506 
De Gland. intest. struct. penitiori, Berol. 1835. Gurlt, 
Miiller’s Archiv, 1835, page 399,—1836, page 263. 
on Boyd, Loe ig Essay on the structure of 
m 
€ mucous membrane of the stomach, Edinb, 
1836. Krause, Miiller’s Archiv. 1837, p.8. Henle, 
Symbole ad anatomiam villorum intest. imprimis 
eorum epithelii et vasorum lacteorum, Berol. 1837, 
Hufeland’s Journal, 1838. Miiller’s Archiv. 1838, 
p- 103. Ibid. 1839. Heft iii. p. xxxi.—Heft iv. 
p- xlv. Valentin, Repertor. 1838, p. 310. Was- 
mann, De digestione nonnulla. Dissert. Inaug. 
Berol, 1839, and Froriep’s Notizen, April, 1839. 
Miiller’s Physiol by Baly, London, 1837-41, 
vol. i, 2d edit. 1839, p. 477-503, et seq. Schwann, 
Froriep’s Notiz. Feb. 1838: * Mikrosk. Unter- 
suchung. Berol. 1839. R. B, Todd, Lectures on 
the mucous membrane of the stomach and intes- 
tinal canal, Med. Gaz. 1839 and 1842. Gerber, 
General anatomy by Gulliver, Lond. 1841. A. Na- 
smyth, Three memoirs on the teeth and epithelium, 
Lond. 1841. 7' , On non-vascular animal 
tissues, Phil. Trans. 184], part ii. Martin Barry, 
On the corpuscles of the blood, Phil. Trans. 
part ii. 1840, partsi. & ii. 1841. Mandl, Anatomie 
microscopique, Paris, 1839-41. Gruby, Observ. 
microscopice, Viennz, 1841, 
( W. Bowman.) 
MUSCLE.—(Syn. Mis, Musculus, Mus- 
cular or Sarcous tissue; vulgo, Flesh, Meat.) 
This term is applied to certain fibrinous con- 
tractile organs, either elongated and fixed at 
their two extremities, or hollow and enclosing 
a cavity, which in all the higher animals are 
the seat of the power by which locomotion, 
circulation, the prehension and passage of 
food, the expulsion of many of the excretions 
and of the young, as well as other diversified 
functions, are performed. It is also used to 
denote the peculiar contractile material or 
tissue, constituting the principal and essential 
portion of such organs. This tissue is always 
arranged in the form of fibres, which in many 
minute animals occur singly, each serving the 
purpose of a perfect muscle. But they are 
usually aggregated in very great numbers, sur- 
rounded with a network of capillary vessels, and 
connected to one another by areolar tissue. The 
nervous tissue is universally associated with 
the muscular, however small may be the quan- 
tity of the latter; it is through this that the 
Stimulus to contract is ordinarily transmitted, 
and, when the mass is great, made to affect 
simultaneously many Contiguous fibres. A 
muscle is the organ resulting from the union of 
these several parts. 
Muscles are styled voluntary or involuntary, 
according as they are, or are not, subject to the 
influence of volition, and they have been usu- 
ally so classified. But, however convenient 
these terms may be in the ordinary language 
of physiology, they cannot be applied, in a 
strict sense, to the purposes of classification 
without obvious objections. Many muscles, 
especially those under the immediate domi- 
nance of reflex nervous action, (as the respi- 
ratory and sphincter muscles,) partake of both 
characters, since volition can interfere only 
temporarily with their contraction; and all 
muscles, even the most confessedly voluntary, 
are subject to emotional and instinctive influ- 
ences, in which the will has no share. The 
attempt to introduce an intermediate or mixed 
class, which has been generally sanctioned, 
MUSCLE. 
while it is an acknowledgment of the imper- 
fection of the arrangement, does not appe r te 
be ee poppers ym = ne 
or siological grounds. subjection ¢ 
pan ectlasiink to She influence of the pill | 
made the basis of classification, all muscle 
should be accounted voluntary on which 
can exercise a direct influence either in cav 
or controlling contraction, even though suc 
influence be but momentary, and capable « 
being exerted only while the stimulus exciti 
of involuntary action is in abeyance. o- 
The voluntary muscles are generally soli 
organs, while the involuntary are hollow; an 
on recurring to the minute structure of the 
respective elementary fibres, we detect ve 
striking differences between them, those of thi 
former being striped crosswise with very deli 
cate and close parallel lines, which, with som 
exceptions, are altogether absent from the la 
ter. But these exceptions are of so impo 
a kind as to demonstrate beyond doub 
there is no necessary connexion between 
minute conformation of the fibres and thei 
lation to the influence of the will. The mu 
cular coat of the esophagus often displays @ 
striped structure as far down as the stomae 
though the will has no power whatever ove 
movements ; and the heart itself is com post 
of striped fibres. As the structural difference 
between these two kinds of fibre are constan 
well-marked, and therefore easily ascertair 
and as they seem, moreover, to be rel 
varieties in the activity and mode of e: 
of their contractile power, they will be employ: 
as the ground of division in the present ¢ 
ticle. ‘ 
I shall first describe the minute anatomy 
these two kinds of elementary fibre, a 
steps of their development; and, secon 
shall advert to their mode of aggregation 
to the arrangement of the tissues found in 
nection with them. = 
a. Of the striped elementary fibres.—Th 
have received the name of Primitive Fasei 
on the erroneous supposition of their be 
bundles of finer filaments. They may be sé 
rated from the tissues associated wi 
the compound organ by a variety of me 
but as they always constitute the prince 
mass of the organ, they may be exami 
without any attempt at such separation. 
was a favourite plan with the older anator 
to obtain the fibres apart by submitting f 
to a long boiling, which destroys the textu: 
the vessels and filamentary tissue, but al 
same time considerably modifies the size, | 
and structure of the fibres. It is in general: 
requisite to take a small portion of a mt 
as fresh as possible, (but after its contrat 
has departed,) and to tear it, under water 
fine shreds, with needles. By these m 
elementary fibres will be separated f 
another, and being in parts irregularly 
and torn, can be submitted to inspectic 
a high power of the microscope, in such ace 
tion as to exhibit most of the im it poi 
their structure. Many sedulous examinati 
specimens from various sources are r% 
for the acquirement of a correct idea of | 
hen 
ae 
