506 



MUSCLE. 



De Gland, intest. struct, penitiori, Berol. 1835. Gurlt, 

 Muller's Archiv. 1835, page 399, 1836, page 263. 

 Sprott Boyd, Inaugural Essay on the structure of 

 the mucous membrane of the stomach, Edinb. 

 1836. Krause, Muller's Archiv. 1837, p. 8. Henle, 

 Symbol* ad anatomiam villorum intest. imprimis 

 eorum epithelii el vasorum lacteorum, Berol. 1837. 

 Hufeland's Journal, 1838. Muller's Archiv. 1838, 

 p. 103. Ibid. 1839. Heft iii. p. xxxi. Heft iv. 

 p. xlv. Valentin, Repertor. 1838, p. 310. Wtu- 

 mann, De digestione nonnulla. Dissert. Inaug. 

 Berol. 1839, and Froriep's Notizen, April, 1839. 

 Muller's Physiology 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, Load. 1841. A. Na- 

 smyth, Three memoirs on the teeth and epithelium, 

 Lond. 1841. Toynbee, On non-vascular animal 

 tissues, Phil. Trans. 184), part ii. Martin Barry, 

 On the corpuscles of the blood, Phil. Trans, 

 part ii. 1840, parts i. fie ii. 1841. Mandl, Anatomic 

 microscopique, Paris, 1839-41. Gruby, Observ. 

 microscopies, Viennae, 1841. 



( W. Bowman.) 



MUSCLE. (Syn. MS?, 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 lias been generally sanctioned, 



while it is an acknowledgment of the imper- 

 fection of the arrangement, does not appear to 

 be sufficiently warranted either on anatomical 

 or physiological grounds. If subjection or 

 non-subjection to the influence of the will be 

 made the basis of classification, all muscles 

 should be accounted voluntary on which this 

 can exercise a direct influence either in causing 

 or controlling contraction, even though such 

 influence be but momentary, and capable of 

 being exerted only while the stimulus excitive 

 of involuntary action is in abeyance. 



The voluntary muscles are generally solid 

 organs, while the involuntary are hollow ; and, 

 on recurring to the minute structure of their 

 respective elementary fibres, we detect very 

 striking differences between them, those of the 

 former being striped crosswise with very deli- 

 cate and close parallel lines, which, with some 

 exceptions, are altogether absent from the lat- 

 ter. But these exceptions are of so important 

 a kind as to demonstrate beyond doubt that 

 there is no necessary connexion between the 

 minute conformation of the fibres and their re- 

 lation to the influence of the will. The mus- 

 cular coat of the oesophagus often displays the 

 striped structure as far down as the stomach, 

 though the will has no power whatever over its 

 movements ; and the heart itself is composed 

 of striped fibres. As the structural differences 

 between these two kinds of fibre are constant, 

 well-marked, and therefore easily ascertained, 

 and as they seem, moreover, to be related to 

 varieties in the activity and mode of exercise 

 of their contractile power, they will be employed 

 as the ground of division in the present ar- 

 ticle. 



I shall first describe the minute anatomy of 

 these two kinds of elementary fibre, and the 

 steps of their development; and, secondly, I 

 shall advert to their mode of aggregation and 

 to the arrangement of the tissues found in con- 

 nection with them. 



a. Of the striped elementary fibres. These 

 have received the name of Primitive Fasciculi 

 on the erroneous supposition of their being 

 bundles of finer filaments. They may be sepa- 

 rated from the tissues associated with them in 

 the compound organ by a variety of means, 

 but as they always constitute the principal 

 mass of the organ, they may be examined 

 without any attempt at such separation. It 

 was a favourite plan with the older anatomists 

 to obtain the fibres apart by submitting them 

 to a long boiling, which destroys the texture of 

 the vessels and filamentary tissue, but at the 

 same time considerably modifies the size, shape, 

 and structure of the fibres. It is in general only 

 requisite to take a small portion of a muscle, 

 as fresh as possible, (but after its contractility 

 has departed,) and to tear it, under water, into 

 fine shreds, with needles. By these means the 

 elementary fibres will be separated from one 

 another, and being in parts irregularly broken, 

 and torn, can be submitted to inspection under 

 a high power of the microscope, in such a condi- 

 tion as to exhibit most of the important points in 

 their structure. Many sedulous examinations of 

 specimens from various sources are requisite 

 for the acquirement of a correct idea of their 



