summit and sides of an irregular ridge, and command magnifi- | a mythical seer and priest, the pupil or son of Orpheus, who was cent views over forest-clad hills and deep valleys, studded with said to have been the founder of priestly poetry in Attica. villages and cultivated fields, with the snow-covered peaks of According to Pausanias (i. 25) he was buried on the Museum hill, Kashmir in the background. The population in 1901 was 1844; south-west of the Acropolis. He composed dedicatory and but these figures omit the summer visitors, who probably number purificatory hymns and prose treatises, and oracular responses. 10,000. The garrison generally consists of three mountain These were collected and arranged in the time of Peisistratus batteries. Since 1877 the summer offices of the provincial by Onomacritus, who added interpolations. The mystic and The Murree oracular verses and customs of Attica, especially of Eleusis, are connected with his name (Herod. vii. 6; viii. 96; ix. 43). government have been transferred to Simla. (2) The brewery, one of the largest in India, is the chief industrial (G. Kinkel, Epicorum graecorum fragmenta, 1878). establishment. The Lawrence Military Asylum for the children A Titanomachia and Theogonia are also attributed to him of European soldiers is situated here. second was an Ephesian attached to the court of the kings of Pergamum, who wrote a Perseis, and poems on Eumenes and Attalus (Suīdas, s.v.). (3) The third (called Grammaticus in all the MSS.) is of uncertain date, but probably belongs to the beginning of the 6th century A.D., as his style and metre are Agathias (530-582) and is possibly to be identified with the evidently modelled after Nonnus. He must have lived before friend of Procopius whose poem (340 hexameter lines) on the story of Hero and Leander is by far the most beautiful of the age (editions by F. Passow, 1810; G. H. Schäfer, 1825; C. Dilthey, 1874). The little love-poem Alpheus and Arethusa (Anthol. pal. ix. 362) is also ascribed to Musaeus. MURSHIDABAD, or MOORSHEEDABAD, a town and district of British India, in the Presidency division of Bengal. The administrative headquarters of the district are at Berhampur. The town of Murshidabad is on the left bank of the Bhagirathi or old sacred channel of the Ganges. Pop. (1901), 15,168. The city of Murshidabad was the latest Mahommedan capital of Bengal. In 1704 the nawab Murshid Kulia Khan changed the seat of government from Dacca to Maksudabad, which he The great family of Jagat Seth called after his own name. maintained their position as state bankers at Murshidabad from generation to generation. Even after the conquest of Bengal by the British, Murshidabad remained for some time the seat of administration. Warren Hastings removed the supreme civil and criminal courts to Calcutta in 1772, but in 1775 the latter court was brought back to Murshidabad again. In 1790, under Lord Cornwallis, the entire revenue and judicial staffs were fixed at Calcutta. The town is still the residence of the nawab, who ranks as the first nobleman of the province with the style of nawab bahadur of Murshidabad, instead of His palace, dating from 1837, is a nawab nazim of Bengal. magnificent building in Italian style. The city is crowded with other palaces, mosques, tombs, and gardens, and retains such industries as carving in ivory, gold and silver embroidery, and silk-weaving. A college is maintained for the education of the nawab's family. gens. | MUSA KHEL, a Pathan tribe on the Dera Ghazi Khan border of the Punjab province of India. They are of Kakar origin, numbering 4670 fighting men. They enter British territory by the Vihowa Pass, and carry on an extensive trade, but are not dependent on India for the necessaries of life. They are a peaceful and united race, and have been friendly to the British, but at enmity with the Khetrans and the Baluch tribes to the south of their country. In 1879 the Musa Khels and other Pathan tribes to the number of 5000 made a demonstration against Vihowa, but the town was reinforced and they dispersed. In 1884 they were punished, together with the Kakars, by the Zhob Valley Expedition. MUSÄUS, JOHANN KARL AUGUST (1735-1787), German author, was born on the 29th of March 1735 at Jena, studied of a parish but for the resistance of some peasants, who objected theology at the university, and would have become the pastor that he had been known to dance. In 1760 to 1762 he published in three volumes his first work, Grandison der Zweite, afterwards Grandison. The object of this book was to satirize Samuel (in 1781-1782) rewritten and issued with a new title, Der deutsche Germany. In 1763 Musäus was made master of the court pages Richardson's hero, who had many sentimental admirers in at Weimar, and in 1769 he became professor at the Weimar appear until 1778-1779. It was directed against Lavater, and gymnasium. His second book-Physiognomische Reisen-did not attracted much favourable attention. In 1782 to 1786 he published his best work Volksmärchen der Deutschen. Even among the people, he could not refrain from satire. The stories, in this series of tales, the substance of which Musäus collected was issued Freund Heins Erscheinungen in Holbeins Manier by therefore, lack the simplicity of genuine folk-lore. In 1785 J. R. Schellenberg, with explanations in prose and verse by a volume appeared in 1787, Musäus was prevented from comMusäus. A collection of stories entitled Straussfedern, of which pleting by his death on the 28th of October 1787. The DISTRICT OF MURSHIDABAD has an area of 2143 sq. m. It is divided into two nearly equal portions by the Bhagirathi, the ancient channel of the Ganges. The tract to the west, known as the Rarh, consists of hard clay and nodular limestone. The general level is high, but interspersed with marshes and seamed by hill torrents. The Bagri or eastern half belongs to alluvial plains of eastern Bengal. There are few permanent swamps; but the whole country is low-lying, and liable to annual inundation. In the north-west are a few small detached hillocks, said to be of basaltic formation. Pop. (1901), 1,333,184, showing an increase of 6·6% in the decade. The principal industry is that of silk, formerly of much importance, and now revived with government assistance. A narrow-gauge railway crosses the district, from the East Indian line at Nalhati to Azimganj on the Bhagirathi, the home of many rich Jain merchants; and a branch of the Eastern Bengal railway has been opened. MUS, the name of a Roman family of the plebeian Decian (1) PUBLIUS DECIUS Mus won his first laurels in the Samnite War, when in 343 B.C., while serving as tribune of the soldiers, he rescued the Roman main army from an apparently hopeless position (Livy vii. 34). In 340, as consul with T. Manlius Torquatus as colleague, he commanded in the Latin War. The decisive battle was fought near Mt Vesuvius. The consuls, in consequence of a dream, had agreed that the general whose troops first gave way should devote himself to destruction, and so ensure victory. The left wing under Decius became disordered, whereupon, repeating after the chief pontiff MUSCAT, MUSKAT or MASKAT, a town on the south-east the solemn formula of self-devotion he dashed into the ranks coast of Arabia, capital of the province of Oman. Its value of the Latins, and met his death (Livy viii. 9). (2) His son, as a naval base is derived from its position, which commands also called PUBLIUS, consul for the fourth time in 295, followed the example of his father at the battle of Sentinum, when the left wing which he commanded was shaken by the Gauls (Livy the entrance to the Persian Gulf. The town of Gwadar, the L 28). The story of the elder Decius is regarded by Mommsen chief port of Makran, belongs to Muscat, and by arrangement "doublette" of what is related on better with the sultan the British occupy that port with a telegraph station of the Indo-Persian telegraph service. An Indian an unhistorical hority of the son. MUSAEUS, the name of three Greek poets. (1) The first was political residency is established at Muscat. In geographical The Volksmärchen have been frequently reprinted (Düsseldorf, 1903, &c.). They were translated into French in 1844, and three of the stories are included in Carlyle's German Romance (1827); Musaus's Nachgelassene Scriften were edited by his relative, A. von Kotzebue (1791). See M. Müller, J. K. A. Musäus (1867), and an essay by A. Stern in Beiträge zur Literaturgeschichte des 18. Jahrhunderts (1893). position it is isolated from the interior of the continent. The mountains rise behind it in a rugged wall, across which no road exists. It is only from Matrah, a northern suburb shut off by an intervening spur which reaches to the sea, that land communication with the rest of Arabia can be maintained. Both Muscat and Matrah are defended from incursions on the landward side by a wall with towers at intervals. Muscat rose to importance with the Portuguese occupation of the Persian Gulf, and is noted for the extent of Portuguese ruins about it. Two lofty forts, of which the most easterly is called Jalāli and the western Merani, occupy the summits of hills on either side the cove overlooking the town; and beyond them on the seaward side are two smaller defensive works called Sirat. All these are ruinous. A low sandy isthmus connects the rock and fortress of Jalali with the mainland, and upon this isthmus stands the British residency. The sultan's palace is a three-storeyed building near the centre of the town, a relic of Portuguese occupation, called by the Arabs El Jereza, a corruption of Igrezia (church). This term is probably derived from the chapel once attached to the buildings which formed the Portuguese governor's residence and factory. The bazaar is insignificant, and its most considerable trade appears to be in a sweetmeat prepared from the gluten of maize. Large quantities of dates are also exported. History. The early history of Muscat is the history of Portuguese ascendancy in the Persian Gulf. When Albuquerque first burnt the place after destroying Karyāt in 1508, Kalhat was the chief port of the coast and Muscat was comparatively unimportant. Kalhat vas subsequently sacked and burnt, the great Arab mosque being destroyed, before Albuquerque returned to his ships, "giving many thanks to our Lord." From that date, through 114 years of Portuguese ascendancy, Muscat was held as a naval station and factory during a period of local revolts, Arab incursions, and Turkish invasion by sea; but it was not till 1622, when the Portuguese lost Hormuz, that Muscat became the headquarters of their fleet and the most important place held by them on the Arabian coast. In 1650 the Portuguese were finally expelled from Oman. Muscat had been reduced previously by the humiliating terms imposed upon the garrison by the imam of Oman after a siege in 1648. For five years the Persians occupied Oman, but they disappeared in Under the great ruler of Oman, Said ibn Sultan (18041856), the fortunes of Muscat attained their zenith; but on his death, when his kingdom was divided and the African possessions were parted from western Arabia, Muscat declined. In 18831884, when Turki was sultan, the town was unsuccessfully besieged by the Indabayin and Rehbayin tribes, led by Abdul Aziz, the brother of Turki. In 1885 Colonel Miles, resident at Muscat, made a tour through Oman, following the footsteps of Wellsted in 1835, and confirmed that traveller's report of the fertility and wealth of the province. In 1898 the French acquired the right to use Muscat as a coaling station. 1741. - See Stiffe," Trading Ports of Persian Gulf," vol. ix. Geog. Journal, and the political reports of the Indian government from the Persian Gulf. Colonel Miles's explorations in Oman will be found in vol. vii. Geog. Journal (1896).– (T. H. H.*) MUSCATINE, a city and the county-seat of Muscatine county, Iowa, U.S.A., on the Mississippi river (here crossed by a wagon bridge), at the apex of the " great bend," in the south-east part of the state. Pop. (1890), 11,454; (1900), 14,073, of whom 2352 were foreign-born; (1910 census) 16,178. It is served by the Chicago Milwaukee & Saint Paul, the Chicago Rock Island & Pacific, and the Muscatine North & South railways. It is built on high rocky bluffs, and is the centre of a pearlbutton industry introduced in 1891 by J. F. Boepple, a German, the buttons being made from the shells of the fresh-water mussel found in the neighbourhood; and there are other manufactures. Coal is mined in the vicinity, and near the city are large market-gardens, the water-melons growing on Muscatine Island (below the city) and sweet potatoes being their most important products. The municipality owns and operates the waterworks. Muscatine began as a trading-post in 1833. It was laid out in 1836, incorporated as a town under the name of Bloomington in 1839, and first chartered as a city, under its present name, in 1851. MUSCHELKALK, in geology, the middle member of the German Trias. It consists of a series of calcareous, marly and dolomitic beds which lie conformably between the Bunter and Keuper formations. The name Muschelkalk (Fr., calcaire coquillier; conchylien, formation of D'Orbigny) indicates a characteristic feature in this series, viz. the frequent occurrence of lenticular banks composed of fossil shells, remarkable in the midst of a singularly barren group. In its typical form the Muschelkalk is practically restricted to the German region and its immediate neighbourhood; it is found in Thuringia, Harz, Franconia, Hesse, Swabia, and the Saar and Alsace districts. Northward it extends into Silesia, Poland and Heligoland. Representatives are found in the Alps, west and south of the Vosges, in Moravia, near Toulon and Montpellier, in Spain and Sardinia; in Rumania, Bosnia, Dalmatia, and beyond this into Asia in the Himalayas, China, Australia, California, and in North Africa (Constantine). From the nature of the deposits, as well as from the impoverished fauna, the Muschelkalk of the type area was probably laid down within a land-locked sea which, in the earlier portion of its existence, had only imperfect communications with the more open waters of the period. The more remote representatives of the formation were of course deposited in diverse conditions, and are only to be correlated through the presence of some of the Muschelkalk fossils. In the "German area the Muschelkalk is from 250-350 ft. thick; it is readily divisible into three groups, of which the upper and lower are pale thin-bedded limestones with greenishgrey marls, the middle group being mainly composed of gypsiferous and saliniferous marls with dolomite. The Lower Muschelkalk consists, from below upwards, of the following rocks, the ochreous Wellen Dolomit, lower Wellen Kalk, upper Wellen Kalk (so called on account of the wavy character of the bedding) with beds of "Schaumkalk" (a porous cellular limestone), and Oolite and the Orbicularis beds (with Myophoria orbicularis). In the Saar and Alsace districts and north Eifel, these beds take on a sandy aspect, the "Muschelsandstein." The Middle Muschelkalk or Anhydrite group, as already indicated, consists mainly of marls and dolomites with beds of anhydrite, gypsum and salt. The salt beds are worked at Hall, Friedrichshall, Heilbronn, Stettin and Erfurt. It is from this division that many of the mineral springs of Thuringia and south Germany obtain their saline contents. The cellular nature of much of the dolomite has given rise to the term "Zellendolomit." The Upper Muschelkalk (Hauptmuschelkalk, Friedrichshallkalk of von Alberti) consists of regular beds of shelly limestone alternating with beds of marl. The lower portion or "Trochitenkalk " is often composed entirely of the fragmentary stems of Encrinus liliiformis; higher up come the "Nodosus beds with Ceratites compressus, C. nodosus, and C. semipartitus in ascending order. In Swabia and Franconia the highest beds are platy dolomites with Tringonodus Sandergensis and the crustacean Bairdia. Stylolites are common in all the Muschelkalk limestones. The Alpine Muschelkalk differs in many respects from that of the type area, and shows a closer relationship with the Triassic Mediterranean sea; the more important local phases will be found tabulated in the article TRIAS. In addition to the fossils mentioned above, the following are Muschelkalk forms: Terebratulina vulgaris, Spiriferina Mantzeli Münsteri, Plychites studeri, Balatonites balatonicus, Aspidura scuteland S. hirsuta, Myophoria vulgaris, Rhynchotites hirundo, Ceratites lata, Daonella Lommeli, and in the Alpine region several rockforming Algae, Bactryllium, Gyroporella, Diplopora, &c. (J. A. H.) MUSCLE AND NERVE (Physiology). Among the properties of living material there is one, widely though not universally present in it, which forms the pre-eminent characteristic of 1 The anatomy of the muscles is dealt with under MUSCULAR SYSTEM, and of the nerves under NERVE and NERVOUS SYSTEM Muscle. Contractlbility. 45 muscular cells. This property is the liberation of some of | quickly as to fall even during the continuance of the contraction the energy contained in the chemical compounds of the cells excited by a first, elicits a second contraction. This second in such a way as to give mechanical work. The contraction starts from whatever phase of previous contraction mechanical work is obtained by movement resulting the muscle may have reached at the time. A third stimulus from a change, it is supposed, in the elastic tension of the excites a third additional contraction, a fourth a fourth, and so framework of the living cell. In the fibrils existing in the on. cell a sudden alteration of elasticity occurs, resulting in an less, until the succeeding stimuli serve merely to maintain, not increased tension on the points of attachment of the cell to the to augment, the existing degree of contraction. We arrive thus The increments of contraction become, however, less and neighbouring elements of the tissue in which the cell is placed. by synthesis at a summation of "beats" or of simple contracThese yield under the strain, and the cell shortens between tions in the compound, or " tetanic," or summed contraction of those points of its attachment. This shortening is called the skeletal muscles. The tetanic or summed contractions are contraction. But the volume of the cell is not appreciably altered, despite the change of its shape,liberate more energy, both as mechanical work and heat. The more extensive than the simple, both in space and time, and for its one diameter increases in proportion as its tension developed by their means in the muscle is many times other is diminished. The manifestations of contractility by greater than that developed by a simple twitch. muscle are various in mode. By tonic contraction is meant a prolonged and equable state of tension which yields under in their environment, and thus are said to be analysis no element of intermittent character. This is mani- They are, however, less excitable than are the nerve Muscle cells respond by changes in their activity to changes fested by the muscular walls of the hollow viscera and of the cells which innervate them. The change which heart, where it is the expression of a continuous liberation of excites them is termed a stimulus. excitable.' energy in process in the muscular tissue, the outcome of the stimulus which suffices to excite is known as the stimulus of latter's own intrinsic life, and largely independent of any con- threshold value. In the case of the heart muscle this threshold The least nexion with the nervous system. The muscular wall of the stimulus evokes a beat as extensive as does the strongest blood-vessels also exhibits tonic contraction, which, however, stimulus; that is, the intensity of the stimulus, so long as it scems to be mainly traceable to a continual excitation of the is above threshold value, is not a function of the amount of the muscle cells by nervous influence conveyed to them along their muscular response. nerves, and originating in the great vaso motor centre in the bulb. amount of the muscular contraction is for a short range of In the ordinary striped muscles of the skeletal musculature, e.g. But in the ordinary skeletal muscles the gastrocnemius, tonic contraction obtains; but this, like the last mentioned, is not autochthonous in the muscles themselves; it❘ of stimulus, however, is soon reached which evokes a maximal quantities of stimulus (of above threshold value) proportioned to the intensity of the stimulus and increases with it. A value is indirect and neural, and appears to be maintained reflexly. contraction. Further increase of contraction does not follow The receptive organs of the muscular sense and of the semi- further increase of the intensity of the stimulus above that circular canals are to be regarded as the sites of origin of this point reflex tonus of the skeletal muscles. Striped muscles possessing an autochthonous tonus appear to be the various sphincter muscles. Another mode of manifestation of contractility by muscies is the rhythmic. A tendency to rhythmic contraction seems discoverable in almost all muscles. In some it is very marked, for example in some viscera, the spleen, the bladder, the ureter, the uterus, the intestine, and especially in the heart. In several of these it appears not unlikely that the recurrent explosive liberations of energy in the muscle tissue are not secondary to recurrent explosions in nerve cells, but are attributable to decompositions arising sua sponte in the chemical substances of the muscle cells themselves in the course of their living. Even small strips of the muscle of the heart, if taken immediately after the death of the animal, continue, when kept moist and warm and supplied with oxygen, to "beat" rhythmically for hours. Rhythmic contraction is also characteristic of certain groups of skeletal muscles, e.g. the respiratory. In these the rhythmic activity is, however, clearly secondary to rhythmic discharges of the nerve cells constituting the respiratory centre in the bulb. Such discharges descend the nerve fibres of the spinal cord, and through the intermediation of various spinal nerve cells excite the respiratory muscles through their motor nerves. contraction intermediate in character between the tonic and A form of the rhythmic is met in the auricle of the heart of the toad. There slowly successive phases of increased and of diminished tonus regularly alternate, and upon them are superposed the rhythmic "beats" of the pulsating heart. "The beat," i.e. the short-lasting explosive contraction of the heart muscle, can be elicited by a single, even momentary, application of a stimulus, e.g. by an induction shock. Similarly, such a single stimulus elicits from a skeletal muscle a single "beat," or, as it is termed, a during a brief period after each beat, that is, after each "twitch." In the heart muscle single contraction of the rhythmic series, the muscle becomes inexcitable. It cannot then he excited to contract by any agent, though the inexcitable period is more brief for strong than for weak stimuli. But in the skeletal, voluntary or striped muscles a second stimulus succeeding a previous so Excitability. the excited state spreads from the excited point to the adjacent Just as in a nerve fibre, when excited by a localized stimulus, in muscle and in nerve this spread is termed conduction. unexcited ones, so in muscle the "contraction," when excited at a point, spreads to the adjacent uncontracted parts. Both It is propagated along the muscle fibres of the skeletal muscles at a rate of about 3 metres per second. In the heart muscle it travels much more slowly. The disturbance travels as a disturbance measures in ordinary muscles much more than the wave of contraction, and the whole extent of the wave-like whole length of any single muscle fibre. That the excited state spreads only to previously unexcited portions of the muscle fibre shows that even in the skeletal variety of muscle there exists, though only for a very brief time, a period of inexcitability. The duration of this period is about of a second in skeletal muscle. excited by a series of single and equal stimuli succeeding at When muscle that has remained inactive for some time is intervals too prolonged to cause summation the succeeding contractions exhibit progressive increase up to a certain degree. The tenth contraction usually exhibits the culmination of this so-called doses, favours the contractile power of muscle. The muscle staircase effect." The explanation may lie in the production of CO2 in the muscle. That substance, in small is a machine for utilizing the energy contained in its own chemical compounds. It is not surprising that the chemical substances produced in it by the decomposition of its living material should if the series of excitations of the muscle be prolonged beyond not be of a nature indifferent for muscular life. We find that the short stage of initial improvement, the contractions, after being well maintained for a time, later decline in force and speed, and ultimately dwindle even to vanishing point. This decline is said to be due to muscular fatigue. The muscle and more quickly on being washed with an innocuous but nonnutritious solution, such as 6%, NaCl in water. The washing recovers on being allowed to rest unstimulated for a while, by breaking them down into innocuous material. Since the seems to remove excreta of the muscle's own production, and the period of repose removes them perhaps by diffusion, perhaps of Neuron. muscle produces lactic acids during activity, it has been sug-| Non-myelinate nerve fibres are as resistant to fatigue as are gested that acids are among the "fatigue substances" with the myelinate. which muscle poisons itself when deprived of circulating blood. Muscles when active seem to pour into the circulation substances which, of unknown chemical composition, are physiologically recognizable by their stimulant action on the respiratory nervous centre. The effect of the fatigue substances upon the contraction of the tissue is manifest especially in the relaxation process. The contracted state, instead of rapidly subsiding after discontinuance of the stimulus, slowly and only partially wears off, the muscle remaining in a condition of physiological "contracture." The alkaloid veratrin has a similar effect upon the contraction of muscle; it enormously delays the return from the contracted state, as also does epinephrin, an alkaloid extracted from the suprarenal gland. Neuron Theory. Nervous System.-The work of Camillo Golgi (Pavia, 1885 and onwards) on the minute structure of the nervous system has led to great alteration of doctrine in neural physiology. It had been held that the branches of the nerve cells, that is to say, the fine nerve fibressince all nerve fibres are nerve cell branches, and all nerve cell branches are nerve fibres-which form a close felt-work in the nervous centres, there combined into a network actually continuous throughout. This continuum was held to render possible conduction in all directions throughout the grey matter of the whole nervous system. The fact that conduction occurred preponderantly in certain directions was explained by appeal to a hypothetical resistance to conduction which, for reasons unascertained, lay less in some directions than in others. The intricate felt-work has by Golgi been ascertained to be a mere interlacement, not an actual anastomosis network; the branches springing from the various cells remain lifelong unattached and unjoined to any other than their own individual cell. Each neuron or nerve cell is a morphologically distinct and discrete unit connected functionally but not structurally with its neighbours, and leading its own life independently of the destiny of its neighbours. Among the properties of the neuron is conductivity in all directions. But when neurons are linked together it is found that nerve impulses will only pass from neuron A to neuron B, and not from neuron B to neuron A; that is, the transmission of the excited state or nervous impulse, although possible in each neuron both up and down its own cell branches, is possible from one nerve cell to another in one direction only. That direction is the direction in which the nerve impulses flow under the conditions of natural life. The synapse, therefore, as the place of meeting of one neuron with the next is called, is said to valve the nerve circuits. This determinate sense of the spread is called the law of forward direction. The synapse appears to be a weak spot in the chain of conduction, or rather to be a place which breaks down with comparative ease under stress, c.g. under effect of poisons. The axons of the motor neurons are, inasmuch as they are nerve fibres in nerve trunks, easily accessible to artificial stimuli. It can be demonstrated that they are practically indefatigable-repeatedly stimulated by electrical currents, even through many hours, they, unlike muscle, continue to respond with unimpaired reaction. Peripheral Yet when the muscular contraction is taken as index Fatigue. of the response of the nerve, it is found that unmistakable signs of fatigue appear.even very soon after commencement of the excitation of the nerve, and the muscle ceases to give any contraction in response to stimuli applied indirectly to it through its nerve. But the muscle will, when excited directly, e.g. by direct application of electric currents, contract vigorously after all response on its part to the stimuli (nerve impulses) applied to it indirectly through its nerve has failed. The inference is that the "fatigue substances generated in the muscle fibres in the course of their prolonged contraction injure and paralyse the motor end plates, which are places of synapsis between nerve cell and muscle cell, even earlier than they harm the contractility of the muscle fibres themselves. The alkaloid curarin causes motor paralysis by attacking in a selective way this junction of motor nerve cell and striped muscular fibre. I The neuron is described as having a cell body or perikaryon from which the cell branches-dendrites and axon-extend, and it is this perikaryon which, as its name implies, contains the nucleus. It forms the trophic centre of Solidarity the cell, just as the nucleus-containing part of every cell is the trophic centre of the whole cell. Any part of the cell cut off from the nucleus-containing part dies down: this is as true of nerve cells as of amoeba, and in regard to the neuron it constitutes what is known as the Wallerian degeneration. On the other hand, in some neurons, after severance of the axon from the rest of the cell (spinal motor cell), the whole nerve cell as well as the severed axon degenerates, and may eventually die and be removed. In the severed axon the degeneration is first evident in a breaking down of the naked nerve filaments of the motor end plate. A little later the breaking down of the whole axon, both axis cylinder and myelin sheath alike, seems to occur simultaneously throughout its entire length distal to the place of severance. The complex fat of the myelin becomes altered chemically, while the other components of the sheath break down. This death of the sheath as well as of the axis cylinder shows that it, like the axis cylinder, is a part of the nerve cell itself. ·Tonic Activity of In addition to the trophic influence exerted by each part of the neuron on its other parts, notably by the perikaryon on the cell branches, one neuron also in many instances influences the nutrition of other neurons. When, for instance, the axons of the ganglion cells of the retina are severed by section of the optic nerve, and thus their influence upon the nerve cells of the visual cerebral centres is set aside, the nerve cells of those centres undergo secondary atrophy (Gadden's atrophy). They dwindle in size; they do not, however, die. Similarly, when the axons of the motor spinal cells are by severance of the nerve trunk of a muscle broken through, the muscle cells undergo "degeneration "-dwindle, become fatty, and alter almost beyond recognition. This trophic influence which one neuron exerts upon others, or upon the cells of an extrinsic tissue, such as muscle, is exerted in that direction which is the one normally taken by the natural nerve impulses. It seems, especially in Neurons. the case of the nexus between certain neurons, that the influence, loss of which endangers nutrition, is associated with the occurrence of something more than merely the nervous impulses awakened from time to time in the leading nerve cell. The wave of change (nervous impulse) induced in a neuron by advent of a stimulus is after all only a sudden augmentation of an activity continuous within the neurona transient accentuation of one (the disintegrative) phase, of the metabolism inherent in and inseparable from its life. The nervous impulse is, so to say, the sudden evanescent glow of an ember continuously black-hot. A continuous lesser "change" or stream of changes sets through the neuron, and is distributed by it to other neurons in the same direction and by the same synapses as are its nerve impulses. This gentle continuous activity of the neuron is called its tonus. In tracing the tonus of neurons to a source, one is always led link by link against the current of nerve force-so to say, up stream "-to the first beginnings of the chain of neurons in the sensifacient surfaces of the body. From these, as in the eye, ear, and other sense organs, tonus is constantly, initiated. Hence, when cut off from these sources, the nutrition of the neurons of various central mechanisms suffers. Thus the tonus of the motor neurons of the spinal cord is much lessened by rupture of the great afferent root cells which normally play upon them. A prominent and practically important illustration of neural tonus is given by the skeletal muscles. These muscles exhibit a certain constant condition of slight contraction, which disappears on severance of the nerve that innervates the muscle. It is a muscular tonus of central source consequent on the continual glow of excitement in the spinal motor neuron, whose outgoing end plays upon the muscle cells, whose ingoing end is played upon by other neurons-spinal, cerebral and | to thrust out new branches and to lengthen existing branches, cerebellar. It is with the neural element of muscle tonus that lendon phenomena are intimately associated. The earliest-studied of these, the "knee-jerk," may serve as example of the class. It is a brief extension of the limb at the knee-joint, due to a simple contraction of the extensor muscle, elicited by a tap or other short mechanical stimulus applied to the muscle fibres through the tendon of the muscle. The jerk is obtainable only from muscle fibres possessed of neural tonus. If the sensory nerves of the extensor muscle be. severed, the "jerk" is lost. The brevity of the interval between the tap on the knee and the beginning of the resultant contraction of the muscle seems such as to exclude the possibility of reflex development. A little experience in observations on the knee-jerk imparts a notion of the average strength of the "jerk." Wide departures from the normal standard are met with and are symptomatic of certain nervous conditions. Stretching of the muscles antagonistic to the extensors-namely, of the flexor muscles reduces the jerk by inhibiting the extensor spinal nerve cells through the nervous impulses generated by the tense flexor muscles. Hence a favourable posture of the limb for eliciting the jerk is one ensuring relaxation of the hamstring muscles, as when the leg has been crossed upon the other. In sleep the jerk is diminished, in deep sleep quite abolished. Extreme bodily fatigue diminishes it. Conversely, a cold bath increases it. The turning of attention towards the knee interferes with the jerk; hence the device of directing the person to perform vigorously some movement, which does not involve the muscles of the lower limb, at the moment when the light blow is dealt upon the tendon. A slight degree of contraction of muscle seems the substratum of all attention. The direction of attention to the performance of some movement by the arm ensures that looseness and freedom from tension in the thigh muscles which is essential for the provocation of the jerk. The motor cells of the extensor muscles, when preoccupied by cerebral influence, appear refractory. T. Ziehen has noted exaltation of the jerk to follow extirpation of a cortical centre. Conduction Although the cell body or perikaryon of the neuron, with its contained nucleus, is essential for the maintenance of the life of the cell branches, it has become recognized la Neurons. that the actual process and function of conduction" in many neurons can, and does, go on without the cell body being directly concerned in the conduction. S. Exner first showed, many years ago, that the nerve impulse travels through the spinal ganglion at the same speed as along the other parts of the nerve trunk-that is, that it suffers no delay in transit through the perikarya of the afferent rootneurons. Bethe has succeeded in isolating their perikarya from certain of the afferent neurons of the antennule of Carcinus. The conduction through the amputated cell branches continues unimpaired for many hours. This indicates that the conjunction between the conducting substance of the dendrons and that of the axon can be effected without the intermediation of the cell body. But the proper nutrition of the conducting substance is indissolubly dependent on the cell branches being in continuity with the cell body and nucleus it contains. Evidence illustrating this nexus is found in the visible changes produced in the perikaryon by prolonged activity induced and maintained in the conducting branches of the cell. As a result the fatigued cells appear shrunken, and their reaction to staining reagents alters, thus showing chemical alteration. Most marked is the decrease in the volume of the nucleus, amounting even to 44% of the initial volume. In the myelinated cell branches of the neuron, that is, in the ordinary nerve fibres, no visible change has ever been demonstrated as the result of any normal activity, however great-a striking contrast to the observations obtained on the perikarya. The chemical changes that accompany activity in the nerve fibre must be very small, for the production of CO is barely measurable, and no production of heat is observable as the result of the most forced tetanic activity. for many years far into adult life. They similarly possess power to repair and to regenerate their cell branches where these are injured or destroyed by trauma or disease. This is the explanation of the repair of nerve trunks that have been severed, with consequent degeneration of the peripheral nerve fibres. As a rule, a longer time is required to restore the motor than the sensory functions of a nerve trunk. as emerge Cerebral Cortex. the conducting paths of the nervous system, traced from Experiment shows that in the manlike (anthropoid) apes the differentiation of the foci or "centres" of movement in the motor field of the cortex is even more minute. In them areas are found whence stimuli excite movements of this or that finger alone, of the upper lip without the lower, of the tip only of the tongue, or of one upper eyelid by itself. The movement evoked from a point of cortex is not always the same; its character is determined by movements evoked from neighbouring points of cortex immediately antecedently. Thus a point A will, when excited soon subsequent to point B, which latter yields protrusion of lips, itself yield lip-protrusion, whereas if excited after C, which yields lip-retraction, it will itself yield lip-retraction. The movements obtained by point-to-point excitation of the cortex are often evidently imperfect as compared with natural movements-that is, are only portions of complete normal movements. Thus among the tongue movements evoked by stigmatic stimulation of the cortex undeviated protrusion or retraction of the organ is not found. Again, from different points of the cortex the assumption of the requisite positions of the tongue, lips, cheeks, palate and epiglottis, as components in the act of sucking, can be provoked singly. Rarely can the whole action be provoked, and then only gradually, by prolonged and strong excitation of one of the requisite points, e.g. that for the tongue, with which the other points are functionally connected. Again, no single point in the cortex evokes the act of ocular convergence and fixation. All this means that the execution of natural movements employs simultaneous co-operative activity of a number of points in the motor fields on both sides of the brain together. The accompanying simple figure indicates better than any verbal description the topography of the main groups of foci in the motor field of a manlike ape (chimpanzee). It will be |