Section IV.
FIBROUS BNV8L0PS3.
Ma.ny organs In tJic body are invested witli B. strong and ligamentous structure, which presents variatioas, ia its mode of connexion, and in the functions which it ftOfils.
■ BIdnt. Anot. Qen. (. li. p. 9(il.
\
STRUCTCRS OF l>EBI09TE(;U. 351
i" rt
OP TUB PBRI03TEUM. *
•' U"<>*'liIi.-illJU'
' This dense membrane, of whidi the dura mater ij- merely a pruccss, surrounds ihi* buues in all their extent, except at their articular extremities ; in thi;8e pluce»i althouji^ the perionteum is interrupted in iu connexion with the bones, it is continuous with another div-ision of the 6broua system, viz. the ligaments,
The external sur^ce is rough and flocculent ; it is coDfi founded with the sTirrounding cellukr tissue, excepting where it covers the bones of the uusal fo&ste, of ibc sinuses, and of the cavity of tlie tympanum, in which places it is united to the mucouH memlnrone ; there is also im exception in the mouth, where it is connected witi) the dense structure of the gums and pnlate. The outer surface of the dura mater is covered by (he arachnoid botJi in (lie skull and in the vertebral canal.
, The inner surface is joined to the bones by means of innumcrabie threads or prolongations, which line the canals, transmitting the nutritious vessels towards the interior. These filaments are more numerous oo the spongy cnd^ of tlie long bone^, and oil tlic surfuceb of the short ones, than in other places. They adlicre much ■ closer in the adult, and especially in old age, than in infancy.
The thickness of the periosteum is variable ; but in general it is proportioned to the vascularity of the bones, and to the age of the subject.
■' The fibres of this membrane are disposed nearly in the Stale direction as those of the hones, but in the dura mater they have a very irregular anrangomeut, and being placed over each other, they may be divided into layers, of which two arc very distinct.
3&2
AraKEUSoaBS. OR FAftCIX.
The ufics of this membrBDe are various ; in the place, it cuwni the bontis and assists in their Dutritioi by supporting the blood-vaagela ; it also serves as aj Enedium for the attachment of the ligaments, tendons, • aponeuroses, Sic., to tlie oeseous sptem ; and lastly, in - infiiocy, it unites the epiphyses to the bones.*
The perichondrium is the investing membrane of tl curtilagviif and fibro-cartilages ; it is »o itiiTular to the'' periosteum, that it la not necessary to give any detailed history of it. The principal difference relates to tbe vascularity, which is much less than in the precodioj structure. The perichondrium fiilfUs the same ftmctic with respect to the cartilages, that the periosteum doea^ to the bones; it also gives to those among the fibro«l cartilages which are thin nnd flexible, a resistance and tenacity that would otheruige be defective.
OF THE ENVBI.0PB8 OF TUB MUSCLES, OH APONfiUnOSBS.'
The term of aponeurosis has usually been applied not only to the fibrous coverings of the muscles, buli also to certain tendons, as tlnne of llie abdomen, wliicfa are distinguished by their great breadth and exlcuUi Notwithstanding the high authorities who have given tfaisi nignitiratioo to the above word, 1 believe it will be pre«i ferable, for the sake of clearnciis and distltiction, to-il restrict its application to the investing structure of the muscles ; with the meaning thus confined^ the term of a])oncuro8is may be considered as analogous with tlutt of/imcia.
Tlie muscular envelojies are of two kinds : 1. ThoMi| of the limbs. 2. Those of the trunk.
- Thi? conoMJoD of Iliii iiimnljTune wilti the piocenof ouiiiealion wdl be ooticfd In the chapler on llw osaraui lytlHD. t Src p. -11'*.
CONNEXIONS OF TUB FASCIA. 393
The aponeurosefi of the vxtremitieH are fibrous meni' bnncs, wluch eurround the musdes, and by binding togdlhiT their fibres, they prevent any displ»cement of them during the powerful contractjons to which they are subject. The muscular fascin ore usually disposed in the form of aheaths, which incase the extremities, and thus constitute a firm and resisting investment of the body, placed beneath the more yielding covering of the skin. It results from this disposition, that their external surface is connected with the subcutaneous cel- lular and adipwe tissues, and also with the superficial *ein8, lymphatics, and nerves. Their internal surface ctMi-esponds to the muscles, to which they are usually joined by a lax, cellular structure; but in some places the muscular fibres are intimately attached to the apo- neuroses, and in fact arise from them. This siorface also frequently furnishes processes or prolongations, whicli separate tlie muscles from each other, and at the same time ^ve origin to their fibres ; the«e partitioas are called mtemiusmlar ligatnenls.
The fascifie are fimdy united to the ridges and pro- icesees of the bones, and also to the annular ligaments of the hand and foot. They are composed of one or of several layers of the fibrous tissue, variously disposed ; between their fibres, openings are formed for the pas- sage of vessels and nerves. Their thickness is gene- rally proportioned to the number and power of the muscles tliey cover. The aponeuroses are almost in^-a- riiibly provided with extensor muscles ; some of which are proper to them, whilst others are only connected with them by means of expansions sent off from their tendons. Tliere are examples, of the first class, in the insertion of the tensor vaginsc femoris in the fascia lata,
2 A
364
U8B OP THE APONBtlROSKd.
find of the pnlmsrU lotigus in the faAcift pftlmam ; of the second, in the connexion of thu tendon of the bicups cubit) with the foscia of tlie fore nrra, and of the gluteus mtkximus with that of the thigh. Theiw musdes bncc the fnscife in the movements of the limbs, and thus increase the power of the musdes placed beneath tfacm.
The aponeuroses of the trunk, which are nlwajrs par- tial, cover certain muscles, and in part even stirrotind them, Tlie following are the principal ; the temporal &&cia, the deep fascia of the back, the fasciie of the neck, of the tranaversallt muscle, of the pelvis, of the perineum, &c. The superficial foscia of the abdomen, which is enumerated by some anatomists, does not strictly belong to the s)'5tem under considcmtioii ; it is composed of cellular membrane, moderately condensed.
The use of the aponeuroses is princijially to snpport and strengthen the muscular system, in which oiKce they are materially assisted by the tendinous sheaths and ligaments ; they also afford points for the origin of fibres ; lastly, they serve in some parts to protect from external pressure and injury, the vessels and nerves; and they likewise appear to favour the venous and lym- phatic circulation, and in this manner ihcy prevent vari- cose enlargement of the deep-seated veins, and effusioa into the cellular tissue.
OP THE SHBATUS OF TUB TENDONS.
Tkeas sheaths have been divided by Bichat* into two dasMB, vii. the general and the partial ; but his account of these structures is, in some of in details, imperfect.
- AnatoaueOa, Lii. p.38S.
TBKDINOUy SH8ATHS.
The fihrous slitatlis in several places consist of canals in which thu tendons are enclosed ; and, in other parts, simply forming rings and bands, they are called annulur ligaments. The fonner are tirmly attached to tlic bonea, and are lined by synovial membraues, which are also reflected on the tendons us they puss through the sheaths: this arrangement is very cndunt in the thecse of the fingers and toes. The latter consist of strong bands ex- tended over the tendons, which they retain in their situation. Some of them are divided into several pro- ceeses by 61irous septa, which are fixed to the projecting lidgGS of the neighbouring bones ; and in this manner several distinct sheaths are formed, for the transmissioD of 08 many tendons, which are lined by tlie synovial mernbreno ; there is an example of this disposition in tlie posterior uunulnr ligament of the baud, and in the luinuUr ligament of the ankle. Otliers are not sub- divided, so that the tendons arc contained in one sheath, although as they pass through it, they arc covered, and in a degree separated fi-om each other, by the syno^-ial membrane ; this is the arrangement in the anterior liga- meot of tJic hand.
These sheaths arc very thick and firm, especially ia the direction of flexion ; they are composed of distinct transverse 6bres, wtuch become thinner opposite the articulations, where indeed, as in the fingers, they some- times entirely disappear.
Tliey stT'e to maintain tiie tendons, particulariy those of the long muscles, in tlieir places during the action of the fleshy fibres, and in some instances, as in the pul- ley of the trochlearis, tlicy alter the direction of the tendons, and thus modify the movement of the parts to which they are attached. ** ^
2a 2
^f
FI8BOUS KNVEL0PE8.
P
PIBS0U8 ENTELOPEK OF CERTAIX 0SGAN8.
These ooiuist of very dense membraues, wlucb doselj bvutt, and, io miny irkstaocvs, ailhcrc to sensiul ii portant orgaos. The following structures may he vnu-'' merutwi tm belonging to this class: Uif dura malur, the tunica f>clerotica, the fibrous portion of th« pericardium, the tunica propria of the kidney, the tunica albuginea testis, the fibrous coat of the ovarium, and the siheath of the corpora cavernosa penis and clitoridis. Richat, and most of the contioental writers, also include the propcr cout of tlie spleen ; but this appears to be formed merely of condensed cellular membrane. It is doubtful if the thick coat« of the ureter, of the vas deferens, and of thi parotid duct, which pofiscss a distinct fibrous structure, ought not to be included with the preceding parts. Tlw only objection to such an arrangement i.s, that these tubes appear to possess a contractile power, which is entirely wantiog in the proper fibrous tissue.
Some of these tunics, as the dure mater, the fibrous portion of the pericardium, and the tunica albugincn testis, arc intimately united with the serous system, so &B to form fibro-aerma membranes, or, as they are called by Beclard, compound Jibrom membranes.
In some instances numerous proces.ses are sent by tbr liganKntous envelopes into the substance of the invested organs. This is seen in the tibres which penetrate into the testicle from its proper coat ; and in the ^epta pro- longed into the peuis from the sheath of the cavernous bodies. In other places there is only a connexion by cellular tis-ipe ; as in the examples of the tunica sclera^ tica and the tunica propria of the kidney ; lastly, the dura mater and the pericardium are enttrely separalcd
LIOAMBNTS.
from tfae.brajp, ap^ t^ he(u:t by the lining seroua mem- brane.
<• The fibrous envelopes are prwided for the support artd protection of the different parts to which they are nttached.
Sbction V.
'"" or THE LIGAMENTS.
These bodies, which form a very important class of thi> 6brou8 system, connect the bones, and occasionally the (ibro-cartilages, with each other. The same name has been improperly applied to many othur ports, espe- cially to the folds which are formed by the mucous, serous, and .s)-novial membranes. The true ligament* are fixed to the bones through the medium of the peri- osteum, and the linion is so remarksbly strong that a continued maceration is required to destroy it ; but in the iDfant a separation is more readily accomplished. 'w These organs may be divided into the articular and 'n6n-articuiar ; the first are placed around the different articulations, lo the formation and completion of which diey importantly contribute ; the second are unconnected iwith the joints. ' The articular ligaments are distinguished by their form into the capsular and the tunicular. The former, which mre also called filtrous cnpsuUs, consist of cylindricid bags, lined internally by the s)'novial membrane, lliey are confined lo the scapulo-humeral and ilio-fcmoral ar- 4iculations, in which they permit cvn'y species of mo- lioni in some other joints, as in the elbow and wrists
338
DlFreUENT flPKCIES OF LIGAMENTS.
there wc sj-novial capsules, strengthened by IigamentOB fibres, so OS to constitute imperfect fibrous capsules.
The fuoictUar or fascicular ligaments are extremely Dumerous ; their form is ^iirioiis, but they are usually round or flat. TTiey are for the most part placed oa, the exterior of the joints, although a few are situatcrf' in the interior. The external cords are principally placed OQ the sides, and are consequently distinguished by the name of lateral ligaments; some are placedj before and others behind the joints, and are therefor called anterior and posterior Ugiunents. AD these cordtf] are attached to the bones by their two extremities ; anil each ofthem has itsintemal surface covered by the synoris membrane, and the external by the cellular tissue. internal ligaments are only observed in the bip and knee joints ; tbey are placed within the respective cap Bules, and are surrounded by the sjTfioviftI membrane^j which is reflected on to them at their extremities.
The ligaments of the immovable articulations di< from the |H>eceding by the irregularity of their fibrcsj and by being unconnected with the synorial mcmbrnne.
The non-Rrticular ligaments are frequently attjiche< by both their ends to one bone, such are the ligament of the scapula ; others on the contrary, are conne with two or more bones ; of this species are the ischiatic and interosseous ligaments,
Tlie principal use of these organs is to secure thel different ports of the skeleton to each other ; they nl$ serve to complete the joints, and to determine the kit and extent of motion. In Rome parts of the body, in the pelvis, they form openings for the passage blood-vessels, nen*es, and muscles; and, lastly, thvy ■■ origin to muscular fibres.
TBHDONB. SKS