Collagen

“ The presence of collagen fibrils varies between the adaxial and the abaxial connective tissue layers. au = auricle, bl = basal lamina, cc = central cavity, cf = collagen fibril, ci = cilium, ct = connective tissue, ec = exterior cavity, ep = epithelial cell, fa = fascicle, ic = interradial cavity, ip = interpyramidal muscle, lo = lobe, mf = muscle fiber, np = nerve process, nu = nucleus, ph = pharynx, po = postural muscle, pr = protractor muscle, pv = perivisceral coelom, py = pyramid, re = retractor muscle, to = tooth. ”

“ Pure glutin or gelatin is obtained by treating buckshorn, etc., with water containing hydrochloric acid, until the phosphate of lime which serves, so to say, as a frame for the glue-yielding substance, is dissolved, and the organic tissue called collagen or ossein, remains behind. ”

“ The procedure of alkali slow etching opens the possibility to observe the forms of collagen fibrils located within silica layers of spicules and their distribution. The results obtained by SEM observations of the desilicified spicular layers provide strong evidence that collagen fibrils’ orientation within M. chuni spicules possesses twisted plywood architecture (Figures 3 (c) and 3 (d) ) . The twisted plywood or helicoidal structure of collagen fibrils is well-described by Giraud-Guille [30] for bothin vivo and in vitro [31] systems. ”

“ The fleshings obtained by hand labour contain distinctly more hide substances than those obtained by machine work, and their commercial value to the gelatine manufacturer is of course proportionate to the collagen content. Some hides and skins are split in the pelt (Part I., Section IX.; Part II., Sections II., III. and IV.) , and the "flesh split," though sometimes made into leather, is also used in making gelatine, a high quality being obtained from such material. ”

“ Diagram 20.—A Connective-tissue Cell giving rise to Long Collagenous Fibres.
Bone is formed very much as if Nature were rectifying a mistake. When a rod of cartilage is unequal to its work it is eaten hollow, and fresh connective-tissue cells immigrate and fill up the cavity, eventually laying down a fine network of cells in its place, the meshes of which are filled with inorganic calcium salts, chiefly phosphate of lime. Nature then benefits by experience, and the last bones to be formed are not preceded by any makeshift cartilage, but built up straight away in ordinary connective tissue. ”

“ Proteins occur in nearly every part of all animals, and the "protoplasm" of the living cell is itself a protein. The keratins include the horny tissues of animals: the epidermis proper, the hair, horns, hoofs, nails, claws, the sebaceous and sudoriferous glands and ducts, and also the elastic fibres. The gelatins are obtained from the collagen of the skin fibres, the bones, tendons, ligaments, cartilages, etc. Fish bladders yield a strong gelatin. The albumins are obtained from the ova, blood, lymph, muscles and other internal organs of animals. ”

“ Experiments in the laboratory and in practice have shown that it is not the dissolving action on the skin substance in the narrow sense which is desired in bating the derm with dogs’ dung, but in order to prepare the hide for the manufacture of a soft and elastic leather, the albuminous intercellular substances and more particularly the layers of fat lying at the roots of the hair, in the corium and in many cases also on the epidermis, must be dissolved and thereby the fibrils of the skin loosened. ”

“ The mesodermic portion of the skin consists of loose, subcutaneous connective tissue containing some fat. The amount of adipose tissue in the subcutaneous layer is subject to great variation; there are a few places in which there is little or no fat. The upper portion of this layer contains a few elastic fibers, which interlace and run in all directions. Numerous round or oval cells are found in the upper region. The lower and middle portions of the corium are richly supplied with blood-vessels terminating into capillaries, which penetrate the portions bordering the epidermis. ”

“ Only these features are less marked in the first than the second, because in the last more wrinkles are formed than in the other, by the contraction of the same muscles.
The cellular texture is in greater or less quantity in the face in different people. Every one knows that some are always thin in this part, who are fat in the rest of the body. From the dissection of the bodies of such persons, I have found that it arises from the small quantity of cellular texture it contains in proportion to the other parts. ”

“ It is from this inner layer of the epidermis that the hair, the sweat-glands, and the fat-glands are developed.
The corium, or true skin, consists essentially of white, interlacing fibres of the kind known as connective tissue. These fibres are themselves made up of extremely fine smaller fibres, or fibrils, cemented together by a substance of a somewhat different nature from the fibres, the coriin. Towards the center of the skin, the texture of the interweaving [22] fibres is looser, becoming much more compact at the surface just beneath the inner layer of the epidermis. ”

“ We observe the structure of the skin—whether it be fine or coarse in its texture, whether it be hard and unyielding, or soft and elastic. We note the quantity of fat and of cellular tissue; and this enables us to form a judgment respecting the degree of embonpoint, and we have already abundantly proved that a man of a soft, lax habit, with an abundance of cellular and fatty tissues, differs in mental tendency and disposition from one of firm, tense fibre, in whom the bones, muscles, and articulations, are strong and prominent. ”

“ F, fat globules and connecting fibres.
We are continually Shedding our Skin. One way in which the skin keeps itself so wonderfully clean and fresh is by continually shedding from its surface showers of these fine, dry, scaly cells, which drop, or are rubbed off, as they dry. This is the reason why no mark, not even a stain or dye, upon the skin, will stay there long; for no matter how deeply it may have soaked into the layers of the pavement-cells, every cell touched by it will ultimately grow up to the surface, dry up, and fall off, carrying the stain with it. ”

“ This board is to put the skin over in order to hold it better while removing particles of fat and flesh which adheres to it while skinning, which can be done with a blunt-edged knife, by scraping the skin from the tail down toward the nose — the direction in which the hair roots grow — never scrape up the other way or you will injure the fiber of the skin, and care should be taken not to scrape too hard, for if the skin fiber is injured its value is decreased. ”

“ In the centre of each hair is the medulla or pith, though this is not always present; it is composed of nucleated cells containing pigment, fat and air spaces. Outside this is the fibrous layer or cortex, also containing pigment and air spaces, while most superficially is the cuticle made up of overlapping scales. The hair grows at its root from a hair follicle (see fig. 2) , which is a tubular inpushing of the epidermis into the true skin or, in the case of large hairs, deeper still into the superficial fascia. ”

“ The superficial layer, the epidermis or cuticle, is composed wholly of epithelial cells, of which the deepest layer is columnar and moulded upon the papillary layer of the derma, while the intermediate layers are more rounded and the surface ones flat. The deepest layer also contains the skin pigment, which causes the variation in shade between the Indian, the negro, and the white man. Below the epidermis, which is chiefly protective, is the tough, elastic, and flexible tissue of the derma or true skin, in which are vested most of the activities of the skin. ”

“ The pulp of the fruit under the skin begins to shrink and contract as the juices dry up, and, quite naturally, the skin which was once taut and smooth, now being much too large for the contents, puckers up and lays itself in tiny folds. It's the same way with the skin of the face. When the subcutaneous fat of the cheeks and brow—which, when we are young and plump and rosy, is abundant—begins to be absorbed and to gradually disappear, then the cuticle straightway starts in to shrivel and fall into minute lines. ”

“ While, in the body of a starving or sick individual, the fat disappears and the muscular tissue takes once more the form of blood, we find that the tendons and membranes retain their natural condition, and the limbs of the dead body their connections, which depend on the gelatinous tissues.
On the other hand, we see that the gelatine of bones devoured by a dog entirely disappears, while only the bone earth is found in his excrements. The same is true of man, when fed on food rich in gelatine, as, for example, strong soup. ”

“ Connective tissue yields gelatine on boiling, and is the part which tans when hides are manufactured into leather. It is very elastic, so that when you remove your finger after pressing upon the skin, no indentation is left. [Footnote: In dropsy, this elasticity is lost by distension, and there is a kind of "pitting," as it is called, produced by pressure.] It varies greatly in character,—from the mucous membrane, where it is soft and tender, to the ligaments and tendons which it largely composes, where it is strong and dense. ”

“ The third excretion from the skin, the epithelial or superficial scales of the epidermis, is small in weight, but it is solid, and of similar composition to gelatin. It should be understood that this increases largely with exercise. The practice of sponging and ‘rubbing down’ of athletes removes the excess ”

“ Put up in glycerine, or stain rather strongly with carmine, and mount in balsam. The same method of treatment may also be applied to other hard berries or seeds.
30. Fat.—Adipose tissue may be hardened in alcohol, cut in paraffine, and mounted in glycerine. If the tissue has been injected the sections may be mounted in balsam, and are then very beautiful objects, showing the capillary network encircling the fat cells.
31. Hair.—Longitudinal sections are readily made by splitting the hair with a sharp razor. It is more difficult to cut the hair transversely. ”

“ Fig. 1 shows a section of ox-hide, cut parallel with the hair, magnified about 50 diam.: a, epithelial layer or epidermis, consisting of horny layer above, and rete malpighi below; b, pars papillaris, and c, pars reticularis of corium, derma, or true skin; d, hairs; e, sebaceous or fat-glands; f, sudoriferous or sweat-glands; g, opening of ducts of sweat-glands; h, erectores pili muscles, for erecting the hair.
The fresh hide consists of 2 layers: an outer, the epidermis; and an inner, the true skin. ”

“ The skin also contains little sacs, or follicles, in which the hairs originate. In its deeper portions are found two kinds of glands; sebaceous glands for the secretion of sebaceous or fatty matter to lubricate the skin, and the perspiratory or sweat glands, the latter of which will receive a more definite description shortly.
The Cuticle, or Epidermis.—At the upper portion of the true skin, new cells are being constantly formed, which become old in a short time and are pressed outward by the formation beneath them of other new cells. ”

“ In this process, the skin imbibes a considerable quantity of lime, which has the effect of either removing from the hide or skin, a portion of the gelatinous substance, in the form of soluble gelatine, or, of altering the gelatinous fibre, so as to render it incapable of speedily and effectually combining with the tannin or tannic acid, and the pores of the skin are so impregnated with lime, as to prevent the tanning principle from operating freely, or reaching the heart of the skins. ”

“ Naturally, there is a deposition of fat in the cellular tissues, which gives the particular appearance which the French call embonpoint, which simply means that the nutrition which has hitherto gone to the development of the figure is now em­ployed in the accumulation of adipose matter beneath the cuticle. When, however, the overtaxed membrane gives way, the tissues relax, and the muscular fibres losing their tenacity, fail to maintain their normal position. ”

“ These tissues of mixed character form what is called connective tissue, which is found throughout the body.
Fat is deposited in little cells situated in the connective tissue.
Muscular tissue, which forms the great bulk of the body, is easily recognized by its ruddy color, and it constitutes what is known as “flesh.” It is fibrous, and if these fibers be examined under the microscope there will appear, in those under the influence of the will, transverse markings, while the muscles not under the will-power lack these markings. ”

“ As the irritation is continued the skin continues growing harder and thicker, until a large and ugly corn is produced. To understand its nature more fully, and why it assumes a sharp point, thus turning its protection into a torture, it will be necessary to explain something more of the nature of the skin itself.
There are two layers of membrane composing the skin—the cutis vera, dermis, or true skin, which is the inner portion; and the cuticle, epidermis, or scarf-skin, which is the outside layer. ”

“ The skin of the forehead is without hair, is well nourished, and has little adipose tissue underlying it, facts that make it especially useful for these operations. The skin surface he turns into the mouth cavity, while the outer or raw surface is covered with a pedunculated skin flap taken from the region of the intramaxillary region. ”