Valve (biology)

“ These valves are the tricuspid between the right auricle and right ventricle, the pulmonary semilunar valves between the right ventricle and the pulmonary artery, the mitral valve between the left auricle and the left ventricle, the aortic semilunar valves between the left ventricle and the aorta, and the valves which are scattered among the veins of the body. Of these by{76} far the most important are the valves in the heart: they do the chief work; those in the veins do little more than help. ”

“ Both the intake and outflow valves are composed of stout but thin sheets of membrane, so that very little pressure is required to operate them. The weight of the blood that is accumulated in the auricles during the beat of the ventricle is more than sufficient to force the valve open and allow the blood to flow on through into the ventricle. In a heart that is beating seventy-two times a minute, there cannot be much time occupied either in filling or emptying. ”

“ The cavities for the males are not formed, as in S. ornatum, by the thickening of the internal surface of the valve round a defined space, but by the scutum being externally convex and internally concave down the middle, hollows being thus produced both for the lodgment of the males and for the attachment of the adductor muscle. These hollows are separated from each other by a slight transverse ridge. I do not know at which point of the margin of the valve, the orifice of the male is situated, but I presume close under the apex. ”

“ It is seldom, if ever, attached to other bodies. Shell more finely lamellated than that of the oyster, free or slightly adherent, sub-equilateral, very inequivalve; the lower valve very concave, with a summit more or less recurved like a hook; the upper valve much smaller, and formed like a lid; hinge without teeth; ligament inserted in an oblong arched cavity; one single muscular impression on each valve. ”

“ The arterial openings, both on the right and on the left side, are provided with three-flapped semilunar-shaped valves, to prevent the regurgitation of blood when the ventricles contract. The veins emptying into the auricles are not capable of closure, but the posterior vena cava has an imperfect valve at its aperture.
The inner surface of the heart is lined by a serous membrane, the endocardium, which is smooth and firmly adherent to the muscular structure of the heart. This membrane is continuous with the lining membrane of the blood vessels, and it enters into the formation of the valves. ”

“ Brachial valve moderately to deeply concave, usually following rather closely the inside curvature of the pedicle valve, leaving scarcely a sixteenth of an inch as the probable thickness of the animal. ”

“ The hydrostatic valve consists of a flexible diaphragm, one side of which is in contact with the water outside, so that since the pressure increases with increasing depth, it is bent inwards more or less as the depth varies. ”

“ Of course the heart will not work well if its valves are not tight any more than will an ordinary pump, so that persons suffering from this trouble cannot have as good a circulation as those whose valves have nothing the matter with them. It is true that in most cases of imperfect valve action there is a compensation in the form of an increase in the size and strength of the heart muscle, so that the circulation is maintained in spite of poor valve action by harder work on the part of the heart. ”

“ When the chambers have attained their greatest state of expansion, the sides of the lower valve are forced upwards by the increased flow of the blood from the section below the valve, the lateral openings are closed, and the main current of the blood is projected through the two valves, as shewn in fig. ”

“ DICTYONEIS MARGINATA VAR. TYPICA CLEVE
Valve panduriform, with cuneate lobes; axial area narrow, linear, scarcely, or not at all, widened in the middle; terminal fissures in contrary directions; outer stratum finely punctate, about 25 in 10 μ, in parallel striæ; inner stratum coarsely reticulated. Four and one-fourth times longer than broad; marginal cells, 5 in 10 μ, smaller or obsolescent in the middle of the valve; cells of the valve in irregular transverse rows, 10-12 in 10 μ. ”

“ There are also valves at the roots of the arteries that permit the [Pg 208] blood to go from the heart into the arteries, but not to return. There are no valves at the roots of the veins that enter the auricles, nothing to obstruct the flowing of the blood from them into the auricles. Thus the roots of the veins arise from the auricles, and the roots of the arteries from the ventricles. Do you understand this description, because it is the foundation of all that follows—understand what a valve is?"
"Yes, sir; the clapper in our pump-box is a valve ”

“ SPONDYLUS. Auct. (A shell-fish, Ancients.) Fam. Pectenides, Lam. Sub-ostracea, Bl.—Descr. Inequivalve, sub-equilateral, irregularly foliaceous and spinose, auriculated, denticulated at the margins, attached by the lower and deeper valve; hinge rectilinear, with two prominent teeth in each valve, locking into corresponding cavities in the opposite valve; umbones separated by a broad, elongated, triangular disc in the lower valve; ligament contained in a groove, dividing the triangular area in the centre; muscular impressions one in each valve, sub-central, sub-orbicular. ”

“ An irregular, round impression will be found at each end of the valve, near the hinge-margin. These show where the muscles are attached to move and close the valves, and hold them firmly together. The muscles run directly across from one valve to the other; and, to open a live mussel, it is necessary to pass a sharp blade between the valves, and cut through the muscles, before the valves will open. These muscles are called the adductor muscles and the scars or impressions on the valves are called the adductor muscular impressions. ”

“ Shell solid, adhering, sub-regular, more or less spined, sub-auriculated, inequivalve; the right or inferior valve fixed, much more excavated than the other, and having behind, at the summit, a triangular face, which enlarges and elongates with age; hinge longitudinal, provided in each valve with two strong teeth entering into corresponding cavities; ligament short, almost medial, partly exterior; one sub-dorsal, muscular impression. ”

“ The valve of the right ventricle is composed of three flaps, and is therefore often spoken of as the tricuspid valve; it is in the same way membranous, and has chordae tendineae and musculi papillares connected with it. The disposition of the musculi papillares and their number differ in different mammals, but no exhaustive study has as yet been made of the arrangements in different groups; the amount of individual variation even is not known, though it is certainly considerable in some cases, for instance in the heart of the Rabbit. ”

“ The dorsal valve is uppermost.
In Lingula (Fig. 322) the muscular system is more complicated; in addition to the anterior (= anterior laterals) and posterior (= centrals) pairs of occlusors, there is a single divaricator (= umbonal) , whose contractions in conjunction with those of certain muscles in the body wall press forward the fluid in the body cavity, and thus force the valves of the shell apart; and there are three pairs of adjustor muscles. ”

“ The oxygen flows from the tank through a reducing valve, which cuts down the pressure, and into a controlling valve whence it flows by a rubber tube to the face cap which fits tightly over the patient's nose and mouth. ”

“ It is evident that the hardest task is demanded from the spiral part of the valve, for it is that part which is first brought to bear upon the wood. This part also has a more solid structure and the denticles are much finer; it is moved by a muscle of considerable size; the power of this muscle is, moreover, sensibly increased by the fact of its being implanted upon the two middle parts of the valves, each of which can be considered as a long arm of a lever whose extremity passes over a space at least four times as large as the portion of the valve which, strictly speaking, does the work. ”

“ The cell membrane is composed of two usually equal parts, each of which consists of a valve and a girdle or zone formed of cellulose modified by silica deposited in an insoluble state from a very dilute aqueous solution. The valves are more siliceous and robust than the girdle. Both are in most species easily separable, or at least the bands of the girdle which may be more or less closely fastened to the valves have a motion over each other permitting the cell to enlarge at pleasure. ”

“ Frustules stipitate, free or parasitic. Valves cuneate, elliptical or suborbicular, dissimilar, bent along the transverse or the longitudinal axes, the lower valve with a true raphe and central and terminal nodules, the upper valve with a pseudoraphe or median line.
Rhoicosphenia.—Stipitate; valves with transverse puncta, bent along the transverse axis, cuneate, with diaphragms at the ends.
Anorthoneis.—Free; puncta radiate; valves bent slightly along the transverse axis, suborbicular.
Cocconeis.—Parasitic; valves elliptical, usually bent along the longitudinal axis ”

“ Cephalic region occupying about one-fourth the area of the carpace, indicated by a slight change in the convexity of the valves and by several low, obscure elevations. The valves are each ornamented with two strong, longitudinal ridges extending nearly their entire length. The ridge nearer the dorsal line commences near the apex of the valve, following adjacent and parallel to the dorsal line to the base of the Cephalic area, and then diverging, extends almost to the posterior end of the valve, at about one-third the width of the valve from the hinge. ”

“ ACHNANTHES SUBSESSILIS KUETZ.
Valves linear-elliptical, rounded at the ends; upper valve with excentric pseudoraphe; striæ moniliform, puncta smaller than in A. brevipes.
Along the coast, in estuaries.
Pl. 16, Figs. 4, 5, 6.
The three species described above are named from the length of the stipe, but this varies considerably and is not of special significance.
ACHNANTHES INFLATA (KUETZ.) GRUN.
Valves more or less inflated in the middle, usually with the stauros of the lower valve asymmetrical and wider than in A. subsessilis, with which it agrees in size and markings. ”

“ Equivalve, inequilateral, transverse, rounded anteriorly, subrostrated posteriorly. Hinge with a central spoon-shaped cavity in each valve, containing the cartilage; a very small anterior cardinal tooth in each valve; two lateral teeth in one valve, none in the other: muscular impressions two in each valve, distant; palleal impression with a very large posterior sinus.—Obs. The species known at present are found in sand, in the fissures of rocks in Tropical climates. ”

“ The evolution of the spiral valve was probably due to the necessity of increasing the absorptive area of an almost straight unconvoluted intestine, a result which in other animals is often obtained by an increase in the length and concurrent convolution of the intestine itself. Any attempt to correlate the variations in the degree of perfection or imperfection of the valve considered as an absorptive mechanism with any special variations in the nature or quality of the food is, however, a very difficult problem, and a satisfactory explanation has yet to be found. ”

“ It consists of a hand of many pairs of fringed fingers, protected by a shell of five pieces, and a long flexible cartilaginous stalk, by the lower extremity of which it adheres to the timber.
The shelly valves are all crossed by strongly marked lines running over their surfaces in a direction parallel with each other, and with the outer margins of each valve. These, like the corresponding foliations in the tube of the Serpula, indicate the successive stages of growth; the outlines of every valve having stood at each of these growth [Pg 218] lines in succession. ”

“ Valve arcuate, with ends subcapitate; costæ radiate, 4 in 10 μ, alternating with double rows of puncta. Median nodule central, the raphe curved toward the ventral edge which it closely follows.
Parasitic on algæ. Very common in fresh water, especially in ponds. In the figure the valve is asymmetrical with respect to the transverse axis, an unusual condition.
Pl. 31, Fig. 14.
EPITHEMIA ARGUS KUETZ.
Valve with dorsal margin convex, and ventral margin nearly straight; ends rounded, constricted; costæ robust, alternating with more than two rows of puncta ”

“ The external surface of the valves is frequently ornamented with more or less prominent radiating ribs; and fine concentric growth-lines are commonly shown, and may be developed into coarse ridges or wrinkles, particularly in old individuals. The members of the family Productidae are usually furnished with tubular spines, which are sometimes of great length, and served to anchor the free shells in the mud, or were twisted round Crinoid stems and similar objects.
In the ventral valve of many genera there is a median sinus, with a corresponding fold in the dorsal valve, and rarely vice versâ ”

“ Frustule cylindrical, less in length than the diameter, in zone view undulated. Valve divided into six or more sectors alternately raised and depressed, areolate and punctate, varying in the alternate divisions. The areolation is confined to the outer layer of the valve while the punctation is usually on an inner valve often found detached. Processes on the border, three or more. Umbilicus circular or angular, hyaline. ”

“ The adjustors are four in number, a ventral pair running from the ventral valve to be inserted into the stalk, and a corresponding dorsal pair from the dorsal valve. The simultaneous contraction of either pair would tend to raise the valve, whilst the alternate contraction of the muscles of each side would tend to rotate the shell upon the peduncle. The muscles of Waldheimia flavescens are shown in Fig. ”