Auricle

“ Its thorax was immediately laid open, but no contractions were observed in any part of its heart, except in the right auricle, and even these were very slight. A plate of zinc was then placed in contact with the parvagum, and intercostal nerves, on one side of the trachea, and a half crown piece in contact with those of the other; both at the distance of about one third of an inch from the auricles. Every time the zinc and silver were brought into contact, complete contractions of the right auricle, and sometimes slight ones of the left were produced, but none in the ventricles. ”

“ The student who will take a little trouble in noticing the ears of the persons whom he meets from day to day will be greatly interested and surprised to see how much the auricle varies. It may be a thick and clumsy ear or a beautifully delicate one; long and narrow or short and broad, may have a neatly formed and distinct lobule, or one that is heavy, ungainly, and united to the cheek so as hardly to form a separate part of the auricle, may hug the head closely or flare outward so as to form almost two wings to the head. ”

“ The auricles are so small and so covered up by fat that from the outside you can hardly see them at all. What you chiefly see are two little fleshy corners, one of each auricle (Fig. 5, R.A. L.A.) , often called “the auricular appendages.” By far the greater part is taken up by the ventricles—and if you look you will see a band of fat slanting across the heart (Fig. 5, 3) . This marks the line of the fleshy division, or septum as it is called, between the two ventricles. You will notice that the point or apex of the heart belongs altogether to the left ventricle.{74}
Fig. ”

“ It is also to be noted that all animals which have a heart have also auricles, or something analogous to auricles; and, further, that whenever the heart has a double ventricle, there are always two auricles present, but not otherwise. If you turn to the production of the chick in ovo, however, you will find at first no more a vesicle or auricle, or pulsating drop of blood; it is only by and by, when the development has made some progress, that the heart is fashioned ”

“ In addition to this, there is a cross parting on each side, thus making four chambers, the two upper retaining the name of auricles, the two lower denominated ventricles.
"I will now explain to you the use of all this. The right auricle opens into the large trunk vein of the body, that, in connection with the others, brings back the blood from the extremities, after the arteries have distributed it. ”

“ P.V. pulmonary veins opening into the left auricle by four openings, as shown by the styles or pieces of whalebone placed in them: a, a style passed from auricle into ventricle through the auriculo-ventricular orifice; b, a style passed into the coronary vein, which, though it has no connection with the left auricle, is, from its position, necessarily cut across in thus laying open the auricle. ”

“ The right auricle when enormously enlarged, as in some cases of pneumonia, in emphysema, and in leukæmia, may form a large mass occupying a considerable space in the antero-lateral part of the thorax. The walls in dilatation with thinning are flabby and relaxed, and collapse at once when cut, but in dilatation with hypertrophy they are firm, especially those of the right ventricle. ”

“ Nauwerck Method. By this method the left auricle, left ventricle, right auricle and right ventricle are opened in succession. The heart is seized in the left hand, and without rotation is drawn upon the right edge of the ribs. Beginning in the upper left pulmonary vein or between the veins an incision is made through the wall of the auricle to the sulcus circularis, avoiding any injury to the coronary vessels. Beginning below the mitral ring an incision is carried along the left ventricular ridge to the apex. ”

“ The auricle of the human ear presents many irregularities of surface. If these irregularities are abolished by filling them up with a soft material such as wax or oil, leaving the entrance to the canal free, experiment shows that the intensity of sounds is weakened, and that there is more difficulty in judging of their direction. When waves of sound strike the auricle, they are partly reflected outwards, while the remainder, impinging at various angles, undergo a number of reflections so as to be directed into the auditory canal. ”

“ The left auricle is situated at the back of the base of the heart, behind and to the left of the right auricle. Running down behind it are the oesophagus and the thoracic aorta. When it is opened it is seen to have a much lighter colour than the other cavities, owing to the greater thickness of its endocardium obscuring the red muscle beneath. ”

“ I have several times opened the breast and pericardium of a man within two hours after his execution by hanging, and before the colour had totally left his face, and in presence of many witnesses, have demonstrated the right auricle of the heart and the lungs distended with blood: the auricle in particular of the size of a large man’s fist, and so full of blood that it looked as if it would burst. ”

“ The heart receives blood from the gills and mantle, and pumps it through arteries to the body. It consists of a median ventricle with muscular walls and a cavity traversed by muscular strands. On either side of the ventricle, in the primitive condition, is a thin-walled auricle, opening into the ventricle by a valved opening. Each auricle forms the terminal enlargement of the efferent vein of the ctenidium of its own side. In Nautilus two pairs of auricles are present, corresponding with the two pairs of ctenidia. ”

“ The ventricle, however, tends to dilate as well as enlarge in thickness of walls, and as soon as this dilatation has proceeded so far as to widen the orifice between the auricle and ventricle and render its valves insufficient, the auricle also begins to dilate and its walls often increase in thickness. ”

“ Those between the auricles and ventricles are considerably larger than those at the commencements of the great arteries. Those on the right side of the heart too are greater than those on the left. They vary with the form of the heart. Thus in dilatation of an auricle and ventricle on one side of the heart, the auriculo-ventricular opening becomes equally widened and the valves remaining disproportionately small the blood is allowed to rush back into the auricle during ventricular contraction. ”

“ In addition to these the beginning of the ventral aorta is often thickened and expanded to form a bulbus arteriosus, which is non-contractile, and, strictly speaking, should rather be described with the arteries than with the heart. In relation to human embryology the smooth sinus venosus and reticulated auricle are interesting. Between the auricle and ventricle is the auriculo-ventricular valve, which primarily consists of two cusps, comparable to the two endocardial cushions of the human embryo, though in some forms they may be subdivided. ”

“ In a short time longer the sensibility of the heart is greatly diminished, for the blood is seen to be accumulating in both the auricle and ventricle, but especially in the former, from both of which cavities it is now only partly expelled by the contraction of the heart. ”

“ The ventricles failing and coming to a stand, the motion still goes on in the auricles, and finally in the right auricle alone; and even when all motion has ceased, there the blood may still be seen affected with a kind of undulation and obscure palpitation or tremor, the last evidence of life. Every one, indeed, may perceive that the blood—this author of pulsation and life,—longest retains its heat ”

“ This soon shows four dilatations, which, from the tail towards the head end, are called the sinus venosus, the auricle, the ventricle and the truncus [2] arteriosus. As the tubular heart grows more rapidly than the pericardium which contains it, it becomes bent into the form of an S laid on its side (∾) , the ventral convexity being the ventricle and the dorsal the auricle. ”

“ When the auricles contract they are seen to become whiter, especially where they contain but little blood; but they are filled as magazines or reservoirs of the blood, which is tending spontaneously and, by its motion in the veins, under pressure towards the centre; the whiteness indicated is most conspicuous towards the extremities or edges of the auricles at the time of their contractions. ”

“ The auricular muscles consist of an outer coat common to both auricles, the fibers of which are transverse and of an inner coat, independent for each auricle, the fibers of which are longitudinal. Between the two coats, occur bundles of muscle the fibers of which run in various directions. The disposition of the muscle tissue of the ventricles is much more complicated. It is composed of several layers of fibers intricately interwoven.
The endocardium, covering the inner surface of the myocardium, forms a serous lining of all the chambers of the heart. ”