerve of taste of the anterior part of the tongue. It is this nerve which is concerned in neuralgia of the head and face and teeth. The seventh pair arises from the lower part of the pons Varolii (see BRAIN), and is the motor nerve to the facial muscles of expression. Injury to or disease of this nerve causes facial palsy, or Bell's paralysis. The eighth pair, or auditory nerve, supplies the internal ear. It is divided into two parts, one of which supplies the cochlea, and is the nerve of hearing proper, while the other supplies the semicircular canals, and is concerned in the maintenance of the equilibrium of the body. The nerve arises from the lateral and posterior part of the pons Varolii and medulla oblongata. The ninth pair, or glosso-pharyngeal nerve, is the special nerve of taste, and supplies the hinder third of the tongue, with the taste bulbs of which it is connected. The tenth pair, or pneumogastric nerve, has a very wide area of distribution to the lungs, heart, stomach, &c.; it is partly motor and partly sensory in function. The eleventh pair, or spinal accessory nerve, is the motor nerve to the larynx, and to certain muscles in the upper part of the neck. These three nerves arise from a groove in the side of the medulla oblongata and upper part of the spinal cord. The twelfth pair, or hypoglossal nerve, is the motor nerve of the tongue. Its origin is near the floor of the fourth ventricle, close to the middle line, and it emerges from the anterior surface of the medulla oblongata in a shallow groove between the anterior pyramids and the inferior olivary body (see BRAIN).

The spinal nerves arise from the spinal cord in pairs, thirty-one in number, and are named according to their relation to the vertebræ-cervical, dorsal, lumbar, and sacral. Their mode of origin will be understood from fig. 7, which represents diagrammatically the first part of their course, and on one side their relations with the sympathetic system-C 1-8 represents the eight pairs of cervical nerves; D 1-12, the twelve dorsal pairs; L 1-5, the five lumbar pairs; S 1-6, the five sacral pairs and the coccygeal pair. Each spinal nerve arises by two roots, an anterior aud a posterior (fig. 8, a and p; see also SPINAL CORD). These roots pass outwards, and unite before they leave the spinal canal. Before their union a small oval swelling is found on the posterior root, and is called its ganglion, g. The united nerve leaves the spinal canal by a small aperture between adjacent vertebræ. almost immediately gives off a fine medullated nerve to its corresponding sympathetic ganglion, a branch which can be traced into one of the internal organs. It also receives from the ganglion a nonmedullated or gray fibre, which is distributed to

It

the muscular coat of the blood-vessels, especially the arteries. The nerve thus altered passes outwards, dividing as it goes to send its ultimate branches into the fibres of the muscles, into the cells of the skin and connective tissues, tendons, and bones. In the dorsal region each nerve passes to its distribution without entering into connection with its neighbours, but in the cervical, lumbar, and sacral regions the nerves split up and form new junctions with each other, or plexuses as they are called. (These are indicated in fig. 1, and on the right-hand side of fig. 7, but the detailed description of them is impossible within the limits of this article.)

Functions of the Spinal Nerves. -Sir Charles Bell discovered that division of the anterior roots was followed by loss of power of voluntary motion, and that division of the posterior roots destroyed the power of sensation. He termed the anterior root motor, and the posterior sensory. It has since been ascertained that the anterior roots carry outwards other impulses that do not result in motion, and that the posterior roots carry inwards impulses which may not result in sensation. Therefore, it is more correct to term these roots respectively efferent and afferent. If the anterior root be divided between the point of its origin from the cells of the anterior horn of the spinal cord and its junction with the posterior root, the part unconnected with the cord will waste along the whole length of the nerve, and the muscles which it supplies will waste also. The cells in connection with the anterior roots, therefore, not only send out motor impulses, but exert a nutritive or trophic influence on the nerve and muscle. Division of the posterior root beyond its ganglion is followed by wasting of the corresponding fibres of the nerve to their ultimate termination. If the root be cut between the ganglion and the spinal cord, the part attached to

Fig. 7.

a

Fig. 8.

the ganglion remains unaltered, while that connected with the spinal cord wastes. This shows that the ganglion of the posterior root exerts a trophic influence on the fibres connected with it. If the nerve be divided after the junction of the two roots, the whole of the nerve farthest from the spinal cord will waste.

The afferent nerve impulses which pass along the posterior roots comprise those which give rise to the sense of touch, pain, and temperature, and to reflex movements of various kinds without necessarily exciting our consciousness, such as those concerned with the maintenance of the equilibrium

447

of the body, and with the functions of the internal

organs.

M

BRAIN

P.G.C.

Reflex Action.-The function of the nervous system is to bring any part of the organism into relation with any other part without the necessity of direct nervous connections from every part to every other part. It is like a telephone exchange where each subscriber has a central terminal which can be put into connection with that of any other subscriber. The nervous system, however, is more efficient, as the channels which bring in messages from different parts of the body (afferent fibres from sense organs) are different from the fibres (efferent) which convey A.C.C. messages outwards to organs which perform some action in response. The simplest mechanism consists of a sensory or receptive neurone and a motor neurone. This is Fig. 9. a reflex arc in which a sensory impression gives A, sensory neurone; a, sensory rise to a motor response. It is the functional unit of the nervous system, as the neurone is the anatomical unit. As the organism increased in complexity, a third or association neurone arose which connected the neurones of one segment with those of another segment. The progress of the nervous centres in complexity and efficiency depends essentially on the formation of longer and longer association neurones which extend farther and farther from the original reflex arc, and thus the most highly developed part of the nervous system, the cerebral cortex, consists largely in man of association neurones.

S

spinal connection; b, sensory pathway to brain; B, association neurone; C, motor neurone; c, motor fibre from brain; M, muscle; S, sensory endorgan; A.C.C., anterior cornua cell (motor); P.G.C., posterior ganglion cell (sensory); S-A-b, sensory connection with brain; c-B-C, motor pathway from brain; S-A-a-B-c, reflex arc.

A reflex arc usually consists of at least three neurones, a sensory, an association, and a motor (fig. 9). The simplest reflexes take place in the spinal cord, but the more highly complicated and specialised reflexes are carried out through the brain, which exerts a controlling influence upon all reflex response, inhibiting, exciting, changing excitation to inhibition, or vice versa as required, and thus constituting voluntary or volitional action. It is possible to explain the whole action of the nervous system as the result of the integration, co-ordination, interaction, combination, and adjustment of reflex activity.

It

The sympathetic nervous system, in contrast to the cerebro-spinal system which is under the control of the will, supplies those organs whose functions are not under voluntary control. innervates the heart-muscle, the plain muscle in the walls of the blood-vessels, and in the walls of the other contractile viscera, such as the stomach, intestine, bladder, and reproductive organs, and supplies secretory fibres to the glands. It is not an independent nervous system, but an outflow from the cerebro-spinal, and is distinguished by its connections with neurones lying outside the latter, together with its formation of peripheral plexuses at the places of its distribution. It is entirely efferent. Its overflow from the central nervous system occurs at four regions, the mid-brain, the medulla oblongata, the dorsal and the sacral regions of the spinal cord. The cells of origin in the spinal cord are situated in the lateral horn of gray matter, and are known as the intermedio-lateral

NESLE

fibres which quickens its action, and by an inhibitory group which slows it; the blood-vessels are supplied by vaso-constrictor and vaso-dilator fibres, &c. The characteristic quality of the innervation of all these tissues is due to the fact that their functions are able to continue independently of the nervous system, although influenced by it. Although the sympathetic and parasympathetic systems act separately from each other, and may be influenced independently by physiological stimu. lation and by drugs, and although their actions are antagonistic, it is possible they may both be controlled from some common centre. A disturb ance of their normal balance, however, may lead to the ascendency of either system, and a condition of hypertonus, either vagal or sympathetic, may result with characteristic symptoms of illness.

See Quain's Anatomy, vol. iii.; Sherrington, Integrative Action of Nervous System; Gaskell, Involuntary Nervous System; Keith Lucas, Conduction of Nervous Impulse; Schäfer, Text-book of Physiology.

Nesle, TOUR DE. The ancient castle of the noble family of Nesle stood, with its gate and tower, at an angle of the city wall of Paris, on the south bank of the Seine, where now stands the palace of the Institute. It came into the hands of the crown, was the scene of events recorded by Brantôme, and was bought by Cardinal Mazarin as the site for his college.

Ness, LOCH, a long, narrow lake of Invernessshire, the second largest in Scotland, 6 miles SW. of Inverness. Lying some 50 feet above sea-level, it extends 241 miles north-north-eastward, and has an average breadth of 1 mile, with an area of 21 sq. m. It receives the Morriston, Oich, Foyers (q.v.), and other streams, and sends off the river Ness to the Moray Firth. It lies in the valley of Glenmore, on the line of the Caledonian Canal (q.v.), and is enclosed by steep mountains-the highest, Mealfourvonie (2284 feet). Owing to its great depth (maximum 754 feet) it never freezes to any considerable extent. See FORT Augustus. Nesselrode, KARL ROBERT, COUNT, Russian diplomatist, was born on the 14th December 1780, at Lisbon, where his father, a descendant of an ancient noble family on the lower Rhine, was then Russian ambassador. He gained in a high degree the esteem and confidence of the Emperor Alexander, and in 1814 he accompanied the Russian emperor to France, where he took a principal part in all the negotiations which ended in the peace of Paris; and he was one of the most prominent of the plenipotentiaries in the Congress of Vienna, and one of the most active diplomatists of the Holy Alliance. The Emperor Nicholas reposed in him the same confidence, and amidst the European convulsions of 1848 and 1849 Russia, under his guidance, refrained from interference, till an opportunity occurred of dealing a deadly blow to the revolutionary cause in Hungary. Being one of the chiefs of the moderate party in Russia, Nesselrode exerted himself to preserve peace with the Western Powers; and after the war had broken out in 1854 he undoubtedly strove for the re-establishment of peace. After the accession of Alexander II. he retired from the direction of foreign affairs, and was succeeded by Prince Alexander Gortschakoff, but retained the dignity of chancellor of the empire. He died 23d March 1862, and his autobiography appeared at Berlin in 1866, his Lettres et Papiers in 1904-11. Nessus. See HERCULES.

Nestor, according to ancient Greek legend, the son of Neleus and Chloris, born in the Messenian Pylos, escaped destruction when Hercules slew all his brothers. He married Eurydice, by whom he became the father of a numerous family. In his youth he was distinguished for valour in wars with

the Arcadians, Eleians, and the Centaurs, and in his advanced age for wisdom. Although he was an old man when the expedition against Troy was undertaken, he joined it with his Pylians in sixty ships. Homer makes him the great counsellor of the Greek chiefs, and extols his eloquence as superior even to that of Ulysses. Nestor returned in safety to his own dominions after the fall of Troy, and continued for long to rule over the people of Pylos.-For the birds called Nestor, see KEA.

Nestorius, a native of Germanicia, a city of northern Syria, in the patriarchate of Antioch, was probably a disciple of the celebrated Theodore of Mopsuestia. Having received priest's orders at Antioch, he became so eminent for his zeal, ascetic life, and eloquence in preaching that he was selected by the emperor as patriarch of Constantinople (April 428). Soon after his consecration a controversy arose as to the divine and human natures of our Lord, in which Nestorius took a leading part. The presbyter Anastasius, having in a sermon denied that the Virgin Mary could be truly called the Mother of God (EOTÓKOS), it being not God the Logos but only the human nature which had a mother and suffered pain and death, Nestorius warmly defended Anastasius, and elaborated his view into the theory which has since been known by his name. He held that Mary was the Mother of Christ (XpOTOTÓKOS), or the Receiver or Conceiver of God (@codoxos), and that, while the divinity of the Logos is to be distinguished from the temple of his flesh, yet there remained but one person in the God-man. By his antagonists he was accused of exaggerating the distinction of two natures into a co-existence of two persons (πроow voois)-the human person of Christ and the Divine Person of the Word. A vigorous controversy ensued, which extended from Constantinople to the other patriarchates, and drew from Cyril of Alexandria a formal condemnation of the doctrine of Nestorius in twelve anathemas, and a similar condemnation, accompanied by a threat of deposition and excommunication, from Celestine, Bishop of Rome, unless he would withdraw the obnoxious doctrine. Nestorius remaining firm in his opinions, a general council was convened at Ephesus in 431, at which Cyril took the most active and prominent part, and in which, notwithstanding the absence of John the Patriarch of Antioch and his bishops, Nestorius was condemned and deposed. Considerable opposition was offered to this judgment for a time, but ultimately the emperor was led to side with Cyril. Nestorius was confined in a monastery, aud, after four years, banished to Petra in Arabia. He next found shelter in the Greater Oasis in Upper Egypt, and, after several changes of his place of confinement, died in exile, time and place alike unknown. His Bazaar of Heracleides of Damascus shows that he must have (451), and that he was himself opposed to the been alive just before the Council of Chalcedon condemned. so-called Nestorianism that the Council of Ephesus

See Bethune-Baker, Nestorius and his Teaching (1908); F. Loofs, Nestoriana (1905), and Nestorius and his Position in the History of Christian Doctrine (1914); and his own Bazaar of Heracleides (ed. Bedjan, 1910; trans. Driver and Hodgson, 1925).

The sect of the NESTORIANS, formed in the 5th century, was, after its exclusion from the Roman empire, extended into Persia, India, and even China. The teachers who were driven out of Edessa (489) settled at Nisibis, which soon became an active centre of learning and missionary enterprise throughout Persia. Babæus, Bishop of Seleucia (498-503), assumed the title of patriarch, and under his successors the sect grew rapidly and produced many learned theologians and philoso

The

phers, and not a few very eminent physicians. Under the rule of the khalifs the Nestorians enjoyed toleration, and spread in Arabia, Syria, and Palestine, and even to Samarkand, Herat, and China. The Prester John (q.v.) of romance was a Christian of this colour, and there is a tradition that Mohammed learned what he knew of Christianity from Sergius, a Nestorian monk. In the middle of the 13th century as many as twentyfive metropolitans owned the jurisdiction of the Nestorian patriarch, but after the persecutions of Tamerlane they dwindled away. Meantime the Roman Catholic Church had been active in missionary labours amongst them. In the 16th century a great schism took place, a portion renouncing their distinctive doctrine, and placing themselves under the jurisdiction of the Roman pontiff, to whom, under the title of Chaldean Christians, they have since remained faithful. Their patriarchs still bear the traditional name of Joseph. others to the present day maintain their old creed and their ancient organisation. Their chief seat is Kotchanes, near Djulamerk, in the mountainranges of Kurdistan. They are at present a poor and illiterate race. Their patriarch since the close of the 17th century has borne the name of Simeon. The bishops are bound to observe celibacy, but marriage is permitted to the priests and inferior clergy. Their liturgical books recognise seven sacraments, but confession is infrequent, if not altogether disused. Marriage is dissoluble by the sentence of the patriarch; communion is administered in both kinds; and although the language of the liturgy plainly implies the belief in transubstantiation, yet that doctrine is not popularly held among them. The fasts are strict, and of very long duration, amounting to very nearly onehalf of the entire year. They pray for the dead, but are said to reject the notion of purgatory, and the only sacred symbol which they use or reverence is the cross. The Nestorians of Kurdistan, like the Christians of the Lebanon, have suffered much from time to time through the fanaticism of the wild tribes among whom they reside. There has been among them since 1834 an active American mission, which has translated the Bible into their speech-a dialect of the old Aramaic.

There is another body of Nestorians who have existed in south India from the period of the early migrations of the sect, known as Syrian Christians or Christians of St Thomas (see THOMAS, CHRISTIANS OF ST), and works there noted.

See GREEK CHURCH; Maclean, The Catholicos of the East and his People (1892); Parry, Six Months in a Syrian Monastery (1895); Hefele's Councils; Perkins's Residence of Eight Years in Persia among the Nestorian Christians (Andover, 1843); Badger's Nestorians and their Rituals (1852); Anderson's Oriental Churches (1872); Dean Stanley's History of the Eastern Church; Wigram, The Assyrian Church (1910); Heazell and Margoliouth, Kurds and Christians (1913); and books on the Nestorian monument at Si-ngan-fu in China by Legge (1888), Havret (Variétés Sinologiques, 1898), Carus (1909), and Saeki (1916).

Nests, structures prepared for egg-laying, brooding, and nursing. The word is also applied to a shelter for the adult animals, apart from eggs or young, Nest-making reaches its finest expression in birds, but many other kinds of animals make nests-e.g. squirrels and harvest-mice, sticklebacks in the shore-pool and Antennarius among the Sargasso Weed, some spiders, and many insects like bees and wasps. See ANT, BEE, BIRD, &c. ; Alfred Russel Wallace in Contributions to the Theory of Natural Selection; C. Lloyd Morgan's Habit and Instinct (1897); W. P. Pycraft's History of Birds (1910); J. Arthur Thomson's Biology of the Seasons (1911).

NETHERSOLE

EDIBLE BIRDS' NEST, a nest chiefly composed by the consolidated whitish isinglass-like mucous secretion formed by the salivary glands of diminutive swifts belonging to the genus Collocalia. About a dozen species are known in the Indian and Australian regions; they nest in caves which are also tenanted by bats, and they fasten their saucer-shaped nests to the walls. In some species there may be an admixture of seaweed, lichen, moss, feathers, &c., along with the salivary secretion; or this may be the case when the bird makes a second nest after the first has been removed. The nests of the Esculent Swiftlet (C. fuciphaga) are particularly pure, and over 3 millions have been known to be exported from Borneo alone

The Edible Nest of the Swiftlet of South Java.

in one year. They are used in various Chinese their weight in silver. The import to Canton has 'birds' nest soups,' and are often said to be worth sometimes amounted to 25 million nests in a year. The birds are occasionally called Salangane, from one of the islands which they frequent. The nests that the chief constituent was allied to mucin. A have been analysed by Dr J. R. Green, who found similar material is secreted by many animals, and many swifts use it in glueing the materials of their nests. What is peculiar in Collocalia is that the The persistent belief that the mucilage of the nest secretion of the salivary glands is very copious. is partly extrinsic, and derived from seaweed, fishspawn, and the like, seems unwarranted. See articles by Green, Layard, and Pryer in Nature, vols. xxx.-xxxiv.; Green in Journal of Physi ology, vi. pp. 40-45; Pryer in Proc. Zoological Soc., 1885, pp. 532-58; Annandale in Chambers's Journal (1901); McGregor, Philippine Birds (1909); and Newton's Dictionary of Birds (1896),

p. 936.

Netherlands, the north-west corner of the great north European plain, a triangular region between France, Germany, and the sea, lying mainly in the basins of the Scheldt, the Meuse, and the lower Rhine, is now divided into nearly equal parts between the kingdoms of Holland and Belgium. The official designation of Netherlands is retained by what we commonly call Holland (q.v.), and under that head the early history common to the two is discussed; while the history of the 'Spanish Netherlands' falls mainly under the head of Flanders (q.v.) and Belgium (q.v.). The history of the Dutch and Flemish language and literature will be found under HOLLAND.

Netherlands Company. See JAVA.

Nethersole, OLGA, an actress born in London in 1870, who made her début at Brighton in 1887, and from 1889 played at the Garrick under John Hare. She became lessee and manager of the Court Theatre in 1894, subsequently managed the