Cuticle

“ If the cuticle has been removed, there will be much suffering, because the nerves are unduly stimulated by the air. The cuticle is the sheath or covering of the vessels and nerves of the skin, and when it is removed, a substitute should be applied. ”

“ The cuticle is constantly undergoing renewal. This layer serves to cover and protect the nervous tissue of the true skin beneath. We may here observe that the cuticle contains the pigment for coloring the skin. In dark races, as the negro, the cuticle is very thick and filled with black pigment. The radiation of animal heat is dependent upon the thickness and color of this cuticle. Thus, in the dark races, the pigment cells are most numerous, and in proportion as the skin is dark or fair do we find these cells in greater or lesser abundance. ”

“ Mr. Beddard, in his invaluable 'Monograph of Oligochæta,' unfortunately leaves the subject almost untouched. He says (p. 13) : "The cuticle seems undoubtedly to be a formation of the packing cells of the epidermis; the pores upon its surface are the outlets of the gland-cells, and their existence appears to be simply due to the fact that the gland-cells do not secrete a cuticle like the other cells, their secretory activity being taken up in the formation of the granules with which they are laden; hence at the points where they abut upon the cuticle there are gaps—the pores in question." ”

“ The cuticle, epidermis, or scarf-skin, as it is indifferently termed, is formed of cells or scales, much flattened and horny in the upper layers, rounder and plumper below. The true skin, or “cutis,” is fibrous in structure, and lies immediately beneath, the two together constituting the skin, properly so called. Beneath lies a layer of tissue filled with fatty globules, and containing the glands by which the perspiration is secreted. ”

“ The body is covered externally by a chitinous cuticle which is a product of the subjacent epidermic layer in which no cell limits can be detected though nuclei are scattered through it. The cuticle is frequently prolonged into spines and papillae, which are especially developed at the anterior end of the body. ”

“ The extension of the cuticle is astonishing, if we consider that it is formed, as Grew well observes, on the tenderest embryo, and only extended during the growth of the plant, and that it appears not to have any connexion with the vascular or living part of the vegetable body. But though so accommodating in those parts where it is wanted, on the old trunks of most trees it cracks in every direction, and in many is entirely obliterated, the old dead layers of their bark performing all the requisite offices of a cuticle. ”

“ Whenever the cuticle is exposed to moderate and repeated friction, it becomes thicker and tougher, as may be seen in the cuticle of the lady’s finger that plies the needle and in the hard or callous appearance of the hands of farmers masons, and other mechanics. ”

“ The epidermis, placed immediately within the cuticle, is composed of a single row of cells, which vary, however, a good deal in size in different regions of the body. The cells excrete the cuticle, and, as shewn in fig. 32, they stand in a very remarkable relation to the secondary papillæ of the cuticle just described. Each epidermis cell is in fact placed within one of these secondary papillæ, so that the cuticle of each secondary papilla is the product of a single epidermis cell. ”

“ The epidermis consists of a single layer of cells which have a very thick continuous cuticle about one-half of the diameter of the whole cell. The cuticle differs in chemical composition from the rest of the cell walls, being impervious to water, and resisting rotting longer than do the cellulose walls. As it is continuous over the whole of the fruit, the skin can be readily separated from the other tissues. ”

“ In some species fine hairs appear, either on the entire body or only in the region of the neck, on the external surface. In the cuticle there can be recognized, besides the pores, which no doubt are concerned with nutrition, spaces in which lie the ends of sensory cells. Close under the cuticle lies the external layer of the parenchyma (basal membrane) , and below this the circular and longitudinal muscles forming the dermo-muscular coat. The matrix cells of the cuticle occur as in the Trematodes, only on the inner side of the peripheral muscles in the external zone of the parenchyma ”

“ This constitutes the disease called, “ac ́ne punc-ta ́ta.”
632. The PERSPIRATORY APPARATUS consists of minute cylindrical tubes, which pass inward through the cuticle, and terminate in the deeper meshes of the cutis vera. In their course, each little tube forms a beautiful spiral coil; and, on arriving at its destination, coils upon itself in such a way as to constitute an oval-shaped, or globular ball, called the perspiratory gland.
633. The opening of the perspiratory tube on the surface of the cuticle, namely, “the pores,” is also deserving of attention. ”

“ An epithelium of one layer is also found on the body of young stages, but it disappears during growth, and only occasionally do its nuclei persist until adult life. In its place we then find the cuticle, which, moreover, extends into all the body openings more or less deeply.
It is thus a debatable point whether the “investing layer” of flukes is a cuticle—that is, consists of modified epithelial cells—or whether it is a basement membrane, i.e., compressed and modified connective tissue cells; in this latter case the true epidermis and cuticle have been cast off. ”

“ What I should have said is, that a cuticle containing a dark pigment is less permeable by heat and light, because it is thicker and more opaque. For some reason, which I do not undertake to explain, the coloring matter of the skin, when abundant, is darker than when scanty. Hence, a cuticle containing a dark pigment is less transparent. And because abundance and consequent blackness of the pigment imply thickness of the cuticle, a dark cuticle does not transmit heat so readily as a light one. ”

“ In the cockroach the free surface of the cuticle is divided into polygonal, raised spaces or areas which correspond each to a chitinous cell of the hypodermis. (Miall and Denny.)
Numerous pore-canals pass through the cuticle of all the external parts of the body. The larger canals nearly always form the way for the passage of secretions from dermal cells, or connect with the cavities of hairs or setæ; when very fine and not connected with hairs or scales, they are either empty or filled with air, and may possibly serve for respiration. ”

“ By increasing the heat or prolonging its action the color becomes more distinct, till at the point of greatest intensity the cuticle becomes detached from its subjacent cutis by the gradual exudation and accumulation of a fluid which thus forms a true vesicle. ”

“ Neither can it be otherwise; for the Cuticle, from its transparency, must necessarily transmit the colour of the substance beneath it, in the same manner, though not in the same degree, as the cornea transmits the colour of the iris of the eye. This transparency is a matter of ocular demonstration in white people. It is conspicuous in every blush; for no one can imagine, that the cuticle becomes red, as often as this happens: nor is it less discoverable in the veins, which are so easy to be discerned ”

“ In portions of the cuticle of the medicinal squill (Scilla maritima) large cells are found full of needle-shaped crystals. These cells, however, do not lie in the same plane as the smaller cells of the cuticle. In the cuticle of an onion every cell is occupied either by an octahedral or a prismatic crystal of calcium oxalate. ”

“ When the cuticle is coated with impurities, blended with the secretion from the oil-glands, the sensibility of the skin is lessened.
863. The sensibility of the cutaneous nerves is modified by being habituated to impressions. If, for example, an individual should immerse his feet in moderately warm water, at first it might induce a smarting sensation; in a short time, the nerves would not only become habituated to the warm water, but its warmth night be considerably increased. The same results follow, if an individual is exposed to a cold element. ”

“ Du Hamel supposed this pulp to form the cuticle; but this is improbable, as his experiments show, when that membrane is removed, that the Cellular Integument exfoliates, at least in trees, or is thrown off in consequence of the injury it has sustained, and a new cuticle, covering a new layer of the same succulent matter, is formed under the old one. Annual stems or branches have not the same power, any more than leaves. ”

“ The whole body is covered by a thin cuticle secreted by the epidermis, which, as in the other groups, breaks down and forms a syncytium called the sub-cuticle. The minute fibrils which penetrate this layer are much more definitely arranged than in Nematodes; the largest of them run from without inwards, others run concentrically round the body. Large oval or spherical nuclei are scattered in the sub-cuticle, which is further honeycombed by a number of lacunae or spaces which are described below. ”

“ The cuticle is the portion of the covering of the body which may best be noticed when a blister has been raised in the skin. The blister is an accumulation of fluid between the cuticle and the true skin. ”

“ A slight degree of heat is productive only of redness of the surface, with a sharp hot pain, and these symptoms may subside with or without vesication. However, effusion of serum under the cuticle often takes place almost immediately after the contact of the heated body—the cuticle may be destroyed by the intensity of the injury—or the true skin may die, either partially or throughout its whole thickness, and the subjacent parts be at the same time injured to a greater or less depth. ”

“ Ecdysis.—The embryonic ectoderm of an insect consists of a layer of cells forming a continuous structure, the orifices in it—mouth, spiracles, anus and terminal portions of the genital ducts—being invaginations of the outer wall. This cellular layer is called the hypodermis; it is protected externally by a cuticle, a layer of matter it itself excretes, or in the excretion of which it plays, at any rate, an important part. The cuticle is a dead substance, and is composed in large part of chitin. The cuticle contrasts strongly in its nature with the hypodermis it protects. ”

“ Every part of a living plant is covered with a skin or membrane called the cuticle, which same denomination has been given by anatomists to the scarf skin that covers the animal body, protecting it from the injuries of the air, and allowing of due absorption and perspiration through its pores. ”

“ Nature has provided the body with a garment that is soft, pliable, close-fitting, and very thin, and yet sufficiently strong to enable us to come in contact with the objects that surround us, without inconvenience or suffering.
2. Microscopic examination? What is the cutis? The cuticle? Their union? How separated? What further is said of the cuticle?
2. The Structure of the Skin.—When examined with the aid of the microscope, the skin is found to be made up of two layers—the outer and the inner. The inner one is called the cutis, or true skin; the outer one is the epidermis, or scarf-skin. ”

“ Elliot and myself have closely examined the spot, and we have agreed that it is not an abrasion. Had the face been thus marked in the water, we should find the cuticle rubbed off, which is not the case. Contrarily, in the disease under consideration, the cuticle, though involved in the disease, and even missing in minute spots, is practically present. No, I am convinced that the mark on the body at the Morgue existed in life as the result of this lichen, though the alteration of color since death gives us a much changed appearance. ”

“ When the hair has arrived at the pore of the skin through which it is to pass, it is strongly enveloped by the pellicle of the root, which forms here a very small tube. The hair then pushes the cuticle before it, and makes of it an external sheath, which defends it at the time when it is still very soft. The rest of the covering of the hair, is a peculiar substance, and particularly transparent at the point. In a young hair this sheath is very soft, but in time becomes so hard and elastic, that it springs back with some noise when it is cut. ”

“ As already mentioned, the characteristic scales on the wings, legs and body of the Lepidoptera are cuticular structures. A complete series of transitional forms can be traced between the most elaborate flattened scales (fig. 7, B) with numerous longitudinal striae and a simple arthropod “hair.” Either a “hair” or a scale owes its origin to a special cell of the ectoderm (hypodermis) , a process from which grows through the general cuticle and forms around itself the substance of the cuticular appendage. ”

“ And the skin enveloping in a close case, keeps all compact, and hides from the eye whatever might be offensive: while, at the same time the cutis or true skin serves for a surface for the nerves and exhalent vessels to terminate, the cuticle or scarf skin defends them from injury, and moderates their excessive sensibility. ”