Muscle.

more than 300 ft. thick; and (2d) alternations of limestone, dolomite, marl, gypsum, and rock-salt, nearly 300 ft. thick. The limestone abounds in the remains of mollusca. The paleozoic goniatites are replaced by the ceratites, a remarkable link between them and the secondary ammonities. Ceratites are distinguished by the few small denticulations of the inner lobes of the suture. The heads and stems of lily encrinites (Encrinus) are also abundant in these strata, and the remains of ganoid fish have also been met with. MUSCI. See MOSSES.

MUSCICA PIDÆ, a family of birds of the order insessore and tribe dentirostres, of which the greater number receive the popular name fly-catcher (q.v.). The limits of the family are, however, very variously defined by different ornithologists. The muscicapidæ are mostly inhabitants of the warmer parts of the world, in which they are very widely diffused. The species are very numerous.

MUSCIDE, a family of dipterous insects, having a short, thick, membranous proboscis, geniculated at the base, entirely retractile so as to be concealed within the mouth, and terminated by two large lobes (see HOUSE-FLY); the antennæ three-jointed; the thorax with a transverse suture. The species are very numerous, and universally distributed. More than 800 are found in Britain, among which are the well-known housefly, blow-fly, etc. The larvæ are maggots (q.v.). Although some of the muscidæ are troublesome, none of them are so much so as species of some other allied families.

MUSCLE AND MUSCULAR TISSUE. Muscular tissue is specially distinguished by its contractile power, and is the instrument by which all the sensible movements of the animal body are performed. When examined under a high magnifying power, the fibers of which it is composed are found to exist under two forms, which can be distinguished from one another by the presence or absence of very close and minute transverse bars or stripes. The fibers of the voluntary muscles—or those whose movements can be influenced by the will-as well as the fibers of the heart, are striped; while those of the involuntary muscles-the muscular structures over which we have no control-as, for example, the muscular fibers of the intestinal canal, the uterus, and the bladder, are unstriped.

On examining an ordinary voluntary muscle with the naked eye (a muscle from one of the extremities of any animal, for example), we observe that it presents a fibrous appearance, and that the fibers are arranged with great regularity in the direction in which the muscle is to act or contract (for it is by their inherent power of contracting that muscles act). On closer examination it is found that these fibers are arranged in fasciculi, or bundles of various sizes, inclosed in sheaths of areolar tissue, by which they are at the same time connected with and isolated from those adjoining them; and when the smallest fasciculus visible to the naked eye is examined with the microscope, it is seen to consist of a number of cylindrical fibers lying in a parallel direction, and closely bound together. These primitive (or, as some writers term them, the ultimate) fibers present two sets of markings or strie-viz., a longitudinal and a transverse set. The fibers, when separated from each other, frequently split longitudinally into fibrillæ. Sometimes, however, when a fiber is extended, it separates in the direction of the transverse striæ into a series of disks. Either cleavage is equally natural, but the latter is the least common. Hence, observes Mr. Bowman, who has specially investigated the minute structure of voluntary muscle, "it is as proper to say that the fiber is a pile of disks as that it is a bundle of fibrilla; but, in fact, it is neither the one nor the other, but a mass in whose structure there is an intimation of the existence of both, and a tendency to cleave in the two directions. If there were a general disintegration along all the lines in both directions, there would result a series of particles, which may be termed primitice particles or sarcous elements, the union of which constitutes the mass of the fiber. These elementary particles are arranged and united together in the two directions, and the resulting disks, as well as fibrillæ, are equal to one another in size, and contain an equai number of particles. The same particles compose both. To detach an entire fibrilla is to extract a particle of every disk, and vice versa. The fibers are supplied with vessels and nerves, which lie in the intervals between them, and are attached by their extremities through the medium of tendon or aponeurosis to the parts which they are intended to move. Aggregated in parallel series, of greater or lesser size, and associated with nerves, vessels, tendinous structures, etc., they form the various muscles which are for the most part solid and elongated, but are sometimes expanded into a membranous shape. The length of the fibers is usually about that of the muscle in which they may occur, and may vary from two feet or more (in the sartorius muscle) to less than two lines (in the stapedius muscle in the middle ear); while their width varies from too of an inch, being largest in crustaceans, fishes, and reptiles, where their irritability, or property of contracting under the action of a stimulus, is most enduring, and smallest in birds where it is most evanescent. Their average width in man is about of an inch, being about of an inch in the male and of an inch in the female. The average distance between the striæ, or the size of the sarcous elements, in the human subject is of an inch, the extremes being and of an inch, according to the contraction or relaxation of the fiber. The form of the fibers is polygonal, their sides being flattened against those of the adjoining fibers. Each fiber is enclosed in a transparent, very delicate, but tough and elastic tubular sheath, which cannot always be readily seen, but is distinctly shown stretching between the separated fragments of a fiber

00

which has been broken within it, for its toughness will often resist a force before which its brittle contents give way. This tubular sheath is known as the sarcolemma or myolemma -the former term being derived from the Greek words sarx, flesh, and lemma, a skin or husk; and the latter from the Greek words mus, a muscle, and lemma.

It was for a long time believed that the contraction of a muscle was associated with a change in the direction of each fiber from a straight line to a sinuous or zigzag course. The investigations of Mr. Bowman, have, however, shown that this view is erroneous. He has proved that in a state of contraction there is an approximation of the transverse striæ, and a general shortening with a simultaneous thickening of the fiber, but that it is never thrown out of the straight line, except when it has ceased to contract and its extremities are acted on by the contraction of adjacent fibers.

Muscles grow by an increase, not of the number, but of the bulk of their elementary fibers; and Mr. Bowman believes that the number of fibers remains through life as it was in the fœtus, and that the spare or muscular build of the individual is determined by the mold in which his body was originally cast."

The structure of the involuntary or unstriped muscles must now be considered. This form of muscular tissue most commonly occurs in the shape of flattened bands of considerable length, but of a width not exceeding thorth of an inch. These bands are translucent, and sometimes slightly granular, and are usually marked at intervals by elongated nuclei, which become much more apparent on the addition of acetic acid. Kölliker has shown that every one of these bands or fibres is either a single elongated cell (a fiber-cell) or is a fasciculus of such cells. These fibres have not usually fixed points of attachment like the striated fibres, but form continuous investments around cavities within the body-such as the intestinal canal, the bladder, the uterus, the blood-vessels, etc. or are dispersed through the substance of tissues, such as the skin, to which they impart a contractile property.

The chemical composition of ordinary (or voluntary) muscle is described in the article FLESH. It is only necessary to add that the fibrillæ, or the sarcous elements of which they are composed, consist of a substance termed SYNTONINE (q. v.), which closely resembles the fibrine or coagulating constituent of the blood; and that the same syntonine is also the main constituent of the unstriped muscles, or at all events of their fibre-cells. Like the blood-fibrine, it exists in a fluid form in the living tissue, and only coagulates or solidifies after death.

Our limited space prevents even an allusion to the arrangement and distribution of blood-vessels, nerves, and areolar-tissue in muscular structures; and we therefore pass on to the consideration of the muscles and their functions.

Muscles vary extremely in their form. In the limbs they are usually of considerable length, surrounding the bones and forming an important protection to the joints; while in the trunk, they are flattened and broad, and contribute very essentially to form the walls of the cavities which they inclose. There is unfortunately no definite rule regarding the nomenclature of muscles. Muscles derive their names (1) from their situationas the temporal, pectorals, gluteals, etc.; or (2) from their direction-as the rectus, obliquus, etc., of which there may be several pairs-as, for example, rectus femoris, rectus abdominalis, rectus capitis, etc.; or (3) from their uses-as the masseter, the various flexors, extensors; or, (4) from their shape-as the deltoid, trapezius, rhomboid, etc.; or (5) from the number of their divisions-as the biceps and triceps; or (6) from their points of attachment-as the sterno-cleido-mastoid, the genio-hyo-glossus, the sterno-thyroid, etc. In the description of a muscle we express its points of attachment by the words origin and insertion; the former being applied to the more fixed point or that towards which the motion is directed, while the latter is applied to the more movable point. The application of these terms is, however, in many cases arbitrary, as many muscles pull equally towards both attachments. Muscles opposed in action are termed antagonists, this antagonism being in most cases required by the necessity that exists for an active moving power in opposite directions. Thus, by one set of muscles, the flexors, the limbs are bent; while by a contrary set, the extensors, they are straightened. One set, termed the muscles of mastication, closes the jaws, while another set opens them; and probably every muscle in the body has its antagonists in one or more other muscles. The skeleton, which may be termed the locomotive framework, may be regarded as a series of levers, of which the fulcrum is, for the most part, in a joint-viz., at one extremity of a bone-the resistance (or weight) at the further end, and the force (or muscle) in the intermediate portion. In most cases, in order to preserve the necessary form of the body, muscles are applied at a great mechanical disadvantage as regards the exercise of their power; that is to say, a much larger force is employed than would suffice, if differently applied, to overcome the resistance. The two main sources of this disadvantage lie in the obliquity of the insertion, and consequently of the action of most muscles, and in the muscles being usually inserted very near the fulcrum. The first of these disadvantages is in many cases diminished by the enlargements of the bones at the joints. The tendons of the muscles situated above the joint are usually inserted immediately below the bony enlargement, and thus reach the bone that is to be moved in a direction somewhat approaching the perpendicular. If this enlargement did not exist, the contraction of the muscle, instead of causing the lower bone to turn upon the upper one with comparatively little loss of power, would do little more than cause the

Muscovite.

two ends of the bones to press upon each other. The second mechanical disadvantage is compensated for by gain in the extent and velocity of movement, and by the avoidance of the great inconvenience of having the muscles extended in straight lines between the ends of jointed continuous levers. Thus the bones of the forearm are bent upon the bone of the arm by the biceps muscle which arises close to the head of the latter, and is inserted at a short distance from the

elbow-joint, which acts as the fulcrum of the lever. By this arrangement, a contraction of a single inch in the muscle moves the hand, in the same time, through the extent of about twelve inches, but then the hand moves through every inch with only about the twelfth part of the power exerted by the muscle. By the junction of two or more levers in one direction, as in the different segments of the extremities, the extent and velocity of their united actions are communicated to the extreme one. Thus a blow of the fist may be made to include the force of all the muscles engaged in extending the shoulder, elbow, and wrist.

The great and characteristic property of muscular tissue-that of shortening itself in a particular direction when stimulated-is called contractility. The stimulus may be direct irritation by mechanical means, or by galvanism, or by some chemical substance, but in the living body the muscular fibres are, in most cases, made to contract by the immediate influence of the nerves distributed among them, which are consequently termed motor nerves (see NERVOUS SYSTEM), and are under the influence of the will. By an exertion of volition, we can contract more or fewer muscles at once, and to any degree, within certain limits; and as a matter of fact, there is hardly any ordinary movement performed in which several muscles are not called in play. But every voluntary muscle is also subject to other influences more powerful in their operation than the will. The movement of the features under the impulses of passion and emotion are more or less involuntary, as is shown by the very partial power the will has of restraining them, and the extreme difficulty of imitating them.

Many movements ensue involuntarily when certain impressions, which need not necessarily be attended with consciousness, are made on the surface of the body, or on any part of its interior, either by external or internal causes Such movements are termed reflex, and are noticed in the article NERVOUS SYSTEM. Our space precludes us from noticing the individual groups of muscles in the human body. Several important groups are, however, noticed under ARM, EYE, FOOT, HAND, LEG, etc.

MUSCLE SHOALS, an expansion of the Tennessee river in Alabama, about 250 m. from its mouth, where fresh-water muscles are found in great quantities, and a series of rapids make the river unnavigable for nearly 25 miles. During that distance, the river falls 100 feet.

MUSCO GEE, a co. in w. Georgia, bounded on the w. by the Chattahoochee river, which divides it from Alabama, and on the s.e. by Upatoi creek; 375 sq. m.; pop. 19,322, of which the greater part is colored. It is traversed by the south-western railroad of Georgia, and North and South railroad of Georgia. A part of the soil is very fertile; a part sandy, and portions of the county are covered with forests. The principal products are cotton and corn. The manufacturing interests are large, principally of cotton and woolen goods. Co. seat, Columbus.

MUSCOGEES-INDIANS. See CREEKS.

MUSCOVITE, the most common variety of mica (q.v.); synonyms-Muscovy glass, biaxial mica, oblique mica, potash mica, common mica, verre de Muscovie. Trimetric crystallization, usually in hemihedral forms, with a monoclinic aspect; hexagonal prisms; cleavage parallel to the base, and easily separated, forming very thin, elastic plates, which are used in stoves under the name of "isinglass," and in Russia in windows, whence called Muscovy glass. The leaves are sometimes aggregated together in stellate, plumose (plumose mica), or globular forms, or in scales, which are sometimes in masses. Hardness, 2 to 2.5; sp. gr., 2.75 to 3.1 (Dana). Luster, pearly; color, white, gray, pale green, violet-yellow, brown and dark olive-green, and the colors vary in axial and diametral directions. In transmission of light it ranges from transparent to translucent. In general terms it is a silicate of potash and alumina, containing iron, and frequently small quantities of manganese, and hydrofluoric acid (see FLUORINE). A specimen from Uto, analyzed by Rose, gave: silica, 47.50; alumina, 37.30; peroxide of iron, 3.20; peroxide of manganese, 0.90; potash, 9.60; hydrofluoric acid, 0.56; it contained also 2.63 of water. A specimen from Abborfoss contained: silica, 39.45; alumina, 9.27; peroxide of iron, 35.78; magnesia. 3.29; potash, 5.06; fluorine, 0.29: calcium, 0.32, iron, 1.45. manganese, 2.57 = 90.59 (Svauberg). Mica fuses with some difficulty before the mouth of the blow-pipe to a grayish, blebby mass; easily dissolves in borax and phosphorus salt.

Fine crystals of Muscovite occur in granite at Acworth, Grafton, and Alstead, N. H., the plates being sometimes 3 ft. across and perfectly transparent. It occurs in Massachusetts at Chesterfield with albite, and in brown, hexagonal crystals at the Middletown, Conn., feldspar quarry. At Warwick, N. Y., crystals and plates a foot and more in diameter occur in a vein of feldspar. In St. Lawrence co., 8 m. from Potsdam, on the road to Pierrepont, it occurs in plates 7 in. across; and near Saratoga in reddish brown crystals with chrysoberyl; on the Croton aqueduct, near Yonkers, in rhombic prisms, with transverse cleavage; in fine, hexagonal crystals of dark brown in Chester co., Penn.; in Philadelphia co., smoky brown, with hexagonal internal bands; and at Chestnut hill, near the Wissahickon, is a green variety. It is found in Maryland, at Jones's falls, 2 m from Baltimore, and various other localities, for which see Dana's Mineralogy.

DUCK,

MUSCOVY. See RUSSIA. MUSCOVY DUCK. See MUSK MUSCULAR FORCE, ORIGIN OF. Until the year 1866 the universally accepted theory on this subject was that of Liebig. According to him, non-nitrogenous food is consumed entirely in the production of heat; while muscular energy is due to the waste of the nitrogenous muscular tissue, and therefore of nitrogenous food. Muscular exercise should, if this were the case, cause very distinct increase in the nitrogenous excretions of the body, as well as greater elimination of non-nitrogenous substances.

But the experiments of Fick and Wislicenus, made during an ascent of the Faulhorn, led them to deny altogether the increase of excretion of nitrogen, and to come to the conclusion that the energy generated in the muscles is the result of the burning (oxida tion) of non-nitrogenous substances (fats and carbo-hydrates), and not of the burning of the albuminous constituents of muscular tissue; and they conclude that the nitrogenous constituents of muscles are rather to be regarded as forming the machine in which these substances are burned than as being themselves destroyed. (For a translation of their memoir, see Phil. Mag., June, 1866, supplementary number).

Dr. Frankland (Philosophical Magazine, Sept., 1866) arrives at the conclusion that the non-nitrogenous constituents of the food, such as starch, fat, etc., are the chief sources of the actual energy, which becomes partially transformed into muscular work. He does not, however, deny to the albuminous matters a co-operation in the production of muscular power, but he regards their chief use as being to renew the muscular tissue. The muscles are thus the source both of animal heat and of muscular energy.

Dr. Parkes, in a long and careful series of experiments (see Proceedings of the Royal Society, vols. xv., page 339; xvi., page 44; xix., page 349; and xx., page 402), examined the effect of exercise, both with a non-nitrogenous and with a nitrogencus diet. He found no marked increase, but often a diminution, of the nitrogenous substances excreted during exercise, though subsequently a slight increase took place.

Dr. Pavy, in a series of elaborate experiments recorded in the Lancet (Feb., Mar., Nov., Dec., 1876; Jan., 1877), comes to a similar conclusion. He says: "The theoretical deduction to be drawn from the investigation which has been conducted is that, although the elimination of urinary nitrogen is increased by muscular exercise, yet the increase is nothing nearly sufficient to give countenance to the proposition that the source of the power manifested in muscular action is due to the oxidation of muscular tissue."

The theory of muscular action which Dr. Parkes proposes is as follows: During action the muscles appropriate nitrogen; this act is accompanied by changes in the carbohydrates, which lead to the manifestation of mechanical force; these changes lead to effete products (lactic acid, etc.) in the muscles, which, as appears from Ranke's experiments, stop their contraction. Then ensues an action of oxygen upon the nitrogenous framework of the muscle, and a removal of the effete products of the carbo-hydrates, so that the muscle becomes again capable of appropriating nitrogen, and of acting.

But, although some such theory as this finds favor with most physiologists, and agrees with most of the experiments on the subject, it is not universally accepted.

Dr. A. Flint of New York made observations on Weston, the American pedestrian, which seemed to show that, in his case at least, the excretion of nitrogen is very distinctly increased, both during and after severe muscular work. He accordingly comes to the conclusion that "the exercise of muscular power immediately involves the destruction of a certain amount of muscular substance, of which the nitrogen excreted is a measure." That is to say, he adheres to the original view of Liebig. His experi ments are described in the Journal of Anatomy and Physiology, vol. xi., page 109; and his views are developed in the same journal, vol. xii, page 91, where also numerous references are given to other works and papers on the subject.

All observers are agreed that the amount of carbon excreted in the form of carbonic acid is very largely increased during exercise.

Besides the papers named above, the following may be consulted for a résumé of the subject: Liebig, in Pharmaceutical Journal and Transactions, 1870; Voit, in Zeitschrift für Biologie, 1870; Foster, Text-Book of Physiology, page 323.

MUSES, in the classic mythology, divinities originally included amongst the nymphs, but afterwards regarded as quite distinct from them. To them was ascribed the power of inspiring song, and poets and musicians were therefore regarded as their pupils and favorites. They were first honored among the Thracians, and as Pieria around Ólympus

was the original seat of that people, it came to be considered as the native country of the muses, who were therefore called Pierides. In the earliest period their number was three, though Homer sometimes speaks of a single muse, and once, at least, alludes to nine. This last is the number given by Hesiod in his Theogony, who also mentions their names-Clio (q.v.), Euterpe (q.v.), Thaleia (q.v.), Melpomene (q. v.), Terpsichore (q.v.), Erato, Polyhymnia (q.v.), Urania (q.v.), and Calliope (q.v.). Their origin is differently given, but the most widely spread account represented them as the daughters of Zeus and Mnemosyne. Homer speaks of them as the goddesses of song, and as dwelling on the summit of Olympus. They are also often represented as the companions of Apollo, and as singing while he played upon the lyre at the banquets of the immortals. Various legends ascribed to them victories in musical competitions, particularly over the sirens (q.v.). In the later classic times, particular provinces were assigned to them in connection with different departments of literature, science, and the fine arts; but the invocations addressed to them appear to have been, as in the case of modern writers, merely formal imitations of the early poets. Their worship among the Romans was a mere imitation of the Greeks, and never became truly national or popular. Among the places sacred to them were the wells of Aganippe and Hippocrene on Mount Helicon, and the Castalian spring on Mount Parnassus. See illus., MYTHOLOGY, Vol. X., p. 352.

MUSE'UM (Gr. mouseion), originally the name given by the ancients to a temple of the Muses, and afterwards to a building devoted to science, learning, and the fine arts. The first museum of this kind was the celebrated Alexandrian museum (see ACADEMY). After the revival of learning in Europe, the term museum was sometimes applied to the apartment in which any kind of philosophical apparatus was kept and used; but it has long been almost exclusively appropriated to collections of the monuments of antiquity and of other things interesting to the scholar and man of science. In this sense it began to be first used in Italy, and probably in the case of the famous Florentine museum, founded by Cosmo de Medici, which soon became a great and most valuable collection of antiquities. Nothing analogous to the museums of modern times existed amongst the ancients, the greatest collections of statues and paintings which were made in the houses. of wealthy Romans having been intended for splendor rather than for the promotion of art. The name soon ceased to be limited to collections of antiquities, and sculptures, and paintings; collections illustrative of natural history and other sciences now form a chief part of the treasures of many of the greatest museums, and there are museums devoted to particular branches of science. Of the museums of Britain, the British museum (q.v.) is the greatest; that of Oxford, founded in 1679, is the oldest.-The museum of the Vatican, in Rome, contains immense treasures in sculptures and paintings, and also in books and manuscripts.-The museum of the Louvre in Paris, that of St. Petersburg, and those of Dresden, Vienna, Munich, and Berlin, are amongst the greatest in the world. The usefulness of a museum depends not merely upon the amount of its treasures, but, perhaps, even in a greater degree upon their proper arrangement; and whilst great collections in the chief capitals of the world are of incalculable importance to science, its interests are also likely to be much promoted by those local museums, still unhappily not numerous, which are devoted to the illustration of all that belongs to particular and limited districts. Museums appropriated to the illustration of the industrial arts-their raw material, their machines, and their products-and of everything economically valuable, are of recent origin, but their importance is unquestionably very great. Preeminent among institutions of this kind in Britain are the South Kensington museum in London, and the Museum of science and art in Edinburgh.

MUSGRAVE, ANTHONY, b. Antigua, 1828; appointed secretary of Antigua, and afterwards administrator of Nevis. He was lieutenant governor of St. Vincent 1861-64, when he became governor of Newfoundland, where he remained till 1869, when he was appointed to the same position in British Columbia. He went out to Natal as lieutenant governor in 1871, was made governor of South Australia in 1873, of Jamaica in 1881, and of Queensland in 1883. He d. 1888.

MUSGRAVE, GEORGE WASHINGTON, D. D., LL.D.; b. Philadelphia, 1804, of north-Irish and German descent; studied at the college of New Jersey and Princeton theological seminary, but was prevented by ill health from taking a degree; entered the ministry in 1828; was pastor of the Third Presbyterian church in Baltimore in 1830-52, and of the North Tenth street church in Philadelphia in 1862-68; was corresponding secretary of the Presbyterian board of publication in 1852-53, and of the board of home missions in 1853-61, and also in 1868-70. Dr. M. was a director of Princeton seminary from 1837, and a trustee of the college of New Jersey from 1859. He was an earnest Presbyterian, a rigid Calvinist, a leader in ecclesiastical affairs, and an able debater. He d. 1882.

MUSH'ROOM, or AGARIC Agaricus, a genus of fungi, of the suborder hymonomycetes, having a hymenium of unequal plates or gills on the lower side of the pileus. The species are very numerous. Many of them are poisonous, many are edible, and some are among the most esteemed fungi. The species most esteemed in Britain is the COMMON MUSHROOM (A. campestris), a native also of most of the temperate regions both of the northern and of the southern hemisphere, and of which a very large and fine variety occurs in eastern Australia. It is found during summer and autumn (but chiefly