Section II.
ORGANIZATION OP THE MUSCLK.S.
The peculiar tissue of the muscular system consists of. the fibre above described ; it also pussesses cellular membrane, Wood-veNseU, lymphutics, and nerves.
The cellular QR'mbrane enters VKvy largely into the composition of these ui^ns ; in fact there are but vury few parts of the body that contain a greater proportion of that substance. It hns a two-fotd disposition in the interior of the mifscle; one portion of it in\Tsting the fas- ciculi and tibres, and another intervening betwi-en them. We readily perceive, with the naked eye, that the large bundles arc covered by membrane which is rather con- densed, and it is also evident that the fibres are enclosed ' within sheaths of the same structure. With respect to the ultimate filaments, it is probable that each of them is mirromided by the cellular tissue, constituting a tube which contains the muscular pulp. The successive di-' visions of the muscle are loosely tied together by a reliculor substance, which contuinit somo fut and an albuminous fluid, destined to lubricate the component parts, and to facilitate tiieir muvumeiits. It lias been tliought, hut with little foundation, that in addition to the common fat, muscles possess a peculiar oil intended
426
ARTERIES AND VEINS.
th t**^'"* adhwfion sikI friction "between their fibrft. Tht jmriitions urc sometimes so Urge as to divide the muscle into two or more ports ; ttucfa U the septum which svparutes the cluviculur from the sternal portioD of the peotornlifi major.
In addition to the cellular sttbitance placed in the hody of the mitscle, there is a layer, which covers the extemal surfiice, so as to surround the entire or^an, and thus toMuIatc it from the neighbouring parts ; the thick- ness and density of tim layer are liable to greMt varia* tion, but in §:eneral it is most developed on the large musdeji of the trunk, where it Kcems to supply the place of f&Kcia. This common connecting medium has Tcry important uses ; in general, it fixes the muscles in their places, and by uniting the fibres together, it combines their action in a remnrknble manner ; when this sub- stimce \s removed, their contractions become vague and irregular.
The blood-vesseis of this system are very numerous, and of large size ; so that, with the exception of some of the viscera and the mucous membranes, the' are mure abundantly supplied with blood than any other organs.
'Il»e arteries usually enter nearer to the centre tban to the extremities of the muscle ; they pass, at first,-^ between the fasciculi ; each soon divides into two branches, which nm lengthwise in the inlerveoing cellu- lar tissue ; tbey subdivide into minute vessels, and ulti- mately ramify on Ibc cellular sheath of th<? muscubtr^ filament. The mode of connexion between the capiU tary arterie.i and the matter of the tilament escapes oh »er'nlion. The veins are arranged in two (mlert; accompany the arteries, and the others run superficiallj on the surbce of the muscles. The small radicles form
LYMPHATICS AKO NBBVB8.
a vascular networit, the blood of which js aft«rward.s dift- charged into larger branches, aud, at length, into the
• :Qai^)lbouriiig trunks. .'.<^ni£ lymphnUas are not so numerous as the blood- vessels ; they do not appear to extend to the musciUar fibre, but (o ariw from the intersticial cellular sub&lance.
. i; It has long been remarked thai the muscles which are
'under the control of the will, receive very lai^e and numerous nervouj^ cords; and, an Uie contrary, that the involuntary muscles, in proportion to their size, arc sparingly supplied. The nerves of volition are derived from the cerehro<»pinal axi», and those of the huUow muscles almost entirely Jrom the system of the sympa- thetic. The ocn'ous cords of the voluntary muscles as they proceed towards their distribution, form lai^, and iu some places iutricatu conununicatiuns, called pitxuaet, which have an eSKentiul influence in associating the mus- cuhu* actions. The nerves of the sympathetic also con- stitute numerous plexuses, in which they have not only communications with each other, but also with the nerves of the preceding class. This connexion, and the still more important one that exists between the cerebro- spinal system and tlie ganglions, place the muscles sup> plied from the latter source in a peculiar manner under the general influence of the nervous system. *
The filaments of the nerves in general accompany the sanguiferous vessels, particularly the arteries ; they penetrate the muscles in diiTcreut points, and, after many divisions, they become so minute as to escape all ob-scrvation. Their ultimate termination is in cunsc-
'4]uence unknown, although many attempts have been
ffp, * Philip'* Dipenini-iitwl Inquiry, jt. 101, p. 363.
438'
TSRUlNATtON OF NS&VB8.
made to detect it. Sir A. Cariisle stnlcs that the lasT subdiWsions of tiiv »c-rvou» fibrils iin! perfecUj- vinible to the tuikc'd eye, uud thut wlicre they fteon to mi, they leave a large portion of the muscular structure unoccupied by tliem. The medullar)- sulwtance, togirthcr with the enveloping membrane of the extreme fibriUn;, become soft and transparent, and thus the whole fibril being rendered indistinct, seems to be dift'usud and mingled with the subKUiacvii in which it ends. The ultimate termination is stutud to be in the reticular celiular membrane of the muscle.* Prevoat and Dumas
fhave also published more recently observations con- cerning the disposition of the nervous filaments. These physiologists difi^er iVom all otliers, by supposing that
I the filaments do not in fact terminate in the muscles, hut that they return on tlicmsclvcs, and paws either to the trunk which furnishes them, or they anastomose
'*rith some other neighbouring nerve. '"" ' '''It' te certain that the nervous fibrillie, however they may really end, are not sufficiently large or numerous to supply each individual muscular filament. It there- fore may be asked, how can thuy net ou all the fibres of the muscle? Two hypotheses hare been suggvated to explain this difficulty. Sir A. Carlisle ond Isenfiamm suppose that the celluhir tissue of the muscles, in which they conceive the nerves to terminate, acts as a con- ductor for transmitting the nerv'ous influence. Reil and others, on the contrarj-. imagine that the nerves have the sphere of their actinty extended beyond their • tennination, by what is called u nervotia atmosphere. In concluding this account of the organization of'
,-,.
Fhilw. Ttam. fix IliOS, p, 9.
CUBMICAL COHPOSITIOM.
muBcles, it is nwessary to state, that thoy ant usually oonaected by the fixtremitieit of their iibres with n ten- dinous structure ; tliis remark applii's, however, almost exclusively to the oiusclt-s of volition.
h- .1(1
Sbction in.
CHEMICAL COMPOSITION.
. It is extremely difficult, if not impossible, to make a very minute analysis of muscle, on account of the membranous matter and hlood that remain inxupurably united with it. ,
If thin slices of the muscular substance bu exposed tq the action of air, tlii.-y become dry, luml, and of a diiskjt brown colour; if too thick a portion be thus treated, it does not Aty, but in decomposed, and ussunu'K a greea and livid colour. When the muscular tibre has been macerated for a sufficient length of time in water which has been frequently changed, it becomes whitish or yel- lowish, and it is also softened and swollen ; by this plan it is obtained in as pure a state as the circimistance mentioned above will permit. Tlie water contains al- bumen, jelly, various salts, and a peculiar extractive matter, which was first discovered by Thouvenel. This substance, which vms mimed by Tbenard, ornioztnae, has a brown colour, an acrid ta.<tte, and an aromatic odour ; it is thought to be the ingredient which gives the spe- cific tlavour to the fiesh of ditfert-nt animals. ■■i, . In young animals the muscles contain a consider^le quantity of jelly, but it is doubtful if there is any of it
4S0 CHEMICAL ANALT8f0j
in the adolt, The salts that are cAntftinM Tfi tmt^^d^ flesh, or, as some think, merely in the bkwd-^-csscIs which belong to it, are principally the phosphatefi soda, ammonia, and. lime, and also the carbonate of lime. Some other saline substances have been delected by Fourcroy, Vauquclin, and Bcrzelitui. The following is the analysis of the last chemist :
Fibrin, vessels, and nerves . . 16*8
Cellular substance 1'9
Albumen 2-2
Osuuuomc, with the lactate and > . .«
hydro-chlorate of soda . . 5
Mucous matter 0*15
Pho-sphate of soda 0'9
Phoiiphate of lime, containing a l
portion of albumen ... 3
Water and loss 77" 17
100 00
Most of the strong;er acids anti 6)e catisHc alkalies dissolve tlie muscles. When nitric acid is employ^; the fibre is partly decomposed and partly dissoK-ed, while a quantity of urole, nnitod to carbonic acid, is dis- engaged. It is worthy of remark that a larger quantiti* of azote, which constitutes the basis of animal matter, is extricated Irom muscle than from any other substaheC. [ l^Ticn the action of the acid is promoted by heat, (he' muscle U quickly dtsjiolved, and the fluid a&sumcs n dc«p yellow colour. Besides other substances that are tln«^ produced, a quantity of unctuous matter is seen floating ' in tlie form of globules of oil on the surface, which be-
COLOUR NOT KSSENTIAL.
AQi.
oom«s cxincreted when the fluid cools, and being found to possess properties iDtcrmediate between those of f^f] and w«Xt it h«2t obtntoed the name of adipocire.*