A textbook of human physiology / translated from [the] 6th German edition by W. Stirling.

  • Landois, Leonard
Date:
1888
Catalogue details

Licence: Public Domain Mark

Credit: A textbook of human physiology / translated from [the] 6th German edition by W. Stirling. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    blood is discharged into the aorta and pulmonary artery, '^^f^^^^^X^^^^'^ the opposite direction, i.e., downwards and slightly outwards. Landois ho ^e^er has shown that the nmss of blood is discharged into the vessels O-Ob o second after the beginning of the systole, while the cardiac impulse occurs with tiie nrst ''^^S? When the blood is discharged into the aorta and pulmonary artery, these vessels are slightly elongated, owing to the increased blood-pressure. As the heart is suspended from above by these vessels, the apex is pressed slightly downwards and forwards towards the intercostal space (?). As the cardiac impulse is observed in the empty hearts of dead animals, (4) and (5) are certainly of only second-rate importance. Filehne and Pentzoldt maintain that the apex during systole does not niovc to the left and downwards, as must I. II. Fig. 40. I. Schematic horizontal section through the heart, lungs, and thorax, to show the change of shape which the base of the lieart undergoes during contraction of the ventricle—F, G, transverse diameter of the ventricle during diastole ; c, position of the thoracic wall ; a, b, transverse diameter of the heart during systole, with c, position of the anterior thoracic wall during systole. II. Side-view of the heart—i, apex during diastole ; j;, during systole, be the case in (4) and (5), but that it moves iipward and to the right—a result corroborated by V. Ziemssen. [Barr attributes the cause of the impulse to the rigidity or hardening of the ven- tricle during systole, to the rotatory movement and lengthening downwards of the blood- column in the aorta and pulmonary artery, while towards the end of the systole the maximum of recoil takes place and also contributes to cause it.] It is to be remembered tliat as the apex is always applied to the chest-wall, separated from it merely by the thin margin of the lung, it only presses against the intercostal space during systole {Kiwisch). After the apex of the curve, c, has been reached at the end of the systole, the curve falls rapidly, as the ventricles quickly become relaxed. In the descending part of the curve, at d and e, are two elevations, which occur sirimltaneoudy iviili the second sound. These are caused by the sudden closure of the semi-lunar valves, whereby an impulse is propagated through the axis of the ventricle to its apex, and thus causes a vibration of the intercostal space ; d corresponds to the closure of the aortic valves, and e to the closure of the pulmonary valves. The closure of the valves in these two vessels is not simultaneous, but is separated by an interval of 0-05 to 0-09 sec. The aortic valves close sooner on account of the
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