Meckel1812-1 Anatomy 2-8

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Meckel JF. Handbook of Pathological Anatomy (Handbuch der pathologischen Anatomie) Vol. 1. (1812) Leipzig.

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Handbook of Pathological Anatomy Volume I (1812)

Section VIII. Of the Muscular System

Article First - Of The Muscular System In The Normal State

A. General Remarks On The Muscular System

§311. The muscular system is composed of bundles of reddish soft fibres, which of all organs change their volume and form with the most facility, and thus produce motion, and occasion the displacement of the body or of some of its parts.

§ 312. All the muscles possess these characters, whatever maybe their difference in form. They may, however, be divided into two principal classes, which are founded on the connection between their activity and the actions of the intellect. These classes are the voluntary muscles, such as obey the will, and the involuntary muscles, which do not recognise its power. The muscles of these respective classes differ much m their external and internal forms ; but these differences do not exclude general considerations, as Bichat thought. (2)

§ 313. The muscles are composed of fasciculi, placed at the side of and upon each other ; and whatever the form of the muscle may be.

(1) The principal works on the general history of the muscles are ;

1. On their structure and their functions — Barclay, On muscular motiori of the human body, Edinburgh, 1808.

2. On their normalstructure — Muys, Artiflciosa musculorum fahrica, Leyden, 1741. — Prochaska, De car'ne m-usculori,. Vienna, 1778. — Prévost et Dumas, Memoire sur les phénomènes qui accompagnent la contraction de la fibre musculaire, in the Journ. de physiol, expér. vol. iii. p. 301-339. — Dutrochet, Observations sur la structure intime des systèmes nerveux et musculaire, et sur le mécanisme de la contraction chez les animaux, in his Recherches anatomiques et physiologiques sur la structure intime des animaux et des végétaux et sur leur mobilité, Paris, 1824.

3. On their abnormal structure — Schallhammer, De morbisfibrœ muscularis, Halle, 1799.

4. On their irritability — Zimmermann, De irritabilitate, Gottingen, 1751. — Haller, Mém. sur la nat. sens, et irrit. des part, du corps hum., Lausanne, 1756-1759. — Weber, De initiis ac. progr. doctr. irritab.. Halle, 1783. — Gautier, De irritabilitatis notione, naturâ et morbis. Halle, 1793. — Croonian lectures on muscular motion, in the Phil, trans., ann. 1738, 1745, 1747, 1751, 1788, 1795, 1805, 1810, 1818, etc.— J. C. A. Clarus, Der Krampf, Leipsic, 1822. — Lucæ, Grundlinien einer Physiologie der Irritabilität des menschlichen Organismus, in IMeckel, Deutches Archiv, für die Physiologie, vol. iii. p. 325. — G. Blane, On muscular motion, London, 1788 ; and in Select, dissert., London, 1822. — Barzelotti, Esame di alcuneteorie sulla causa prossima della contrazione moscolare, Sienna, 1796.— H. Mayo, Anatom, and Phiisiological commentaries, London, 1822.

5. On their mechanical laws of motion — Borelli, De motu animalium, Leyden, 1710' — Barthez, Nouvelle mécan. des mouv. de l'homme et des animaux, Carcassonne, 1798. — Roulin, Recherches sur les mouv. et les attitudes de l'homme, in the Journal de physiol, exp., vol. i. and ii.

(2) Gen. Anat. vol. ii. p. 327. “ The general muscular system very evidently forms two great divisions — . We shall not then consider them together."

its length exceeds any other dimension. These fasciculi are themselves composed of fibres, which result from an aggregation o^Jih(mcn1s, called muscular filaments. The fibres and filaments arc as long as the fasciculi, so that in them the length exceeds the other dimensions. As to the fascierdi, they do not usually extend the whole length of the muscles, but go more or less obliquely from one edge to another, or from the two edges towards the centre. The fasciculi, fibres, and filaments are angular rather than round, and at the same time, particularly the fibres and filaments, are a little flat.

The whole muscle, or its smallest filament, is composed of two substances, the muserdar substance properly so called, and an envelop of mucous tissue. 'I'he latter, which is termed the muscular sheath, [vagina muscularis,) surrounds the whole muscle and afterwards divides into large tubes, which circumscribe the fasciculi, and again divide anew iirto other smaller tubes for the fibres and filaments.

§ 314. Opinions in regard to the texture of the muscles vary much. The formation of these organs is doubtless such as has been described : but we wish to know, 1st, if there are more subdivisions than we have mentioned ; and 2d, to determine what is the formation of the finest filaments in respect to size and mechanical texture.

§ 315. In regard to the first, very artificial systems have been imagined. Muys, for instance, states, the fasciculi are composed of fibres, these of fibrils, and these last of filaments. There are three orders of fibres, the large, middle, and small. The large are composed of the middle, and these of the small fibres. There are also three classes of fibrils, the large, which unite to form the fibres ; the middle, which produce the preceding ; and the small, which are composed of filaments. Finally we have large filaments to give rise to small fibrils, and others which are smaller and of which the preceding are formed. According to this system, each fasciculus will be formed of eight subdivisions.

But this description is i.mnatural. True, we can usually divide the larger fasciculi into others which are smaller : but these can be reduced only to fibres, as the fibres can only to filaments, so that we have only three subdivisions. A fasciculus is each subdivision of a muscle visible to the naked eye, and it rarely varies in the same muscle. The fibres which form it become rdsible by boiling. They are not all of the same thickness, as some are three or four times as large as others. The filaments, on the contrary, are about the same thickness in all the muscles, so that their number in the fibres varies considerably.

Authors do not agree in estimating the thickness of the filaments They usually make it considerable. Some(l) consider it l-7th or

(1) Prévost and Dunia.9 subdivide tlie muscular fibre into three orders, callingternary fibres those which arc seen on dividing tlie muscle lengthwise ; secondary fibres, those which are obtained by dividing the ternary ; while the pt'tmary fibres are produced by mechanical alterations of the secondary. Dutrochet, to avoid confusion, proposes to confine the term muscular fibre, to tliose filiform organs which immediately compose the muscles ; to give the name of muscular fibrils, to those smaller filiform organs which are observ'cd in the intimate tissue of the muscular fibres, and the organization of which we cannot distinguish ; and finally to term those rectilinear collections of globular corpuscles observed in the intimate tissue of muscular organs, the articular muscular corpuscles. These last corpuscles correspond to the primary fibres of Prévost and Dumas. F. T.

1 8th, some(l) l-5ih, some(2) a little niote than l-3d of that of a globule of blood. Others, on the contrary,(3) suppose it even greater than that of these same globules, stating it to be l-40th of a line, wliile a globule of blood is estimated at l-3000th of a line. We can accormt for these ditferences only by supposing that the filaments have not the same size in every part, (although observers generally assert the contrary,) and by supposing that the observations have not been made upon one separate filament.

§ 316. What is the texture of the filaments ? Opinions vary perhaps more upon this subject than in regard to their volume. We may ask :

1st. Are these filaments the primary elements of form, or are they composed of other elements ? The fasciculi, fibres, and filaments often appear wrinkled transversely, and to a greater or less depth. Very different explanations have been given of this cii'cumstance. Some authors attribute it to the crispmg of the mucous tissue, the vessels, and the nerves siuTounding the muscular fibres, and which in certain circumstances, especially when boiled, contract so much from place to place, that they seem jointed, although we cannot really divide the filaments into smaller parts placed lengthwise. (4) Others consider this phenomenon as dependent on tlijs, that the filaments are strangulated from place to place and articulated, or because they are formed from an assemblage of globules or small cells, disposed longitudinally and imbedded in mucous tissue.

(1) Prochaska, loc. cit., p. 198.

(2) Autenrieth, Physiologie, v-ol. iii. p. 335.

(3) Sprengel, Institut, physiol., vol. ii. p. 125.

(4) The Wenzels have determined that each fibre is composed of round and extremely small 'corpuscles. The microscopical observations of Home and Bauer represent the muscular fibre as identical with the particles of the blood deprived of their coloring matter, the central globules of which are united in filaments. PreV'ost and Dumas have obtained the same result. These globules are united by a hard jelly or mucus, invisible from its want of color and transparency. They ai-e united, like a rosary, and form the primary fibre, while a fasciculus of such formations arranged in a similar or nearly similar manner, produces, according to them, secondary fibres. This arrangement, noticed for the first time by Leuwenhoek and Hook, has been observed also by Milne Edwards, and Dutrochet. The latter, while examining the muscular fibres of the crab, observed that they are composed of transparent fibrils arranged longitudinally, with numerous globules in their spaces: these globules are filled wibh a transparent fluid, which penetrates between their surface of fibrils, to which they seem to adhere but slightly ; for we see fibrils entirely destitute of them. The union of these fibrils and corpuscules, which he calls muscular, constitutes in his opinion the tissue of the muscular fibre, termed by him the fibro-corpuscular muscular tissue. He adds that we often perceive corpuscules without fibrils : this he terms the corpuscular muscular tissue ; his opinion is also, that very probably the fibrils, the intimate structure of which we cannot observe, are composed of this corpuscular muscular tissue, either articulated or homogeneous, but so small that it escapes the eye aided even by a microscope.

We have often observetî tliis appearance, which causes the muscular filaments to appear jointed. We have especially remarked in several insects, that the muscular fibres were contracted from part to part so regularly, that they resembled rosaries. But, we have usually recognised that in men they were united, were equally thick and slightly flattened. As to their component substance, we have never found it perfectly homogeneous ; but it always appears formed of darker globules or points, contained in a clearer medium ; these muet not be blended with those large swellings produced by coagulation.

2d. Whether these filaments are or are not formed of globules, are they hollow or solid ? This question has been answered, sometimes in one way, and sometimes in another, and always in accordance with some theory, but it is hardly susceptible of a satisfactory solution from the smallness of the objects. Most probably they are solid.(l)

§ 317. The muscles receive numerous large vessels. They are generally supplied by several arterial branches, which arise from one adjacent trunk. These vessels do not penetrate into the muscle constantly in one place, and generally they enter nearer the centre than the extremeties, and on the inside rather than on the outside. The branches at first proceed in the mucous tissue along the fasciculi ; they soon divide into an ascending and a descending branch, which continue to ramify to its smallest subdivisions ; but the smallest vessels perceptible by the microscope, are larger than the muscular filaments. (2) The several twigs, and even the branches, frequently anastomose together. The veins form two systems ; the deep seated veins, which accompany the arteries, and the superficial veins, which proceed alone. They seem to have fewer valves here than in other organs, for they are easily injected from their trunks.

Although the muscles contain large vessels, their red color does not depend on the blood which circulates in them, but on their peculiar substance. In fact ;

1st. The muscular substance is paler in the fetus, and also in reptiles and fishes, and even in the different muscles of the same animal, especially in birds, and likewise in man, when we compare the muscles of vegetative with those of animal life, although in both the vessels are the same in size and number, and even although they are larger, and the blood which they contain is redder in the former.

2d. The muscles of the cold-blooded animals have a reddish tint.

3d. This color changes in diseases, while the number and the capacity of the vessels remains the same.

41 h. The color of the muscles docs not change in those experiments, where that of the blood varies much. If respiration be suspended so as to prevent the change of venous into arterial blood, or if venous blood be injected into the arteries, the muscle preserves its reddish tint, although the color of its lilood is altered.

(1 ) This is also the opinion of Ruclolphi. Link thinks differently, because he believes the muscular fibre to be hollow. Mascagni considers it formed of small cylinders, fhc walls of whicli are composed of absorbents filled with a glutinous sutetMce.

(2) Fontana, Ueber das Vipcrngifl, p. 392.

5tli. The truth of this proposition is supported Ijy analogies drawn •from other organs.

§ 318. The nerves(l) of the muscles are also very large. Most of the nerves of the cerebral system go to these organs. Usually the large muscles receive several branches, while the small muscles have only one. The nerves of all the muscles are not of a proportional size. (§ 174.) The vessels and the nerves generally proceed together. The latter ramify like the vessels between the fasciculi and the fibres, but they cease to be visible before them, doubtless because it is impossible to fill their extreme branches, so as to make them apparent.

§319. The forms of the muscles are very different. Usually they are solid or hoUoiv, that is rolled on themselves. We may say that of all the organic systems, these parts differ the most from each other in size, although otherwise similar in structure. In fact, in no other do we observe a difference like that existing between the almost invisible muscles of the small bones of the ear, and the glutæus maximus.

§ 320. In regtu'd to chemical composition, the muscles are formed principally of fibi-S"; but they contain also albumen, gelatin, osmazome, the phosphate of soda, of ammonia, and of lime, the carbonate of lime, and an uncombincd acid, which Berzelius calls the lactic acid.

§ 321. The muscles are soft, but slightly elastic, and are easily torn after death, so that then they are but slightly solid ; but they are distinguished from all other organs by the extraordinary development of their power to change their volume and form, to contract and to extend. This property is termed irritability {irriiahilitas), and it is brought into action by agents which have no effect on other organs. It is more convenient to call it with Chaussier motility (vis muscuU insita, vis propria, agilitas, motilitas.{2)

§ 322. The particulars of muscular motion which belong to general anatomy are,

1st. The phenomena, the changes of the muscles ivhile in action.

(1) Prévost and Dumas have observed that when a nerve enters a muscle, it appears to ramify very irregularly, unless it discovers a marked tendency to direct its branches perpendicularly to the muscular fibres, although they cut them also at right ang-les. As the nerve thus ramifies, it enlarges, and its secondary fibres separate, and are distributed exactly as when deprived of their neurilemma. It then resembles a net of fibres, from which other filaments are separated and enter the muscle perpendicularly to its proper fibres. But here sometimes there are two nervous trunks parallel to the fibres of the muscle which pursue their course at some distance from each other, and mutually transmit small filaments which pass across the space of the muscle between them, intersecting it at right angles. Sometimes the trunk of the nerve is itself perpendicular tothe muscular fibres, and the filaments which it gives off expand in this direction, pass through the organ and return, forming a kind of web. In all these cases the branches of the nerves are parallel to each other, and perpendicular to the fibres of the muscle; they either return to the trunk which furnishes them, or go to anastamose with an adjacent trunk, so that they have no termination, and their relations are the same as those of the blood vessels. 'J'his last fact contradicts all previous opinions. p. 1\

(ft Some modern writers, among other, s Gruithuisen, (Anthrapologie,p. 230-23b, p. 361-364) and henhosseck {Mcdiciiiische JaJirMcchcr des Oesterreichiseken Staates^ vol. v. part. i. p. 97-122, part ii. p. 41-64), have attributed to the muscles a particular sense, called by them tlie muscular sense, or the sense of motion but this evidently depends on the general perception termed by Reil cænaesthesis. In all tlic sensations we experience during muscular action, there is nothing peculiar which may be com pared with what we experience from the senses. F. T

2d. The conditions necessary to produce this action,

§ 323. I. The phenomena of muscular action are, 1st, tlie muscle shortens or lengthens.(l) For a long time the shortening of the muscle was thought to be its only change when in an active state. When it acts, its fibres perform in a single place, or at several points at once an oscillatory motion which causes the surface to appear wrinkled . this gradually extends to all its parts, and its usual elfect is to bring the two extremities nearer each other, and to diminish the distance between the parts to which it is attached. It is difficult to determine if there takes place an alternate motion from the extremities to the centre, and from the centre to the extremities, until the latter predominates,(2) or if, as is more probable, there is only a motion from the extremities towards the centre, so that the alternative mentioned by authors is purely ap parent, and depends on a momentary contraction of the fibres which resembles a kind of oscillation. (3)

(1) Prévost and Dumas, who think that when the muscle contracts it is unaltered

cxeept in the direction of its fibres, attribute its shortening' to the sudden flexion of these fibres in a zigzag form ; in other words, to the curves of its constituent parts. They have oljserved that the summits of these curves are always situated in those parts where the nervous and muscular fibres intersect each other at right angles. Dutrochet made the same remark at the same time, but he has gone farther. Prévost and Dumas understood by contraction only the sinuous eurve of the muscular fibre considered in its mass. They have remarked that it shortens without any flexion, but they consider this shortening as the result of what Bichat calls conlractilUy nf tissue ; they have not attempted to state the mechanism by means of which this last property is brought into action. They admit in the muscular fibre a state of rest, which it assumes whenever no cause tends to lengthen it, and think that is only when the fibre is in this state in its elastic, shortening, that it becomes susceptible of curving, to shorten again, or in other words, to contract. Dutrochet's observations relate principally to this pretended state of rest. He has observed that the shortening of the fibre without any flexion depends upon the sinuous curve, upon the very minute folds of the internal tissue of this fibre, which lengthens by the unfolding of this tissue, and shortens preserving its straightness by the twisting or folding of this same internal tissue; that the fibre exists in what Prévost and Dumas improperly term a slate of rest, when this inner folding is at its maximum ; and that then only begins the development of a second phenomenon, that of the sinuous curve of the fibre; which shortens, and becomes curved by a mechanism similar to that which had efiected its shortening, while its straightness was preserved ; the difference is this, that, in the first case, the phenomenon presented by the fibre is internal, while in the latter it is external. Thus Prévost ancl Dumas considered one part of the phenomenon of muscular contraction, that which preserves the straightness of the fibre, as resulting from a simple elasticity foreign in some measure to life ; while Dutrochet represents the curve of the intimate tissue of this fibre as being as vital as its curve in the mass, since (he latter is the result of a fixed and permanent elastic state, of the elasticity with which the intimate parts of the fibre tend to preserve a certain curve which they have assumed by (he fact of the immediate cause of life, but the vital contraction of the fibre while straight results from an elastic state, which varies in degree, and even ceases to exist to a certain extent, by the fact of its relaxation. Prévost and Dumas think that it is by means of this shortening without a curve in the fibre, that the contraction of the membranous muscular organs, such as those whicli exist in the parietes of the intestinal canal, takes place, whence they conclude that (he contraction of these organs differs entirely from that of the muscles of locomotion. Dutrochet deduces on (he contrary from his obseivations, and the usual course of nature which constantly unites siinplicity and uniformity of cause, with variety and fruitfulness of result, (hat this dilference does not exist, and that in both cases contraction depends on the curve of the muscular tissue, on an elastic state the cause of which is vital. As to (he cause iiself, he dilfers from Provost and Dumas, as we shall mention hereafter, F. 4',

(2) Haller, Elem. phys. vol. iv. p. 471.

(3) Barthez, Nouv. El. dc la sc. dc l' homme ; 1706, vol. i, p. 117.

Probably also when it has contracted as much as possible, the muscle does not remain perfectly still and motionless, but this apparently permanent state, is in fact a rapid succession of small contractions and extensions.(l)

In shortening, the muscle swells and becomes thicker.

Its color when in a state of contraction and of relaxation remains the same ; it would seem then that its vessels contain as much blood in one case as in the other. Kapidiiy and power of action are both very great in the muscles. Speaking, singing, running, &c., prove the quickness with which they act. The weight they can raise, notwithstanding their force is diminished by different circumstances, proves their power to be great.

But the phenomena of muscular contraction are not the only ones which are active. The muscles possess also an active power of elongation or extension.

The phenomena which prove this proposition are, for instance, the motions of the iris, the firmness of muscles spasmodically contracted, which almost always remains even after death, while if contraction was the only vital act, it would cease at death, and relaxation would follow ; the different states of the iris which is usually closed after death, but is sometimes much dilated ; the stomach is always flabby, but often also contracted in its whole extent, or in some points only, with so much power that it is distended with difficulty, and finally, the force with which the heart dilates. All these facts are explained in a forced and unsatisfactory manner, if we suppose that elasticity alone contributes to extension.

This opinion is still more probable, because the contractions of the muscles cease or diminish from the influence of the will, and we cannot admit this effect has been produced solely by the action of the antagonist muscles, which have counterbalanced the efforts of those to which they are opposed.

But we cannot demonstrate that extension is the only vital act which the muscles perform, and that they contract simply because they are elastic ; for contraction is their first change, when they are acted on by a stimulus.

The muscles have then the power of active extension and contraction. Barthez(2) has attributed to them a third, called the fixed power of location, which consists in the power of remaining a greater or less length of time in a state of contraction; but this power is illusory, for contraction is the essence of all the phenomena on which this is founded,

§ 324. It is asked now, if when the muscle has changed its form, as has been stated, it changes also in mass and volume, that is, if it loses in thickness as much as it gains in length, and in case the loss is real, in what manner the change in mass or volume is effected ?

(1) ^'^^mnierdatn, ßibl. nat., p. 845. — Roger, De perpétua ßbr. musc, palp , — Woollaston, Croonian lecture, in the Phil.trans., 1810.

(2) Nouv. Clemens de la sc. de l'homme, 1806, vol. i. p. 131.

The muscles may augment or diminish in mass. Each of these two theories has its supporters.

Glisson, (1) Goddard, (2) Swammerdam, (3) and Erman,(4) bring forward the following experiments in support of the hypothesis, that when the muscle contracts it diminishes in volume. They take a hollow muscle, for instance, the heart of a I'rog : it is inflated, tied, and then introduced into a syringe, terminating in a narrow canal, and containing a colored liquid. The liquid lowers during the contractions of the muscle, and on the contrary rises when they cease. The heart of the frog, filled with blood, and torn from the body of the animal, becomes smaller during contractions, and larger when it is dilated. The same phenomena present themselves, but less sensibly, when a heart is deprived of blood, and without a ligature is introduced into the pipe. But in these experiments made on hollow organs, it might happen also that the cavity only experienced this alternate enlargement and contraction, or that the fluid contained was compressed or expanded.

Other experiments have been made to arrive at the same results with the solid muscles, either with some of these single organs, or with entire limbs. A muscle is introduced into a tube, and to its nerve is attached a small silver wire, which passes out through an opening in the cork, or the nerve is preserved sufficiently long to pass out of the tube. Now if the nerve be irritated directly, or by a metallic conductor, the fluid is depressed when the muscle is convulsed. But fronii the avowal of Swammerdam, the level of the water does not often vary in this experiment, and the change which sometimes occurs may be satisfactorily explained by the attraction exerted upon the liquid by the silver wire, or by the nerve.

The experiments with entire limbs are : a man plunges his arm into a large funnel-shaped tube ; the orifice is completely closed, filled with water, and the arm is moved, the level of the water is depressed during the motion, and rises when the arm is at rest. But these phenomena do not prove what the experimenters intended in making them ; for the size of the limb ought to diminish, because the veins are empty, and blood is expelled from them by the action of the muscles. Besides, the contraction of some muscles is attended with the relaxation of others, so that it is always doubtful whether the diminution in size is owing to one or the other of these two states. On the other hand, the level of the liquid did not vary in a vessel filled with water, into which the half of the body of an eel had been plunged, and made to execute the most lively motions. (5) The same phenomenon has been observed when the experiment has been repeated with the lower portion of the body of frogs.(6)

tl) Opp. omnia, 1691, vol. iii. p. 191.

(2) Phil. Irans., vol. ii. p. 356.

(3) Bibl. nat., p. 846, 847.

(4) In the Abhandlungen der Aakadcmis âer Wissenschaften Ton Berlin, 1812, 1813, p. 155 170.

(5) G. Blane, Lecture on muscular motion, p. 253.

(6) Barzellotti, Esame di alcune moderne théorie irUorno alla eausa prossima della eonirazione muscolare, Sienna, 1796.

Neither is the increase in the size of a muscle proved by the pains which arise in the arm sun'ounded by a cord,(l) as this phenomenon only proves that the muscle which contracts becomes thicker.

As the experiments which are adduced in support of the first two opinions demonstrate nothing evidently, but far from it, and as they often furnish no result from whence we could conclude either that the muscle diminishes or increases, it remains probable at present that the change in the form of the muscle is not connected with a change in its mass. (2) But this law is not proved by the experiment in which the motion of the legs of a man, placed on the edge of a beam, do not cause his body to lean to the side of the leg which moves, (3) nor by the assertions of physiologists, who pretend that there is no alternative, because the muscle shortens in proportion as it becomes thick.(4) Experiment in fact demonstrates notliing, because certain muscles re^ lax in the proportion as others contract. The assertion supposes a demonstration of what is yet doubtful. The recent experiments of Erman(5) seem in fact to favor the hypothesis, that the muscles diminish during contraction ; for when parts of eels were put into a cylinder filled with water, and having at its upper part a glass tube, the contractions produced by a chain communicating by one pole \vith the spinal marrow, and by the other with the muscles of the part, caused the liquid to sink evidently in the tube ; and when they ceased, the liquid again ascended as much as it had sunk. One objection only can be made to this experiment, which is, that some muscles relax, while others contract ; but the structure of the fish permits us to say, if the muscles of one side of the body only are contracted, all those of the separated portion are truly contracted, and this portion may be considered as forming but one muscle.

The color of the muscles is absolutely the same in action and repose. Some think it more pale when they act, because the heart, which is transparent, when the blood it contains is emptied, is naturally more pale than when dilated and full of blood.

But as the quantity of the blood usually increases in an organ acting with more power, and as this increase of itself renders the action more energetic, we ought to presume that a muscle contains more blood when in a state of contraction, that rvhen it is at rest. Many physiologists are also of this opinion. (6) Prochaska likewise believes that when the muscle contracts, fluids flow in greater abundance between its fascicuh and its fibres, and that this greater afflux causes contraction, and obliges the fibres to assume a more tortuous direction. The volume of the muscle then really increases a little on contraction, but as its vessels are full previously, this increase is so slight, that its change is not appreciable.

(1) Hamberger, Phÿs. med., Jena, p. 581.

(2) This is the opinion also of Prévost and Dumas. By putting into the glass

larger muscular masses in order to increase the effect of a change in volume, whether real or supposed, there was no manifest alteration of the level of the small tube, whence they concluded, with Blane and Barzellotti, that if the muscle changed in the least, it was to a slight degree only. F. T.

(3) Borelli, De motu animal, vol. ii. prop. 18.

(4) Sprengel, Inslit. physiol. ; vol. ii. p. 149.

(5) Gilbert, Annalen für die Physik, vol. x. 1812, p. 1.

(6) Particularly Cowper, Stuart, and Baglivi. See Haller, El. phys. voL iv. p. 644.

The arguments adduced by Haller against this theory, viz. that the motion of the heart is involuntary, that we know not why blood should flow in a greater quantity to one muscle than to another, that the muscle is very irritable, and that the artery is irot,(l) these arguments are of no weight, for irritation of the muscle would cause a more abundant flow of blood to it, independently of the energy of the vascular system, and the relatiorrs of the muscle with the will. Besides, it is certain from experiments made with this view, that the contractions of the muscles are not at least necessarily attended with a greater afflux |)f blood, and that they do not result from this afflux, since on examining the section of a muscle with a microscope there is no liquid exuding from the wound, neither during nor after the contractions. (2) Contractions take place even when the blood is coagulated in the vessels. The quantity of this fluid has no influence upon them in any manner, and although entirely destitute of blood, they contract with as much vivacity as when the muscle contains its usual quantity. (3)

Paralysis from the ligature of the arteries has been considered as a powerful argument, that muscular contraction depends on the afflux of blood. But this paralysis does not supervene immediately, and even when it occurs soon after the ligature of the arteries, it serves to prove only that the blood is necessary to preserve the normal state of the muscle, and to maintain its fitness for contraction. We have no right to deduce from it any conclusion in respect to the cause of contraction.

§ 325. II. The conditions for the activity of the phenomena of muscular irritability are :(4)

1st. The muscle must be living. At death it loses the power of changing its form by contraction, although its elasticity continues longer, and ceases only when putrefaction commences. The life of the muscle depends upon its uniirterrupted communication with the nervous and vascular systems. When this communication has been interrupted, the muscle still preserves its irritability for sometime, even

(1) /taller, loc. cit., p. 545.

(2) Ibid. exp. 1-4.

(3) Karzellotti, loc. cit., exp. 10-12.

(4) Nasse has concluded from some experiments that the irritability of the mus cles is diminished and even destroyed by water, and has also p(dnted out the influence of this opinion on the theory of various physiolog-ical and pathological phenomena. (Deutsches Archiv, für die Physiologie, vol. ii. p. 78.) This fact had been noticed previously by Humboldt, (Ueber die gereizte Muskel-und Nervenfaser, vol. ii. p. 221, 222,) Carlisle (Philos, trans. 1805, p. 23,) and Pierson (in Bradley, Med. arid phys. journal, 1807, vol. xvii. p. 93.) It was also demonstrated by Edwards, (Sur l'asphyxie des batraciens, in the Annales de chimie et de physique, vol. v. p. 356-380,) and again brought forward in his important treatise, Dc Vinjlnen.ee des agens physiques sur la vie, Paris, 1224.) F. T,

â– wha .1 removed from the body, because it contains nerves and vessels ; this power however is soon lost.

Probably then the part taken by the nerves and their power as exerted in the contraction of muscles is merely secondary, and the relations between the nervous and the muscular systems are the same as those between the systems of the muscles and vessels, viz. the simple relations of formation and of nutrition. The contractility of the muscles is situated undoubtedly in their peculiar substance, but to call this power into action, a more active life is necessary. This is derived from the nerves and vessels with which the muscles are so liberally provided, probably for this very purpose. This view of the influence of the nerves is confirmed by the circumstance, that in many muscles, it seems to be supplied in some measure by the blood. Thus the nerves of the heart are proportionally smaller than those of the other muscles, while its blood-vessels are much larger ; and farther, the extensive surface presented by the reticulated structure of its internal face is wet with blood which is constantly rushing to it. Hence too the reason that the derangements of the nervous system do not affect all the muscles in an equal degree, and that the paralysis, and even the lesion of this system by poisons, the removal of considerable portions of it, as of the brain, the spinal marrow, &c., do not derange the motions of the heart, at least so quickly and to such a degree, as the actions of the voluntary muscles, whose nerves are proportionally larger.(l) But these lesions of the nervous system are not without their effect upon the irritabikty of the heart, and the total destruction of the central parts of this system .soon arrest its motion entirely, (2) hence these and similar phenomena cannot be considered as proving that this muscle is entirely independent of the nervous system.

But we have no right to assert with Legallois, that this difference between the heart and the voluntary muscles depends on this, that the heart receives the vivifying principle necessary to manifest its activity from the whole spinal marrow, by the sympathetic nerve.(§ 182.) But we ought certainly to explain it as we have, from the differences relative to the age at which these observations on the influence exercised by the destruction of the spinal marrow are made, for the older the animal, the more of this cord may be destroyed without a suspension of the activity of the heart. (3)

Muscular irritability has then no relation with the activity of the nerves, except by reason of the formative acts necessary for its continuance in general, and for its more energetic manifestation.

But the influence of the nervous system and the power it possesses upon the irritability of the muscles is very inferior to that of the blood. This seems to be demonstrated by the facts in the experiments made to enhghten us on this obscure point. The force and duration of the contractions Is always considerably diminished in the muscles the arteries of which have been tied, while a division of their nerves does not produce the same results. (1) But these experiments perhaps only prove tliat the influence of the nerve on the continuance of the irritability in the muscles does not depend upon its communication with the centre of the nervous system, but it possesses a sufficient power independently of this same centre, and that consequently it can exercise sufficient influence on the blood of the part submitted to the experiment.

(1) Wilson, Account of some experimens relating to some experiments of Bichat ; fn the JSdinb. med. and chir.journ. vol. v. no. 9. xiii. p. 301.

(2) Leg-allois, Expir. sur le principe de lavie^ 1812, p. 83-105.

(3) Leg-allois, loc. cit., p. 89, 90, 95, 97, 98, 101, 102.

The importance of the Idood to the exercise of muscular action is demonstrated by the deleterious influence of an anomaly in sanguification, particularly upon the irritability. This power suffers generally before all the others in the morbid states of the circulatory and the respiratory systems which renders the change of venous into arterial blood imperfect. In the same manner it is extinguished so suddenly in the bodies of those persons who die by respiring gases which are unfit for the normal formation of the arterial blood, such as the carbonic acid gas, and usually after asphyxia.

In fact we cannot demonstrate that the nervous system is not affected simultaneously in these cases, and that irritability is not extinguished by naralj^sis ; an opinion, the less improbable, inasmuch as the nervous power itself then appears to be more or less enfeebled.

2d. The living muscle must be in its normal state, not only as respects form, but its chemical composition, and its power of receiving impressions. It will not contract if it has remained inactive too long, been too much distended, if compressed or changed into fat, or if exhausted by too frequent or too violent contractions.

3d. A stimulus must act upon the muscle which must be proportional with its power of receiving impressions. (2)

§ 326. The phenomena of irritability are not the same in all muscles. They vary in regard, 1, to their duration; 2, to their extent ; 3, to their rapidity of motion; 4, to the nature of the stimulus which calls them into action. Usually the same muscles present the same phe (!) Fowler, Experiments and observations relative to the influence of the fluid lately discovered by Galvanic London, 1793.

(2) As tlie extremities of tlie nerves meet tlie nmscular fibres at right angles, Prévost and Dninas conclude that the galvanic current excited in passing over these nervous filaments causes them to approximate, and that these filaments bring with them the fasciculi of the muscles to which they are attached, which produces the folding of these fibres. Thus, according to their theory, the nerves are the only organs of contraction, and the muscular fibres are inert parts, designed only to obey the nervous filaments. Dutrochet, on the contrary, maintains, that the contraction or curve of the muscular fibre depends on the development of an elastic force which is itself caused by certain molecular phenomena, so that the muscles act as springs. He considers the muscular fibres as solids, which, from the influence of certain external or internal causes, assume either in their mass or intimate parts a curved position, attended with an elastic force which tends to cause this position lobe retained. From his view of the subject, it follows that muscular contraction is a real phenomenon of elasticity, but of .an elasticity which appears and disappears successively with the curve which attends it, so that as elasticity is, in final analysis, a phenomenon of molecular action, contraction also is found in final analysis, to depend on a certain mode of action in the molecules or the corpu.scles which compose the organized solids. One may see that this theory is directly opposite to that of Prévost and Dumas. F. T.

nomena in all individuals, and the action of the whole muscular system is broughtinto play in the same manner by the same circumstances, so that the exceptions we sometimes find are much less proper to overturn general laws, since the exact knowledge of the causes which produce them will demonstrate that they depend precisely on these laws.

§ 327. 1st. There is not a single muscle which does not possess the power of contraxting some time after the intellectual phenomena, and consequently voluntary motion have ceased, even when it has been separated from the body. The circumstances are rare where irritability is extinct in the whole muscular system of a man before one hour is elapsed : but tliis faculty is lost in some muscles much sooner than in others.

It is generally admitted that it remains longer in the involuntary than in the voluntary muscles. The following has been estabhshed as the scale of its duration in the difterent organs, viz. the heart, the intestinal canal, the stomach, the diaphragm, and the voluntary muscles ; it remaining longest m the first.(l)

But this rule is often subject to exceptions. Haller himself, to whom we owe the scale just mentioned, has frequently known irritability remain in the intestinal canal longer than in the heart. (2) Zimmermann has found it remain longer in the diaphragm, and Å’der in the other voluntary muscles. Froriep and Nysten assert that irritability disappears soonest in the bladder, the intestinal canal, the stomach, and the esophagus, and continues longer in the muscles of animal life. (3)

Some experiments might induce us to suspect that the difference in the duration of irritability depends on that of the stimulus employed : for several naturalists have found, that although the heart contracts longer than any other organ under the influence of mechanical agents, it becomes insensible to galvanism sooner than the voluntary muscles. (4) These phenomena are very remarkable, as they imply that irritability is modified by the nature and the mode of action of the natural exciting causes, in this respect, that during life the natural stimulus of the heart is also a mechanical impulse, while the muscles are excited to contract by an agent very similar to the galvanic principle, if not identical with it. This hypothesis seems more probable, as in other experiments, the voluntary muscles when they were covered by the skin, preserved in fact their power of contraction longer than the heart, even under the influence of galvanism, but still they became insensible to the action of this stimulus much sooner than this organ when they were exposed like it, and when their temperature was reduced to the same level'5) because the presence of a fluid capable of being vaporized, contributes to produce the phenomena of galvanism.

(1) Haller, Mém. sur les parties sensibles et irritables, vol. ii., p. 257.

(2) Ibid., p. 340.

(3) Voipt's Magazin, vol. vi., p. 336.

(4) Giiilio in Voigt's Magazin, vol. v., p. 161.

(5) In Voigt's Magazin, vol. vi., p. 337.

But more recent experiments made with the utmost care on man and animals seem to demonstrate that the difference in the duration of irritability does not depend on the nature of the stimulus.(l) The scale established by them is not the same as that mentioned by Haller.

According to these experiments, irritability is lost, 1st, in the left ventricle of the heart ; 2d, in the large intestines ; 3d, in the small intestines ; 4th, in the stomach ; 5th, in the bladder ; 6th, in the right ventricle, the esophagus, and the iris; 7th, in the voluntary muscles, 1st, in the muscles of the trunk ; 2nd in those of the lov/er and those of the upper extremities, and finally in the two auricles, the right auricle preserving its irritability the longest.

That irritability remains longer in the voluntary muscles, is also demonstrated by the circumstance, that water distilled from the laurel or from bitter almonds, and placed in contact with the stomach and the brain, renders the heart insensible to the most powerful stimulants in ten minutes, while the voluntary muscles move several hours after. (2)

2d. The extent of motion is not the same in all irritable parts. In general, we may admit that the irides, the lymphatic vessels, and the intestinal canal, experience the most considerable changes in their volume, for they are susceptible of dilatation and of contraction to an almost incredible extent.

3d. These parts too are extended and contracted with the greatest rapidity.

4th. The nature of the stimulus to motion is not the same for all the muscles. Thus light is the specific stimulus of the iris ; the heart contracts with more power from a mechanical irritation, and its motions continue much longer and with greater energy when the irritant acts on its internal face, than when in relation with its external face. In general, the stimuli are internal or external. The first arise from the nervous system, the others are applied directly to the muscles. The former may be termed immaterial, the latter material. All the muscles are susceptible of receiving impressions from these two orders of stimulants, but there are several immaterial agents which have no action upon certain muscles ; such as particularly the stimulus of the will, whence arises the division into the voluntary and the involuntary muscles (§312). Still the changes in the activity of the brain produce analoarous phenomena in .all muscles, even in the involuntary. The passions modify the action of all the muscles in the same manner ; anger riuickens the motions of the heart and of the intestinal canal, even without the aid of the will ; it heightens the activity and increases the power of the voluntary muscles. The opposite etfects of fright and fear are experienced also in all the muscular system.

§ 328. The degree of muscular activity is modified in m.any ways by different circumstances. Generally its power is in direct ratio with the perfection of the organization of the muscles. In fact the power of the contractions may be increased even in those muscles which are less perfectly organized and not so well nourished ; but, other things being equal, the muscle which receives more nutrition always contacts with môre power than that which is less developed. We have before spoken of the influence of the blood and the nerves upon irritability (§ 327).

(1) Nysten, /iecA. dephys. ci. dc chimie palhol., 1811, p. 321.

(2) Himly, Commeniatio dc morle, Gottingen, 1794, p. 57.

The duration of the irritability after death, or the cessation of the intellectual phenomena, depends much upon the kind of death, the state of health during life, and the circumstances in which the muscle is placed after death.

Usually irritability continues a longer time in proportion to the good health of the subject, and to the rapidity of death. In a robust man, the right auricle contracted nine hours after the head was severed from the trunk,(l) while, when the disease has lingered a long time, it is entirely extinct at the end of the first hour.(2) It disappears very soon in the bodies of those individuals who have died from chronic diseases, where the process of nutrition was affected. The diseases which pass through their periods rapidly, have no influence on the duration of irritability- so that it remains even a whole day in those patients who have died from mflammation of the limgs, aneurism of the heart, apoplexy, and even nervous fevers.

But there are certain circumstances where irritability disappears immediately, even in those who have enjoyed the best health ; as in death caused by lightning, by certain poisons, by violent blows on the abdomen, by great efforts, &c. Different external agents acting on the body, also cause it to disappear promptly after death : thus hydrogen gas, carbonic acid gas, and more especially sulphureted hydrogen gas, paralyze the muscles with which they are in contact.

§ 329. Besides the vital faculty of entering into action from the power of stimulants, the muscle possesses still another, which is not necessarily connected with life, and which may be termed with Bichat extensibility, contractility of tissue, or with Haller, dead force. It is by this property that the muscle distends itself w'hen mechanical forces act upon it. Thus the muscles of the abdomen are distended during pregnancy, in ascites, and the muscles generally by the effect of tumors which are developed in the subjacent tissues, the heart by the accumulation of blood, the bladder by that of urine, the muscular tunic of the intestine by the unnatural retention or by the abnormal development of foreign substances, as air or fœces, within it, and finally all the muscles by the action of their antagoirists.

As soon as this extending power ceases to act, the muscle returns to the volume which it possesses naturally in a state of repose, and it is not distended by a strange power. When a dead muscle is divided, if it be distended, the cut portions contract and separate. The shortening of the muscles of the stump after amputations depends on this power of contractility, whence the bones which were at first concealed in the soft parts gradually appear.

(1) Nysten, loc. cit, p. 318.

(2) Nysten, loc. cit., p. 367-383.

These phenomena do not cease till putrefaction commences. But are they not phenomena of life ? We have seen them even in muscle» which have been soaked for several hours in a strong solution of opium, and in animals killed by electricity, as also in cases where these organs have not been submitted to similar agents. Bichat divided the muscles of a limb, the nerves of which had been cut ten days previous ; contractions occurred as forcibly as in those muscles whose neives had not been divided : and farther, a certain retraction of the muscles is always observed in the amputation of a paralyzed hmb. Butwe do not consider these facts as demonstrating that the phenomena of which we treat are not the results of life ; they only prove that they are the results of a vitality much slower than that which exists when the phenomena of irritability are produced ; besides, the duration and the force of the phenomena of irritability do not differ when examined comparatively in the healthy and the paralyzed muscles of the same subject.(l) Probably all the changes in the form of the muscle depend upon the same force which only acts with more energy while the life of the nerves is not extinct, but is preserved for some time afterward, although it does not seem to us probable that the stiffness of the cadaver is a vital phenomenon of the muscles, as Nysten thinks. (2)

§ 330. The muscles are not very sensible, although they receive numerous nerves.

§331. The principal differences presented by the muscular system at different periods of life are as follows :

During the earliest periods of uterine existence this system is not distinct from the fibrous, with which it forms a whitish mucous mass.

The muscles are at first very soft, have no apparent fibrous structure, and are much paler than they are afterwards. The fibrous structure does not develop itself in them till toward the beginning of the third month, and is not visible then unless they are immersed in alcohol. From our researches it seems that the large divisions of the muscles, the fasciculi, form before the smaller ones, a remarkable phenomenon, because we observe also in the animals of the inferior classes, that the final subdivisions of the muscles in which length predominates are proportionally and even absolutely larger than in the superior animals, and we see only globules or small points in the centre of those large fasciculi into which the muscle is divided. They are also thinner and more feeble. The heart alone is an exception to this rule ; for it is proportionally much larger in the early than in the subsequent periods of life.

It follows, from the great difference in the respective proportions of the regions of the body, that the same muscles have not at all times the same proportional volume in regard to each other or to the whole body ; those of the upper half of the body, of the head, the neck, and

(1) Nysten, loc. cit., p. 369.

(2) Loc. cit., p. 384-420.

Üie back, are much more developed than those of the lower extremities. Thus, for instance, some small muscles of the neck are much larger than the glutæus maximus, which finally exceeds all others m volume.

The loose part of the tendons is aheady proportionally as long and as strong as it is afterwards, but these organs are less apparent and less developed in the interior of the muscles.

According to some writers, the muscles of the fetus are less irritable than those of the adult ; and the degree of facility Avith which they contract, and the duration of contractions is much less, the nearer the fetus is to the period of its formation. But these assertions are contradicted by several facts :

1st. By the greater tenacity of life in the fetus and the newly bom animal, and the entirely opposite phenomena that mitability presents in similar animals, as the cold-blooded and the hibernating animals during their period of hibernation.

2d. By the general law, that the power and degree of effort with which muscles are endoAved during life, is usually in an inverse ratio to the facility Avith which irritability is called into action and to its duration, so that the neAvly bom animal resists longer and more easily the action of cold,(l) of the irresphable gases and anomalies in respiration. (2) Experiments carefully made have conAinced us, times Avithout number, that irritability remains after death in the neAvly born animal longer at least than in the adult. We ha\'e further found no trace of it at the end of an hour and thirty minutes in an old hamster, while the muscle of a hamster killed immediately after birth contracted eight hours after death by merely touching it. Irritability Avas also extinct in an hour and forty-five minutes in an old rabbit, Avhile it remained tAvo hours and thirty minutes in a rabbit three days old. We have almost always found its duration equally long in the newly born animal ; often longer, rarely shorter.

The contractions ahvays appeared to us to be made Avith more energy in the young than in the old animal. In fact, in the latter we even perceived that slight convulsions only took place, Avhile in the other the muscles ahvays shortened sufficiently to produce for a long time a sensible motion in the limb to Avhich they belonged.

Some time after birth the muscles become redder and stronger, but they remain for a long time round, soft, and Avith more of gelatin than of fibrin. It is only Avhen the groAvth is finished, that they become thick, angular, have more cohesion, more sohdity, that the red color is Avell marked, and that they act Avith all their power. They acquire these qualities more perfectly, as the subject enjoys better health, and they are more exercised. Their redness, as well as their cohesion and force, gradually dimmish, while, on the contrary, they become harder. Their motions are less extensive and less certain.

(1) W. Alexander, in Physiological and experimental essay on the effect of opium on the tiring system, in the Memoirs of the Manchester Society, vol. i., London, 1815, p. 85.

(2) Here we refer to a multitude of facts proving that young animals have perished less quickly under water and in the irrespirable gases : that newly born infants who have been immersed for several days, have been taken out alive ; and that the absence, the obliteration, or the contraction of the pulmonary artery has been supported without inconvenience, or at least with slight trouble, for Aveeks, months, and even years.

§ 332. The muscles present also differences dependent on the sex. Other things being equal, they are rounder and feebler, less solid and less vigorous in the female than in the male. We cannot, in the actual state of our knowledge, resolve even probably the question if there are differences relative to the races of men. However, it is possible that the anomahes which degrade us to the class of animals are more common in the inferior than in the superior races.

II. OF THE MUSCLES OP ANIMAL LIFE.

§ 333. The muscles of vegetative and those of animal life differ so essentially in all points, that, notwithstanding the general considerations into which we have entered in regard to the muscular system in general, it is indispensable to study the two series separately. We commence with the muscles of animal life.

§ 334. The muscles of animal hfe form a great part of the mass of the body, in fact nearly as much as all the other organs united. They are generally inserted around the bones and represent the forces which move these levers. They are particularly numerous and powerful in the extremities. Their formation is more or less confined in all parts where the principal functions of life are developed, that is, in the cranium, the abdomen, and the chest.

§ 335. These muscles form sohd masses, the fasciculi of which, having a straight direction, attach themselves by their two extremities to certain parts of the fibrous system, the tendons, by means of which they adhere to the periosteum which unites them to the bones : at least this is their usual arrangement. It is seldom that a muscle is not attached to a bone, or that it is inserted by one extremity only, and that its fasciculi by folding on themselves give origin to rings. Most of the sphincters, the orbicularis palpebrarum, the orbicularis oris, the sphincter ani, and the constrictores pharyngis do not adhere to the solid parts on which they act ; they take a point of support from them. The muscles which are attached to the bones by only one extremity, and which are designed to move the soft parts only, are found principally in the face, in the buccal cavity, and in the organs of generation. The annular muscles offer no appearance of tendinous structure, or at least present it only in those narrow points where they unite to the adjacent solid parts, or in those where they arise from the bones, and never in the places where they are continuous with those soft parts which they put in motion.

§ 336. The tendons are always much thinner than the muscular substance. The muscular and tendinous substances never separate suddenly, but we see them alternating together constantly for a greater or less extent. When the tendon is broad but short, it almost always sends upon the two faces of the muscle, and between its fasciculi small bands which gradually grow thinner and thinner : when it is long and narrow, it plunges between the muscular fibres in the form of a pyramid which gradually diminishes in thickness. The relation between the tendon and the muscle vaiies much. Some very large muscles have small tendons, as the glutæus maximus, while in others, as the palmaris longus, the soleus, &c., the tendon is much larger than the muscle.

§ 337. Generally the tendons are found only at the two extremities of the muscles, and they may be considered as their integral parts. The central fleshy portion of a muscle is called its helly {venter) ; we term the upper tendon, or in general the tendon attached to the most fixed point, the head {caput) , and the opposite extremity the tail {cauda) of the muscle. We term the fixed point {Punctum adhesionis, P. fixum) that to which the head is attached ; while the opposite point is termed the movable point {Punctum insertionis, P. mobile.) The muscle usually contracts towards the former. The muscles are almost always fixed by an upper and a lower tendon to two bones, one of which is more movable than the other. In the rarest cases,

1st. They are attached to the bones by one of their extremities only, the other being fixed on thfe soft parts, either that they may unite by this extremity with other muscles which act in an opposite direction, as is seen in the muscles of the anus and most of those of the genital organs, or, as in many muscles which pass upon the capsules of the joints, that they may be attached to other organs which they are designed to move.

2d. Their two extremities are loose, and when they contract they move only the skm situated upon them, and to which they adhere intimately, as for instance the platysma myoides muscle.

But it sometimes happens that we find tendons in one or several parts of the extent of the muscle which then is divided into several bellies. We usually find only one of these intermediate tendons, termed tendinous intersections {intersectio tendinia.) The muscles which present this arrangement are called digastric {biventres, digastrici.) Such are seen in the lower jaw, in the neck, and nucha, as the biventer maxilla, infierioris, the biventer cervicis, the complexus cervicis, the sterno-hyoideus, and the omo-hyoideus.

The recti muscles of the abdomen present several tendinous intersections, which are sometimes four in number. These intersections usually extend the breadth of the muscle, but sometimes, (as the upper one of the rectus muscle) they occupy only a part of it. They are almost always short in proportion to the length of the muscle, while their breadth equals that of the muscle. The dividing tendon of the digastricus is an exception to tlris rule.

These tendinous intersections, in fact, divide one muscle into several. They furnish several fixed points, towards which the fibres contract, and between which they can extend.

This arrangement then increases the contractile power of the muscle and its force of resistance, no fibre of which has an extent equal to its whole length. Hence why tendinous intersections are found particularly in those muscles which are thin and long in proportion to their other dimensions. Generally they do not change the direction of motion ; they however produce this change in the digastricus, the anterior and posterior bellies being united at an obtuse angle, by means of an intermediate tendon which is itself attached to the hyoid bone.

§ 338. Generally, many muscles act in the same direction, and produce the same change in the parts they move, and almost always contract simultaneously; hence they are called congenitals. Others act in opposite directions, and are called antagonists (antagonistce) . The first occupy the same region, are attached to almost the same points, and are placed more or less internally or externally, above or below, at the side of, or over each other. The antagonists are situated in opposite regions. All the motions of the different parts of the body may be referred to two, whether they are removed from or approach each other. One part receding from another approaches a third. These two effects are produced by the same muscles, but the different motions receive other names, according as the synonymous parts placed at the side of or opposite to each other are approximated or separated, or according as the parts of a whole which move in the same direction, but which, although united, are still movable on each other, experience a similar change in their respective situations.!

The first is abduction and adduction, produced by the abductor and the adductor muscles ; the second, flexion and extension, performed by the flexor and the extensor muscles. Abduction and extension do not essentially differ, since the result of both is to displace, in the same or nearly the same direction, two parts which at first are situated near or at the side of each other, as are for instance two synonymous limbs, the fingers of the same hand, or the toes of the same foot, and which in the second case, succeed from above downward, as the different divisions of a limb. Adduction and flexion are also the same phenomena at bottom, since both diminish the distance between adjacent parts, and establish a difference in the direction of parts which are united. In both cases, the faces of the part which changes its form preserve the same relative situation, because the same points of its circumference continue to face or to be opposite to each other, although they are moved from or towards each other. But there is a second kind of motion, in which the part turns around its axis, so as to present successively to the adjacent parts different points of its circumference. This is called rotation, and comprises two kinds : rotation imoard, and rotation outward, according as parts at the side of each other are approximated or separated ; hence a third kind of antagonist muscles, rotators inicard and rotators outward. These motions are rarely executed by a single muscle. The motion of a part in a given direction results almost always from the contraction of several congenital muscles ; hence we have, at least in parts of any magnitude, several flexors and extensors, several adductors and abductors, several rotators inward and rotators outward.

§ 339. The antagonist muscles, and using this denomination in its most general sense, the flexors and the extensors, difter not only in the characters which divide the muscles into several sections, but also in other dilferent circumstances, so that we may consider these two classes as the most important.

Their principal distinctive characters are,

1st. The flexors, generally speaking, are stronger than the exten6ors.(l ) Hence the limbs are more or less flexed when the will ceases to act, or when in a state of entire freedom, in paralysis, in sleep, in the softening of the bones, in subjects where the muscular system is debilitated. The flexors are attached to the bones which they move, farther from the centre of motion, than the extensors are : their direction is less parallel to that of the bones, so that their insertion takes place at a more obtuse angle, and is consequently more favorable. This angle enlarges as the muscle acts, on the contrary it decreases when the extensors contract. The nerves of the flexor muscles are larger than those of the extensors.

2d. A difference is said to exist between the extensor and the flexor muscles, in regard to their excitability ; that they contract only under the influence of one pole of the galvanic chain, and this pole differs for each class of muscles. (2) Thus it is asserted that the flexors contract only when the silver pole is in contact with the central extremity of the nerve, and the zinc pole with its muscular extremity, while the contrary is the case with the extensors, and that both remain still when the poles are reversed.

Still the experiments adduced in support of this proposition do not seem to establish its truth, and are well explained by the greater power of the flexor muscles, so that Ritter's law does not differ from it. At least it is not correct to say, that the flexor and the extensor muscles contract only in the circumstances which have been mentioned, for even when these circumstances are unfavorable, the greater force of the flexor muscles allows them to contract sensibly, while the extensors do not contract.

§ 340. The external form of the muscles varies much, 1st, in regard to their complexity. Many, and almost all, arise by a single head, and terminate by a single ^ail fixed to a single point; these are the simple muscles {musculi simplices) : others divide at one of their extremities into several bellies ; these are the compound muscles {muscidi compositi). The division exists sometimes at the movable extremity, as in the common flexors and the common extensors of the fingers and of the toes, the muscles of the abdomen, those of the back, &c. ; and sometimes at the opposite extremity, as in the biceps flexor cubiti, the biceps femovis, the extensors of the fore-arm and of the leg, &c. The result of the first, arrangement is that a simultaneous motion is impressed upon different parts W the same muscle. In the second kind, 1st,, the effect is increased ; 2d, when all the different bellies act, the motion produced by them is modified ; as, for instance, the leg is at once extended and drawn outward or inward ; finally, it follows that when the muscle acts in a direction opposite to what is usual, that is, when its bellies contract towards the most movable point, several parts are put in motion at the same time.

(1) Richerand, in the Mém. de la soc. méd. d'émulation, vol. iii., p. 161, 1799. — Eiém. de physiol., vol. ii., p. 213.

(2) Ritter, Beytrage zur nähern Kenntnissdes Galvanismus, Jena, 1805, vol. ii. pt. 3, 4.no.îi,p. 65.367.

Among the simple muscles are some which in some measure form the transition from the simple to the compound muscles. In fact there are several which, although arising by a single belly, and terminating by a single tail, are still composed of a greater or less number of smaller muscles, the fibres of which are extended in different directions, and are inserted into the coinmon tendon by small tendons : such are the deltoïdes and the subscapularis muscles.

As to the compound muscles, those which are the least so consist in two layers of fibres, terminating by a more or less acute angle in a common tendon situated between them. These are called the penniform muscles {musculi pennaii) . The rectus femoris anticus and the flexor pollicis longus are examples of this arrangement.

Another kind of compound muscles comprehends those of two or more bellies, which we have mentioned before (§ 337).

In the most simple muscles the fasciculi have exactly the same direction. But the direction, and the relation between the length of the fasciculi and the filaments with the length of the muscle, are not the same in all the simple muscles. Sometimes the direction of the fibres agrees with that of the whole muscle and of its tendon. In this case the length of the muscular fibres is the same as that of the whole muscle, and it is straight. This is seen in the sartorius and in the biceps flexor cubiti. Tiiis arrangement is rare. The direction of the fasciculi more commonly differs from that of the whole mass, and they descend more or less obliquely from one of the two tendons between which the belly exists to the other. We do not consider here if, as in the semi-penniform muscles {musciili semipennali, pennaii simplices), for instance in the flexors of the hand and of the foot, of the fingers and of the toes, one of the tendons, usually the upper, be attached to the bone all its length and all that of the muscle ; qr if, fixed by a point only at its upper extremity, and descending along the belly to the fibres to which it gives rise, it be loose in all its extent, as is seen in the semi-membranosus muscle. In both cases most of the muscular mass is placed on both sides between two tendons. In the first case, however, the direction of the fibres of the upper tendon is the same as that of the muscular fibres, while in the second case it is different.

§ 341. The forms of the muscles, in regard to the proportion of the three dimensions, differ much from each other, giving rise to a division of the muscles iirto the long, the broad, and the short.

§ 342. The long muscles are found principally in the extremities, and are more or less cylindrical. Usually their tendons are large, and often much longer than their fleshy portion. Sometimes, however, the contrary is the case : thus, the tendons of the lumbricales are very short. In their course they often pass over several bones placed after one another. They form several layers, of which the superficial are the longest, and the deep muscles the shortest ; usually, these last are not extended except between two adjacent bones. ThuSj for instance, the biceps cubiti is longer than the brachialis internus ; it extends from the scapula to the fore-arm, while the latter reaches only from the humerus to the fore-arm. It is among these muscles that the division into several bellies and the insertion by several tendons are the most frequent and apparent. They are even, especially at their upper part, so closely united in some regions, particularly the fore-arm, either by the aponeuroses which are extended over them, or because the fibres of one are inserted into the tendon of another, that they cannot be separated except by cutting them. Usually they are more bulging in the centre than at their extremities, because their fibres almost always extend obliquely fi'om the upper to the lower tendon, so that their extremities do not contain all their fasciculi, but only the upper and the lower, while in the centre we find not only all the central but also a part of the upper and of the lower fasciculi.

§ 343. The broad muscles are usually thin ; they are found around the cavities of which they alone constitute the parietes, at least in great part, or which they cover, and of which they take the form. Among the first are classed the broad muscles of the abdomen, and among the second, several muscles of the cranium, the frontal muscle, the temporal muscle, and most of the sphincters. Generally these muscles preserve a uniform breadth and thickness in all their course. They are usually simple ; they never terminate in long tendons, but in slips {dentationes), which attach them to différent parts. In some parts, as the chest and the abdomen, the broad muscles are placed over each other, and are somewhat alike in form and size ; sometimes the broad cover the long muscles, as in the back.

There are muscles which very evidently make the transition from the broad to the long muscles, either because they unite the two forms m all their extent, or because they are broad in one point and elongated in another. Among the former are the sterno-hyoideus, the thj'rohyoideus, and the recti muscles of the abdomen ; among the second, the pectoralis major muscle and the latissimus dorsi muscle, which are narrower at then extremities, but at the same time increase very much in thickness.

§ 343. The short muscles are usually as thick as they are broad and long. They are generally triangular or square, and are undoubtedly the strongest of all, since none contain a greater number of fibres in a given space. They are found principally in the points where great force must be employed, because the general arrangement of the parts is unfavorable to their motions ; as in the temporo-maxillary artidilation, in the hip-joint, in the vertebral column, and even partially in the hand and the foot. The glutæus maximus muscle and the deltoid muscle make the transition from this to the preceding class, as the muscles of the hand and of the foot lead to the first.

§ 345. In regard to texture, the muscles of animal life appear formed of fasciculi and of fibres, which are situated close to each other, but do not interlace. Their fibres generally extend from one tendon to another ; sometimes, however, they disappear sooner, and we are then unable to demonstrate that they are blended with the adjacent parts. Mucous tissue is very abundant in these muscles, and it is often so loose that it makes a compound muscle of a simple one, because it divides it into several heads, which are implanted in a common tendon, and which are united by a large layer of mucous tissue, as is seen in the pectoralis major muscle. The mucous tissue usually exists more abundantly in the broad muscles ; hence their fasciculi are less compact than those of the other muscles. Almost all the nerves of these muscles arise from the brain and the spinal marrow only ; and even where there are filaments of the great sympathetic nerve, as in the neck, nerves are received also from the nervous system of animal life. The nerves often come from remote parts of the spinal marrow, although the great sympathetic nerve is the nearest source, as is seen in the diaphragm. The muscular system of animal life generally receives more nerves but fewer blood-vessels than that of vegetative life.

§ 346. The muscles are the powers which act upon the bones or analogous organs, to remove weights. The bones are levers, and usually simple levers of the second class, in which the power, viz. the muscle, is placed between the point of rest, one extremity of the bone, and the resistance, the other extremity of the bone with the parts which are attached to it. The arrangement is not the same in all ; but generally speaking, it is in a manner more or less unfavorable ; so that to produce their effect, the muscles have to employ a force greater than would be required if the relation between the power and the resistance were more favorable. Hence the muscular force is very considerable. This law may be called the law of Borelli, because until the time of this physiologist, the contrary opinion was admitted, and it was maintained that the muscles are arranged to raise the heaviest burdens by employing the least possible force.

The circumstances which demonstrate that in general the arrangement of the muscles is unfavorable ar,e,

1st. They are inserted near the fixed point. Almost all the muscles are attached nearer to this point than to the resistance. When then a weight is raised which is farther from the resistance than the insertion of the muscle, power employed by the muscle is greater in proportion to the difference between its distance from the fixed point and the distance between the latter and the weight : it is always greater than the weight of the burden.

2d. The obliquity of the muscles in regard to the hones, or of the muscidar fibres in regard to the tendon. Few muscles are attached to the bones at right angles, the most favorable of all for the employment of force ; most of them are inserted at very acute angles. On the other hand, in almost all the muscles the direction of the fleshy fibres varies more or less from that of the tendinous fibres. In regard to the first circumstance, the loss of force is greater in proportion to the obliquity of the angle of the insertion of the muscle in the bone ; as to the second, the loss which results from it is proportioned to tire obliquity of the muscular with the tendinous fibres.

3d. The resistance which the muscle opposes to the hone on which it takes its fixed point. This bone, in fact, tends to extend it as much as does the weight raised by its efibrt, because the muscle contracts from its two extremities towards its ceirtre.

4th. The resistance of the antagonists over %vhich it must prevail.

5th. The friction caused hy the parts which surround the muscle, although it is diminished by the looseness of the mucous tissue which envelops it in all parts.

But, notwithstanding all these circumstances usually unfavorable to the muscle in relation to the weight it ought to raise, there are others which diminish the loss of force occasioned by them.

Thus, the angle by which the muscle is attached to the bone is con • siderably increased,

1st. By the swelling of the extremities of the bone on which the muscle passes.

2d. By the extension of the ridges hr which they are inserted.

3d. By the formation of special small bones, which develop themselves in the substance of the tendons, at a little distance from their insertion (§ 306).

4th. By the direction that the parts give to the muscles, or only their tendons, near their termination ; they change their direction from oblique to perpendicular. It often happens that the angle of insertion of the muscle enlarges during the motion itself, and that from a very acute it becomes almost a right angle. This is observed both in the muscles which act and in their antagonists. As to the friction, it is diminished by the fat which accumulates between the muscles and between their fasciculi, and by the presence of fibrous organs, the sheaths, which give to the muscles and their tendons a determinate situation and a fixed direction.

The loss of force which necessarily results from the obliquitj? of the fibres is amply compensated by their great increase in number ; for, in equal spaces, the more oblique the direction, the more numerous are the fibres, and, other things being equal, the power of the muscle is in direct ratio with the number of its fibres.

Besides, in contracting, the oblique fibres shorten the muscle much more than the straight fibres. It requires less effort then to bring together two fixed points by oblique muscles than it does by straight muscles, more particularly as often, for instance between the ribs, two oblique muscular layers which intercross, by acting diagonally, take the place of a single straight layer. This arrangement of the force diminishes the lassitude arising from muscular motion.

For the same reason, when the muscular fibres are oblique, motion takes place more quickly than when they are straight.

Finally, when two intercrossing layers of oblique muscular fibres act on the same part, the motions admit of greater variety, since possibly the two layers contract at a time or only one of the two acts, and both employ an equal or different force.

C. Of The Muscles Of Vegetative Life

§ 347. The muscles of vegetative life differ from those of animal life.

1st. In respect to their mass. This is less, for they form but a trifling part of the organism even when we refer to them all the parts which have a slightly muscular structure.

2d. In respect to their external form. This is much more simple. They always form cavities which are lined by the internal membrane of the organs which they tend to compose. They are found in the vascular system, the digestive apparatus, the uterus, and the bladder, of which they form the muscular coat. Except in the heart, they have no appearance of tendons, because their action does not tend to displace the solid parts of the organism, but to expel fluids contained in the cavities they circumscribe. When tendons are seen, as in the heart, they are attached to parts which change their position by the contraction of the portions of the organ to which the opposite extremities are attached. The annular muscles of animal life also present something analogous, for we can always figure them as the commencement of a canal, or rather as a dilated canal, the fibres of which would pass, not behind, but over each other. But these latter, both by their situation and their functions, make the transition from the muscles of animal to those of vegetative life : for the sphincters of the mouth and anus are placed on the limit of vegetative and of animal life, and the orbicularis palpebrarum muscle is less subject to the will than the other muscles of animal life.

3d. In regard to their texture, they differ in several ways ;

а. In the general arrangement of their fasciculi, fibres, and filaments. These are not distinct and parallel to each other, as in the muscles of animal life, but interlace continually, and for this reason are much shorter than the fibres of the voluntary muscles.

б. Their fibres are arranged in several superimposed layers not only in those parts where nearly the same direction is followed, but where they proceed in opposite directions.

These layers are most generally transverse or oblique, and form rings around the cavities they circumscribe. These rings are always stronger than the fibres which extend in other directions : they are nearest each other at the orifices of the cavities and form internal layers ; they constantly surround the internal cavities, while, frequently the other layers are evident only in some parts of their circumference, as for instance in the large intestine, and are deficient in a considerable extent, as in most of the venous system. Sometimes longitudinal fibres are found without annular fibres, as in the large veins. These two directions are the most usual, and also exist together most frequently.

c. There is less of mucous tissue in the muscles of vegetative hfe.

d. Their texture presents greater differences in different parts. There is more difference in color, cohesion, and situation, between the fibres of the heart, the arteries, the veins, the intestinal canal, and even between the different parts of the intestinal canal, the uterus, and the bladder, than is found in regard to size and external form between those muscles of animal life which differ the most from each other.

The heart is very red, redder than the muscles of animal hfe, as solid as they are, but more compact, and very thick in proportion to its cavity ; its internal face is very unequal and reticulated, and it is composed of several superimposed layers. The fibres of the arteries are hard, brittle, flat, and yellowish, and all follow precisely the same direction. Those of the veins are redder, softer, and directed the contrary way, and are visible only in the large trunks.

The muscular fibres of the intestinal canal are of a pale red, and very soft.

In the esophagus and in most of the alimentary canal, we find only two layers of fibres ; in the stomach are three. Their thickness is not proportional to the size of the cavity.

The fibres of the bladder are pale and form a much more complex tissue than in the other organs.

The fibres of the uterus are very indistinct, except during pregnancy, and even then they are pale and hardly visible ; and, with the arterial fibres, are, of all we have mentioned, the most unlike the muscles of animal hfe, to which the fibres of the heart bear the greatest resemblance.

e. Have the fibres of the muscles of vegetative life more power of resistance than those of animal hfe, as Bichat asserts, because that ruptimes of the hollow muscles are rare, however greatly they may be distended, while many examples have occurred of ruptures of the voluntary muscles ? Is it a fact that the muscles of vegetative hfe are rarely ruptured, while this often occurs in those of animal hfe ? We think precisely the contrary. Bichat states that we find many instances on record of ruptures of the diaphragm, while rupture of the stomach, the intestines, and the heart, are not known. If we wish to anive at an exact result, we must not compare a muscle, which, from its situation, form, and functions, is unable to support a violent shock, with other muscles on which this cause camiot act directly ; we should consider the two systems in the same circumstances. But — will a voluntary muscle tear more readily than a muscle of vegetative hfe, when slowly and gradually distended ? We think not. The muscles of animal hfe frequently become thin membranes from the pressure of large tumors without being ruptured ; they resist the powerful efforts of their antagonists, while a mechanical obstacle not unfrequently causes the rupture of the muscles of vegetative life.

4th. In the arrangemetit of their nerves and vessels. They receive fewer nerves but more vessels than the muscles of animal life. Their nerves except those of the esophagus, the stomach, and the bladder, are derived for the most part from the great sympathetic nerve.

5th. The muscles of vegetative life have no antagonists. Their function is to contract and shorten the canals and cavities they surround. Hence the substances within these cavities are usually considered as their antagonists. The different layers of which they are composed are not opposed in action, but on the contrary by acting in concert, they execute their function better, viz. that of diminishing the size of their cavities. The action of some layers does not interfere with and prevent that of others ; a kind of opposition is, however, more or less evident between the different regions of the muscular layer of the same organ of vegetative life. Thus the fibres of the ventricles of the heart always contract alternately with those of the auricles, as those of the arteries alternate wdth those of the ventricles : the greatest activity of the fibres of the auricles is attended with the greatest degree of inaction in the ventricles, exactly as is seen between the antagonist muscles of animal life. There are regions in the intestinal canal where the antagonism is but temporary, between which are no distinct limits, and which are not marked by differences of structure, for they are adjacent portions which alternately dilate and contract to expel the substances contained in this tube.

6th. The muscles of vegetative life act, at least part of them, sooner than those of animal life. This is true, especially in regard to the heart and the alimentary canal. As certain parts, at least of the heart, preserve their irritability longer than all the other muscles, after the extinction of the mind, (§ 327,) we may say, in general, that irritability continues longest in the muscles of vegetative life, although there are some of the muscles of animal life which remain irritable longer than some of the involuntary muscles.

7th. The muscles of vegetative differ from those of animal life in the relation between them and the stimulus which causes them to act. This relation is of two kinds :

a. The muscles of which it treats are more or less influenced by the modifications of the spiritual principle. The will has rarely any influence upon many of them, as the heart,(l) and perhaps never has any if we except some cases which may be otherwise explained. Its influence on others, as the bladder and the rectum, is very feeble, and their actions as caused by the will are very slow. On the contrary, the changes which take place involuntarily in these muscles cannot be arrested by the will. Hence why their motions are not changed, or but in a slight degree, in states which are marked by a total inaction of the intellectual principle, and during which the muscles of animal life are at rest.

(1) Tliis, however is the case in an Englishman, mentioned by Cheyne, and that of Bayle, as reported by Ribes, who could at pleasure relax or suspend the motions of the heart (?) F. T.

b. The stimuli which act on them are always separated from the muscles by an intermediate substance, as in the intestinal canal and the bladder by the mucous membrane, in the vascular system by the internal membrane of the vessels, &c. But this difference is not entirely absolute, for we find an arrangement very analogous to it in the voluntary muscles, inasmuch as their nerves which are the conductors of the different changes supervening in the central parts of the nervous system, in virtue of which the muscles contract, are also separated from the proper muscular substance by the mucous tissue which envelops them.

Article Second - Of The Muscular System In The Abnormal State

§ 348. The muscular substance when once destroyed is never reproduced, and wounds of the muscles, where there is no loss of substance, heal in the same manner as those where the substance is destroyed. These two states are very similar, from the separation which the contractions of the two portions of the .muscle cause between the edges of the wound«. In both cases the opening is always a deep point,, around which tne edges of the wound in the muscle are sometimes swelled. It fills at first with a vascular, reddish, soft, and gelatinous mass, which afterwards loses its vessels and becomes yellowish white, harder, and horny, and always insensible to the action of stimulants, whatever they may be. We sometimes, but not often, find in this mass, several months after the wound, traces of irregular fibres, but slightly analogous to muscular substance, and when the muscle has been entirely divided, its portions are so completely separated that the irritation of one part causes no contraction in the other.(l) Still, however, notwithstanding this insulation, both continue to be nourished, and they do not waste, as happens to a nerve which has been cut ; doubtless because the muscles, unlike the nerves, do not form an uninterrupted organized system. A muscle which has been transversely divided and has cicatrized, is in fact changed into a double-bellied muscle, and resembles those which have tendinous intersections.

§ 349. The muscles present anomalies in form, chemical composition, and in action. We shall here examine only the first two.

(1) Kleemann, Diss. sistensquœdam circa productionem partium corporis humant, Halle, 1786, exp. ii. — Murray, Commentatio de redintegratione partium corporis humani nexu suo solutarum vel amissarum, Gottingen, 1787, exp. i-x. — Huhn, De regeneratione partium, Gottingen, 1787. — Schnell, De natura reunionis musculorum rulneratorum , Tubingen, 1804.

§ 350. Among the deviations of formation/ 1 ) which are usually pnmitive, we class :

1st. Anomaly in number. This is almost always congenital. Sometimes all the muscles of thé whole body or of a whole limb are deficient, although the other parts are formed ; but this occurs only when the whole body is incompletely developed, and particularly when its upper part is not formed and there exists in its place a gelatinous mass. In many cases of this kind some mistake may have arisen in regard to the muscles, because they are then usually very white, and an enormous quantity of liquid is found accumulated under the skin. It is more frequent that some muscles are either wholly or partially deficient, so that for instance they are not attached to the solid parts as extensively as usual. The muscles most frequently absent are those of small size, the functions of which are trivial and may be supplied more or less by others, as the palmaris brevis, the plantaris, the pyramidalis, and the zygomaticus minor muscle, and some fasciculi or heads of the flexors of the fingers or toes.

Supernumerary muscles are rarely found. (2) The enlargement and the multiplication of slips of insertion gradually leads to this anomaly, which exists in some muscles rather than in others : thus we see it often in the recti muscles of the abdomen, the small muscles of the head, the biceps femoris, and less frequently in the biceps flexor cubiti. It is not uncommon in the latissimus dorsi, the pectoral muscles, the indicator muscles, and the extensor proprius minimi digiti. Among the supernumary muscles thus developed, we distinguish the sternalis muscle, a proper extensor of the third toe, &c. We-nust here remark, that one limb resembles another in this respect, that the anterior portion of the body is regulated by the posterior, and that these anomalies almost always are analogous with the structure of some animal. (3)

2d. An unusual largeness or smallness in the size of the muscles is seldom congenital ; they commonly develop themselves accidentally. When muscles are abnormally small, it results from the want of exercise. Compression even destroys some muscles entirely. An unusual degree of power in these organs, often but not always, results from their being used. It becomes morbid only when a muscle, for instance the heart, performs its functions so powerfully as to injure the general health.

(1) Heymann, Varietates præc. corp. hum. muscul., Utrecht, 1784. — Brugnone Observations myologiques, in the Mém. de 'rurin, vol. vii. p. 157-191. — Roscnmuller, De nonnullis musc. corp. hum. varietat., Léipsic, 1804. — Gantzer, Diss. anat. muscul. variet. sistens, Berlin, 1813.

(2) Tiedemann having found the pectoralis, major and minor, the glutæi and the trapezii muscles double in the same subject, concludes, that great power in man is not always the result of exercise, but sometimes depends on the congenital redundancy of several large muscles. {Deutsches Archiv für die Physiologie.) The author of this treatise was led to form the same opinion from another example of the same kind, and he concludes from sufficient facts, that contrary to the opinion of Tiedemann, this anomaly of the muscular system happens usually on both sides at once, as Bichat has said.

(3) J. F. Meckel, De duplicitale nionstrosa, Halle, 1715, § 42.

3d. The muscles sometimes present primitive anomalies in their attachments. Not reaching then their accustomed points, they remain powerless, or act contrary to what they ought naturally.

4th. Anomalies in connection are usually accidental. They are either confined to the muscle or extend to its relations with the adjacent parts. We have already described (§348) the phenomena which attend wounds of the muscles. We not unfrequently find a rupture of whole muscles or more commonlj'- of some muscular fasciculi, an effusion of blood around the rent, and this although there is no external injury. These ruptures(l) probably depend on the spasmodic contractions which supervene in the late moments of life. But sometimes the loss of substance is consecutive to the effusion of blood. Continual pressure may also destroy some part of a muscle, and in this manner interrupt the connection which exists between it and the others.(2)

The displacements of the muscles in regard to the adjacent parts, usually result from adhesions which the organs contract after \dolent inflammation. This inflammation may also cause the adhesion of the muscular fasciculi to each ocher, which is accompanied with a greater or less degree of rigidity. The luxation of the muscles may also be referred to this cause. (3)

§ 351. Among the alterations in the texture of the muscles we must place first the anomalies they offer in their degree of cohesion ; they are sometimes extremely flabby and brittle, and again on the contrary more elastic and firmer than usual. The former state is observed in feeble men and in asthenic diseases ; the second is independent of every other morbid state, and occurs most frequently in the hollow muscles, as the bladder, and especially the heart. The color of the muscles sometimes varies from its natural shade, although their texture in other respects is not sensibly altered. Thus in certain cases the muscles are unusually pale. This state most frequently attends paralysis, brittleness, and flaccidity of the muscles. The same anomaly of color is' observed also in dropsy, where the interstices of their fasciculi are filled mth serum and not with fat. Under these circumstances the substance of the muscle ivasies considerably.

So likewise in rheumatism, which generally attacks the sheaths of the muscles, we almost always find a gelatinous fluid effused between these sheaths and the surface of the muscle.

The paleness and softness of the muscles form the transition to an altered texture of these organs which is unfrequent, and which sometimes constitutes a primitive deviation of formation in supernumerary hmbs, and sometimes supervenes to inaction of the muscles : we mean their change into fat, either preserUng their texture or losing it enthely, and finding in them celhdar tissue filled with fat.(l) All the parts of the muscles then generally become smaller than they are in the normal state. (2)

^1) J. SédiUot, Mémoire sur la rupture musculaire ; in the Mém. et Prix dé la soc. med. de Paris, 1817.

(2) Lieulaud, Hist. anat. méd., Paris, 1767, vol. ii., p. 329.

(3) J. Hausbrand, Diss. luxatîonis sic dictes muscularis refutationem sistens, Ber lin, 1814. This dislocation admitted by Poutcau, Portal, and others, can take place only when the enveloping aponeuroses are divided ; but Hausbrand has gone too far in Baying it was absolutely impossible. F. T.

The stcatomatous tumors are developed between the fasciculi of the muscles less frequently.

The accidental formation of bone(3) and the tuberculous, schirrous, or fungous formations in the muscles are still more rare.

The appearance of hydatids in the mucous tissue which separates the fasciculi of the muscles is a phenomenon a little less rare. We have found it in the voluntary and involuntary muscles, and among the last principally in the heart.

§ 352. It rarely or never happens that the muscular substance is accidentally developed. In fact, sarcoma has been placed in parallel with themuscle,(4) it has been pretended that the serous membranes,(5) and even the bones(6) have been changed into muscular substance, and finally, that this substance has been found in the ovaries. (7) But, undoubtedly in pointing out alterations of texture, the distinctive characters have been neglected to attend only to their analogies.

Article Second - Special Remarks On The Synovial Membranes

A. Of The Synovial Membranes In The Normal State

§ 367. The synovial capsules and the bursæ mucosÅ“{l) present all the essential characters of the proper serous membranes in regard to form and functions, as Munro, Gerlach, and Bichat had already remarked. But they differ in certain respects so much as to deserve to be studied separately ; and they are so similar to each other, that we had better embrace them all in a general description. They may be termed, collectively, the synovial membranes. The principal characters which belong to them all, and in which they differ from the serous membranes, are as follows ;

1st. Their relations with the adjacent parts. They are, at least generally, united to bone in a part of their circumference, and this bone is cartilaginous where they adhere. They are more closely connected with the cartilage than the serous membranes are with the parts which they cover.

2d. Their texture. It is very common to see a particular kind of corpuscles which project within their cavity. In fact these corpuscles do not exist in all the synovial membranes, nor in all the bursæ mucosæ, but they are found constantly in several. They are very vascular masses, and of course very red, especially at the end which is unattached, slightly hard, of different forms, and they are inclosed in the special folds of the membrane, while their loose extremity is almost always fringed. Those met with in the articular capsules are usually protected from all external pressure, being situated in the depressions of the bones. These latter however always press slightly upon them when they move. In some joints, as the hip-joint, there is only one, while several are found in others, as in the knee- and the elbow-joints.

These corpuscles are termed Haver's glands {glandidœ mucilaginosœ), because Havers first called the attention of anatomists to them, (2) although Cowper had already mentioned some of them. He considered their structure to be glandular, and their function to secrete synovia. Beside these bodies which project into the cavities of the articular capsules, we fiml others on their external face in the surrounding mucous tissue.

(_1) Jancke, De capsulis tendinum articularibus, Leipsic, 17.53. — Pourcroy, Si.v Mémoires pour servir à I' hist. anat. des tendons, dans lesquels on s'occupe spécialement de leurs capsules muqueuses, in Mém. de Paris, 1785-1788.— A. Monro, Description of all the bursæ muco.sœ of the human body, Kdinburph, 1788.— Koch and Eysold, De bursts tendinum mucosis, Wittenberg“, 1789. — Nurnberger and Gerlach, De bursis tendinum mucosis in capite et collo reperiundis, Wittenberg“, 1793.— Koch, De. morbis bursarum tendinum mucosarum, Leipsic, 1790. — Rosenmuller, Jccnes et descript, bursarum mucosarum corporis humant, Leipsic, 1799. — Brodie, Pathological researches respecting the diseases of the joints, in the Land. med. chir. trans., vol. iv. and V., 1813, 1814.

(1) Osteologia nova, London, 1691:

It is not probable that the glands of Havers are only masses of fat, and that they secrete synovia, although Portal(l) still maintains this opinion. The great number of vessels they receive, their situation, and the mucous fluid which exudes from them when they are compressed, do not authorize us to admit it, as there are several strong reasons against it. In fact :

a. Secretion takes place in the serous membranes, although they have no apparatus like that in the glands of Havers.

b. These bodies exist only in a few synovial membranes ; they are very rarely found in the tendinous bursæ. Synovia however is secreted every where.

c. I'lieir structure does not differ from that of ordinary mucous tissue filled with fat. They are not glandular, and although they have a considerable volume, we see no appearance of an excretory duct.

(1. We find in some parts in the serous membranes analogous prolongations which are only masses of mucous tissue filled with fat or s^rum ; such are the epiploic appendices of the colon and those of the upper extremity of the testicle.

3d. We cannot question the analogy between the articular capsules and the bursæ mucosæ, although these organs sometimes open into each other. This appears not unfrequently in the shoulder-, the hip-, and the knee-joint, and almost always occurs in the last two articulations. The adjacent bursæ mucosæ also frequently open into each ■other, and the masses of fat of the articular capsules often project into the adjacent bursæ mucosæ. It is asserted that this arrangement occurs more frequently in old subjects, so that this communication is attributed to the destruction of the parts which would otherwise serve as a barrier between the two cavities, but this theory is not correct. In all cases this communication proves that there is a resemblance between the organs, without being attended with inconvenience. Certain articular capsules perform at the same time the duties of bursæ mucosæ, as they adhere to tendons in a part of their circumference, as do for instance those of the knee and of the shoulder with the tendons of the triceps femoris and the biceps flexor cubiti.

4th. The nature of the fluid contained in these membranes is always the same, even when they communicate together. This fluid is slightly viscous, an<] its physical properties resemble the white of an egg. In man it has not yet been analyzed : but the analyses of that of the ox made by Margueron(2) and Davy (3) do not agree at all in the proportions of their constituent elements, but both state that there is a great proportion of water, a large quantity of albumen, gelatin, of the hydrochlorates, of the phosphates, and of soda.

5th. The same resemblance exists in regard to their diseases, viz. the dropsy, the thickening, and the solidifying of the substance they contain. There is one, especially the formation of cartilage, and of bone within them, which establishes a greater similarity between these organs than between the serous membianes ; for in regard to the frequency of tlris anomaly, the bursæ mucosæ are more alhed to the articular capsules than are the serous membranes.

(1) Anat. Medicale, vo). i. p. 62.

(2) Annales de Chimie, vol. xiv.

(3) Monro, Outlines of anatomy, Edinburgli, 1813, vol. i. p. 79-81.

§ 368. We have already stated the principal modifications in the form of the synovial membranes (§ 354). Most of the articular capsules form simple sacs. However there are some where the sacs are double, because an intermediate cartilage is found between the corresponding extremities of two bones ; this is seen in the temporomaxillaiy, the sterno-cla\icular, and the femoro-tibial joints, &c. We usually find only one synoHal membrane between two bones. In some parts, as for instance in the wrist, they unite a whole series of bones blended, if we maj' so speak, in a single articular surface by ligaments stretched from one to another.

§ 369 The bursæ mucosæ, with a more complex form (§ 334), may be called mucous sheaths (bursæ mucosæ vaginales), and those of CL simple {orm, vesicular bursæ (bursæ mucosæ vesiculares). A general remark in regard to both is, that they adhere in a part of their circumference to a tendon, and by the opposite face to a bone, which in this part has no cartilage, to another tendon, or finally to a fibrous ligament. On both sides they are intimately united to the organs below them, and the rest of their chcumference is surrounded by a loose and abundant cellular tissue.

The mucous sheaths are cyhnchical, and completely envelop that portion' of the tendon which they touch, and are, properly speaking, formed like the serous membranes of two sacs ; the internal sac W'hich is smaller suiTounds the tendon, while the external sac which is larger covers the adjacent parts and blends, opposite the tendon, with that portion of bone not covered by cartilage on which the tendon glides.

They are generally found in the course of long thin tendons, consequently in the extensors and flexors, especially of the fingers and toes. They surround the circumference of the tendon, but they extend a greater or less distance along these parts, hke the vesicular bursæ. The tendons of several muscles are frequently enveloped, especially in the jomts of the hand and foot, in a common sheath, which often presents as many folds and clhisions as there are tendons, so that the general sheath is more or less completely dmded into a number of special sheaths, from whence several prolongations are afterwards detached to accompany each tendon. We also find in particular sheaths small prolongations wdiich proceed ‘fi-om that part of their circumference which is adjusted to the bone, to the tendon, and are called mucous ligaments (ligamenta tendinum mucosa). These processes ' serve only to increase that of the exhaling surface. There are no fatty masses fringed upon their free extremity which float in the caiity of the mucous sheaths, although fat is often collected in their surrounding cellular tissue.

The mucous sheaths are much thimrer and more delicate than the vesicular bursæ, but they are ahvays surrounded writh dense and sohd fibrous ligaments, called tendinous sheaths, which are protected by osseous canals, while the vesicular bursæ are exposed, and only strengthened in a few instances by a fibrous substance extended on their surface.

§ 370. The vesicular bursæ are round. They never surround a tendon completely, but only cover that face of it which is turned toward the bone, and consequently form simple sacs which are more easily detached without laceration from all the parts to which they are connected. These characters apply particularly to those which are placed between two tendons. These bursæ are most generally placed between the tendons and the bones, where the former are applied directly to the latter, consequently almost always near their insertion. But they are sonretimes observed on the exterrral face of the tendon ; as happerrs for instance to the terrdons of the supraspinatus and of the infraspinatus muscles.

These vesicular bursæ are not only fixed to the bones and thé terrdons, but they are found also betweerr two bones which move orr one arrother, betweerr a synovial capsule and an apophysis of borre, between two portions of muscles, and even in the sirbstance of the tendons : the last case is perhaps only an anomaly. The third is sometimes presented between the two layers of the masseter muscle. The vesicular bursæ placed between the coracoid process of the scapula, and the clavicle is an example of the first. These bursæ are properly speaking only articular capsules; they present a peremptory argument in favor of their identity with the synovial capsules, since they demonstrate that the most simple form of the synovial nrernbranes appears also in the'articular capsules.

These bursæ are mostly simple ; sometimes however a small one exists within the cavity of a large one, as is the case between the tendon of the semi-inembranosus and the inner head of the triceps suræ. So the tendon of a muscle has usually only one vesicular bursa ; but in certain cases, as in the rnasseter muscle, the subscapularis muscle, &c., we observe several.

The vesicular bursæ are found more particularly around the large articulations surrounded with short and broad tendons, especially in the shoulder-ioint, the hip-joint, the knee-joint, and the elbow-joint. We not only find within many, as the mucous sheaths, hgamentous processes which often form a reticular tissue on their internal face ; but also we often see, as occurs in the capsules of the joints, masses of fat which float loosely and are more or less fringed on their edge.

§ 371. The synovial membranes are proportionally more extensive in the early than in the later periods of life. In age they become more dry, firm, and hard, and secrete less synovial fluid. The cellular tissue which surrounds them, as occurs in all other parts, is looser in infancy and youth, so that at this period they are more easily detached from the adjacent parts. The articular capsules and the bursæ mucosæ are not similar in regard to their number at dilferent periods of life ; for the number of the former remains always the same, if we except the accidental disappearance of some small capsules, while that of the bursæ mucosæ is always greater in young than in old persons. The communication existing between several of the synovial membranes also ditFers at different periods of hfe ; for, in the latter periods of life, the bursæ mucosæ seem to communicate, either with each other or with the synovial capsules, more frequently than in young subjects, because continued friction destroys them, directly or indirectly, in a portion of their extent.

B. Of The Synovial Membranes In The Abnormal State

§ 372. The anomalies of the synovial membranes are, 1st, their absence, which is rare, and of which only the bursae mucosæ present instances.

These bursæ are sometimes deficient in those parts where we are accustomed to find them in the normal state, and are then replaced by mucous tissue.

As to the consecutive and accidental deviations of formation, these are the lacerations which occur iirdislocations.

Sometimes we find these organs flabby and distended, either primitively or from too great an accumulation of synovia. This latter state constitutes what is termed hydrops articuli, which is never, unless accidentally, complicated with the dropsy of the serous membranes.

The synovial membranes of the joints often inflame ; ( 1) but inflammation in them is much more rare and its progress is generally slower than in the serous membranes Its effect is to increase and to change the secretion, and to thicken the membrane so that it sometimes acquires a cartilaginous hardness which extends to the surrounding mucous tissue, and is attended with the adhesion of its parietes, while its cavity is obliterated, although this latter consequence almost always results from suppuration only. When an ulcer is formed, the synovial membrane is early or late protruded.

We may, in accordance with Brodie, consider the change of the synovial membrane into a pultaceous mass of a bright brown streaked with white, as a disease pecuhar to them, which attacks neither the tendinous sheaths nor the serous membranes. This is often half an inch thick, and gradually extends to all parts of the joint, and becomes a destructive suppuration.

Chronic inflammation with suppuration, ahd the change which we have mentioned, are doubtless the most common of what are termed white swellings. In the suppurations and morbid changes described under this term, cysts are not unfrequently developed containing fluids of different kinds, a remarkable phenomenon, as it is a repetition of the tissue in which the disease is situated.

(1) Koch, De morbis bursarum tendinum mucosarum, Leipsic, 1790.

(2) Loc. cit., On cases where the synovial membrane has undergone et morbid charge of structure,

We have already mentioned the cartilaginous and osseous concretions accidentally formed in the serous membranes (§254and§ 270). (1) The knee-joint is that in which all the changes which have been made the subject of inquiry occur most frequently.

The synovial system is almost the exclusive seat of gouty concretions. These are hard, uneven, whitish substances, which are effused in the form of a fluid during or between fits of the gout. They gradually harden, and sometimes become large'; They have not always the same situation, for they are frequently found within the articular capsules and the bursae mucosæ ; they appear not unfrequently in the surrounding mucous tissue, or even between the dermis and the epidermis. They are usually composed of urate of soda. (2) It would be well to examine if the white earthy layer which sometimes forms in the place of cartilage destroyed by the gout, be not also urate of soda. (3)

§ 373. Synovial membranes are sometimes developed accidentally; this phenomenon is observed in the articular capsules, particularly,

1st. After unreduced dislocations. In this case, as a new articular cavity is formed, even when the old capsule is not torn, which almost always happens, a new capsuleis developed, which is smooth within, exhales synovia, and extends from one bone to another, and is only a little thicker, less pellucid, and less brilliant, than usual.

2d. After fractures. Here the formation of a new capsule is not a rare phenomenon. It takes place particularly when the fractured part has been moved. Hence it is observed so often after the fracture of the ribs ; then the fragments of bone do not reunite ; they become round and smooth, like the articular surfaces ; and a perfectly close capsule is developed around them, which exhales a fluid very analogous to synovia. Sometimes Havers' glands are formed in these accidental capsules. However, a new capsule is not constantly developed, and then the synovia comes from the remnant of the old membrane which has been torn. (4) Sometimes also accidental tendinous sheaths are formed ; these are more common than the abnormal articular capsules. They are real cysts, which do not ditfer from the others except in containing a fluid analogous to synovia and often thicker than it. They are called ganglio7is.{5) They are generally considered as abnormal congestions of the synovia altered in the bursæ mucosæ which existed

(1) See our Pathological Anatomy, vol. ii.

(2) Wollciston, in Horkel, Archiv für die thierische Chemie, part i. p. 147. — Fourcroy, Connais, chim., vol. x. p. 267.— Moore, Of gouty concretions or chalk-stones, in the Med. chir. Irans., vol. i. p. 112. Lambert has also found some urate of lime.

(3) S Brodie, in the Med. chir. trans., vol. iv. p. 276.

(4) Thomson, Lectures on inflammation, Edinburgh, 1813.

(5) J. Cloquet says (Note sur les ganglions, in the Archiv, gêner, de méd., vol. iv. p. 232) that the walls of these tumors are usually very thin, semi-transparent, and possess capillary blood-vessels; that the liquid they contain is usually diaphanous, sometimes very limpid, and sometimes like a reddish, thick jelly, which runs with difBculty ; finally, that we not unfrequently find in this liquid a greater or less number of foreign bodies, which float loosely, and appear to be real fibro-cartilaginous concretions. These bodies are white, elastic, and variable in figure ; some adhere by a very narrow membranous peduncle, and others are unattached. primitively ; but they are found so often in those parts where bursae mucosae do not normally exist, that they must be regarded, in many cases at least, as real accidental formations.

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Reference

Meckel JF. Handbook of Pathological Anatomy (Handbuch der pathologischen Anatomie) Vol. 1. (1812) Leipzig.

Volume 1. Table of Contents

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