CHAP. II. II. THE The Solids of the human frame, as well as of all animals, are derived from the fluids.(b) Although composed principally of one species of matter, yet they admit of great variety in their appearance. (c) They NENT MA- differ infinitely in their degrees of cohesion, from the soft and almost pulpy medulla of the brain, to the vitreous substance of the corona of the teeth.(d) TERIALS, &c. Secondly, The Solids. The principal varieties of solids, considered in relation to their form and structure, are externally the integuments (which include the skin, hair, and nails, (and internally the bones, with the ligaments and cartilages, and of joints, technically termed articulations; the muscles with their tendons; the membranes or cellular tissue (which muscles and cellular tissue with the intermixed nerves are vulgarly called Flesh; and all the various kinds of sacs and vessels, whether arteries, veins, capillary vessels, lacteals, ducts, absorbent and secernent vessels, nerves, and the whole cerebral matter. If we arrange the solids of the body with regard to their chemical composition, and to the uses which they serve in the animal economy, we may place them under five divisions, namely, 1, the osseous matter or bones; 2, the membranous or cellular tissue; 3, the muscular, 4, the adipose or fat, and 5, the cerebral or brain; and we may say in general terms, that the comparative degrees of their solidity or softness are in that order. (e) The component parts of the solids are of several kinds, varying in description and quantities in different parts. Besides, the gelatinous and glutinous parts of the solids, earth enters more or less into their composition, and is principally lime united with phosphoric acid, and whence it is commonly termed phosphate of lime. The bones possess this in the greatest abundance, particularly in advanced age. (f). The texture of the greater part of the solids consist of very minute globules, disposed together in fibres more or less parallel and continuous throughout the frame, as in the bones, muscles, tendons, ligaments, aponeurosis, (f) and in certain membranes, as the dura mater, &c. In other parts no fibres can be discovered, but the texture is peculiar, and has been termed parenchyma, and differs in va rious viscera, especially those which secrete, as in the liver and kidneys. In all these structures, whether fibrous or parenchymatous, there is inTissue, or terwoven what is properly termed membrane or cellular membrane, or of Membrane. late more commonly called cellular tissue, from its capacity to contain fluids in its minute cells,) which is quite distinct from the muscles and other parts which it surrounds, though vulgarly confounded and included with them under the general term flesh.(g) It is sometimes called mucous web, (though improperly so, because this structure neither secretes mucus nor consists of it.)(h) Indeed, the variety of names has not a little tended to perplex the student. (i) This is amongst the most important and remarkable constituents of the body, and is subject to numerous particular disorders, especially inflammation. (k) It has been described to be a net-work of a very fine membranous substance, and it is important to know that it is universally diffused over every part of the body; it not only separates various parts, as the skin from the muscles and the muscles Cellular (b) Ell. Blum. 4th edit. 23; 1 Horn. Anat. Intro. xx. (c) Hunter on Blood. (d) See note (b) supra. (f) Ell. Blum. 4th edit. 23; 1 Horn. (g) Ell. Blum. 4th edit. 26; 1 Bost. Ph. 18, and see 1 Horn. Anat. 339, as to cel lular substance; 1 Dungl. 24, 29; Jackn. Prin. Med. 19. (h) Ell. Blum. 24, 26, note A. (i) See in general, Copl. Med. Dic. tit. Cellular Tissue. (k) Ell. Blum. 4th edit. 26, note A.; and see 1 Bell. Anat. 396, as to cellular membrane; Jackn. Prin. Med. 20. from each other, but there is no minute subdivision of even a single muscle which does not exhibit cellular membrane between its fibres. (1) It serves for separation between the muscles and other parts, and to the blood and other vessels and nerves for support, and to every part it acts as the common medium of connexion.(m) It is originally derived from the lymph of the blood. Besides these utilities, it receives several kinds of fluids, the serous halitus, more commonly called exhalation, which moistens and lubricates every part. (n) Even at the risk of tautology, it is expedient here to state the observations of some of the ablest physiologists of the present day upon the subject of cellular tissue. 7500 1 300 CHAP. II. II. THE COMPO NENT MA TERIALS, &c. Cellular Dr. Edwards has recently, in his observations on the elementary struc- Dr. Edture of the body, stated the result of microscopical observations, and con- wards' accludes that the cellular substance consists of cylinders, resolved into rows count of of globules, all of the same size, (d'une excessive petitesse,) namely, thue. part of a millimetre, or about th part of an inch in diameter, and which rows of globules are separated from each other, and lie in various directions, crossing and interlacing, some of them being straight, others bent, and some twisted, forming imperfect strata, which are connected with each other by a kind of irregular net-work; and the serous as well as mucous membranes are in this respect precisely the same. The muscular fibre is composed of the like globules of the same size, but differing in this respect, that they are all composed of straight lines of globules. Tendons and the aponeuroses, and the parts of the skin, are also composed of the same sized globules, formed into lines, but differing in the direction or parallelism of the lines. The middle coat of arteries is also composed of the same kind of globules, all in the same direction, but resembling tissu fibreux. So the nerves and neryous matter are composed of lines of globules of the same size, but holding an intermediate place between membranes and muscles as to the regularity of their disposition, and having a fatty matter interspersed between the rows of globules (0) And hence he concludes, that whatever difference may be impressed on various parts, they are nevertheless all composed of the same sized minute globules, though differently disposed.(p) It is proper, however, to observe that Meckel has denied the existence of any cells. Dr. Bostock, in his excellent comprehensive treatise on physiology, ar- Dr. Bosranges the consideration of membrane or cellular tissue under three heads: tock's 1. The extent and structure of membrane; 2. The properties of membrane, view of the physical and chemical; and, 3. The different species of membrane.(7) Un- same. der the first head, he states that it is the most simple in its structure of any of the organized parts of the body; it is the most extensively dif fused, and exists in the greatest proportion. The coverings, not only of the body at large, but of each of its individual parts, both internal and external, are principally composed of membrane, and it lines all the cavities in which the different organs are situated; it constitutes the main bulk of the bones and determines their figure; the earthy matter, upon which their strength and hardness depend, being deposited in a tissue of membranous cells. Membrane also enters into the structure of muscles, not only affording them an external sheath, in which they are each of () 1 Horn. Anat. 340. (m) 1 Bost. 19. (n) Ell. Blum. 4th edit. 23 to 27. (0) Extract from 3 Bost. 273 to 277; but see variations in extract from M. Dutrochet's Elementary Structure of the Body, 3 Bost. Ph. 277; and post, 24, note (p) Phil. Trans. for 1821, p. 20, 9 vol. (2) 1 Bost. 15 to 74. CHAP. II. II. THE &c. them enclosed, but the same matter is also interposed between their fibres, separating them into bundles, to which it in like manner affords a distinct COMPO- covering, and these into still smaller bundles, until it appears at length. NENT MA to envelop each individual fibre. It also composes very nearly the whole TERIALS, bulk of the tendons by which the muscles are attached to the bones; also of the ligaments and of the cartilages. Membrane also enters very large-, ly into the composition of the hair, the nails, and other similar parts connected with the surface.(s) It likewise composes what is properly called the cellular texture, being a series of cells or interstices, which extends over a great portion of the body, fills up its intervals, and serves to unite the different parts to each other. Membranous matter is the chief ingredient in the glands, as well those belonging to the absorbent system as to the secernent. The brain is also enveloped in a covering of membrane; and it is probable that the nerves are composed of a series of fibres enclosed in membranous sheaths, analogous to those of the muscles. (1) The pouches or sacs which are formed in different parts of the body, such as the stomach and the bladder, are almost entirely composed of membrane; and what, perhaps, must be regarded as the most important of all the purposes which it serves, this substance composes the principal part of the tubes or vessels, such as the arteries and veins, with which the animal body is so plentifully furnished. (u) Membrane (vulgarly confounded with the muscles and nerves and termed flesh) exceeds in quantity all the other solids of the body taken together, and it enters, as a principal ingredient, into almost every part of the animal frame excepting the enamel of the teeth,(x) and Dr. Bostock insists that, were it possible to remove the earth from the bones, the muscular fibre, the nervous matter, and the fat from the soft parts, to empty the vessels, and to carry off the fluids generally, the size and figure of the body would remain nearly unchanged. Membrane may therefore be considered the connecting medium between the different parts of the body by which they are held together, the basis to which they are all attached, and the mould in which the particles of the other kinds of matter are deposited. (y) With respect to the structure of membrane, it is composed of a vast assemblage of lines or fibres, in their state of ultimate division, too small to be perceived by the eye, and it is stated at about th of an inch in diameter,(z) but which, by the union of a sufficient number of them, are formed either into larger visible fibres or into plates, according to the structure of the parts in which they are situated, and termed, by Haller and others, though Dr. Bostock thinks not entirely correctly so, cellular web, and it has uninterrupted continuity all over the body.(a) Insensibi lity of Secondly. With respect to the physical properties of membrane, Dr. Bostock states them to be cohesion, flexibility, extensibility, and elasticity, (the latter of which Blumenbach terms contractility, differing, however, from the moving power of muscles,) properties of the greatest importance in a system like that of the living body, in which great strength is necessary, together with lightness and a capacity for free motion, and where the parts are perpetually varying in their bulk and relative position.(b) The better opinion seems to be, that simple membrane is insensible in its healthy and natural state, but that it is liable to inflammation, and II. THE СОМРО NENT MA TERIALS, &c. and the rea that it then, sometimes, becomes severely painful.(c) This is attributed CHAP. II. to the enlargement of the bulk of the part affected by the inflammation, and the pain is generally in proportion to the difficulty with which the part admits of this extension. It has been observed that a high degree of inflammation may exist in loose cellular texture and we may be scarcely sensible of its existence, while the inflammation of the periosteum of the smallest bone, as a tooth when in its socket, or of the sclerotic coat membrane, of the eye, or of the tense membrane about the finger nail, will be almost son why intolerable. In these cases, even if the inflamed part be without nervous pain is felt filaments, which give it sensibility, still it will be found that there are when it is some branches of nerves immediately contiguous to the inflamed part, inflamed. which in consequence of the enlargement, extension, and firmness of all the neighbouring parts, are pressed upon and irritated, while the blood vessels connected with them are in a state of plethora; it is a general law of the animal economy that no cause is more powerfu! in producing pain than a certain degree of pressure upon a nerve when its sensibility is augmented by an unusual determination of blood.(d) With respect to the chemical properties of membrane or its chemical composition, and the effect of chemical re-agents upon it, Dr. Bostock observes, that the ancient doctrine, that membrane consisted of simple fibres, and that the fibre itself is composed of earthy particles cemented by gluten, is exploded, (e) and that the present doctrine is, that the basis of membranous matter is a substance which, in its chemical properties, is identical with the albumen of the egg when in a state of coagulation. Albumen naturally exists in the form of an adhesive fluid, miscible in water, but when subjected to a temperature of about 165,() it experiences a remarkable change in its physical properties; by the operation of heat it is converted into a solid, which is no longer capable of being dissolved in water; and if, after coagulation, it be gradually exposed to a higher temperature, it is reduced to a firm semi-transparent body, very similar to some of the more compact varieties of membrane.(g) But though albumen appears to be the essential part of membrane, that which gives it its general form and determines its peculiar texture, yet it probably always contains animal jelly or gelatine, and, in some cases, even much more copiously than the albumen itself.(h) Another substance is animal mucus; this is not properly soluble in water, nor does it possess the property of gelatinization, and it differs from jelly in many of its chemical relations. Animal mucus appears to be nearly related to albumen.(i) A considerable proportion of both the bulk and weight of membrane, as well as of all the other soft parts, consist of water, and it has been supposed by many eminent physiologists, that upon the relative quantity of this water and the solid matter depend many of the morbid changes of the body, as well as the natural varieties in the constitution and temperament of different individuals; and Dr. Bostock observes, that there are some facts connected with pathology and the practice of medicine, which would lead us to conceive that the elasticity, and, perhaps, even the density of some of the external parts of the body, may be influenced by being exposed to warmth and moisture.(k) (k) Id. CHAP. II. II. Tax COMPO NENT MA TERIALS, &c. Dr. Quain With respect to the ultimate chemical elements of which membrane is composed, like other animal substances, it consists essentially of oxygen, hydrogen, carbon and nitrogen or azote,() and some iron and earth and saline matters in small quantities.(m) The particles of membrane, as well as those which compose any other solid, are held together by their attraction for each other, not by any connecting medium.(n) Thirdly. With regard to the different species of membrane, Dr. Bostock describes them as, first, cellular texture; (0) and, secondly, membranes, especially so denominated, and which consist of their semi-transparent sheets or plates, which generally form the coat or covering of some other parts, and which differ from the cellular texture in the greater continuity of their structure, and are either mucous or serous or fibrous membranes.(p) Dr. Quain, in his detailed practical work on anatomy, gives a descripon Cellular tion of the different materials of which the whole frame is composed, and Tissue, and the following is the substance.(g) Certain simple substances are found generally to exist, not indeed separately, but variously combined in animal comcomposi- pounds; namely, azote, (also denominated nitrogen,)(r) carbon, hydrogen, tion of the and oxygen, which are the chief ingredients. To these are added some on the human frame. others, but in small proportions, such as phosphorus, sulphur, iron, soda, potass, and lime. Some salts, as the phosphate of lime, are found in considerable quantity, whilst others, such as the muriates of soda and potass, are sparingly diffused through a few only of the animal fluids. (8) The soft parts are made up of azote, carbon, hydrogen, and oxygen; the hard parts, especially the bones, of the lime and phosphorus. The proximate animal compounds formed from these are not very numerous. The following enumeration includes all that are sufficiently well characterized and of general occurrence; namely, gelatine, albumen, fibrine, mucus, picromel, urea, osmazome, resin, sugar, oils, and acids. The identity of the ultimate constituents of these substances will at once appear from the following tabular view, which it is unnecessary to extend beyond the first three.(t) Gelatine, or animal jelly, is an abundant ingredient, not only in the fluids, but also in the solid parts of the body, as is evident from the fact that by boiling, it can be extracted from skin, membrane, ligament, cartilage and bone. It is inodorous and tasteless, dries into glue, and is soluble in warm water, in acids, or alkalies, and becomes solid again on cooling. The solution, on cooling, forms a tremulous mass, and if the aqueous part be dissipated by heat, the remainder becomes brittle, and breaks with vitreous fracture; this is named animal glue. Gelatine is () 1 Bost. 38. Probably the power in living membrane of resisting putrefaction is owing to the small proportion of azote which it contains; Quain's El. 2d edit. 27. (m) Dr. Turner's El. Chemis. 532, ante, 14. (n) 1 Bost. 34. As to attraction, see ante, 13, 14; and 1 Arnott, El. Phy. 56, &c. (0) 1 Bost. 42 to 52; and see Quain's El. 2d edit. 23. (p) Id. 52 to 104. See also Jackson, Prin. Med. 18, 19, (7) Quain's El. 1st edit. 28 to 34; 2d edit. 21; the statements in the latter differ but little from the former. (r) Dr. Turner's El. Chemis. 154 to 174, where see full observations on nitrogen. (s) 2d edit. 21. (t) Quain, 1st edit. 28, 29; 2d edit. 21; see the Tables in Elliotson, Blum. 4th edit. 18, 19; 1 Bost. Phy.39, differ in some respect from that in Quain's El. 29. (u) See table El. Blum. 18, 19; Quain, 28, 29, 2d edit. 21; 1 Bost. Phy. 39; Dr. Turner's El. Chemis. 534. |