Elements of human physiology / by Henry Power.

  • Henry Power
Date:
1885
Catalogue details

Licence: Public Domain Mark

Credit: Elements of human physiology / by Henry Power. Source: Wellcome Collection.

    58/536 page 36
    CHAPTER III. MOVEMENT OP THE BLOOD. The movement of the blood is requisite that new material and oxygen may be brought to all parts of the system, and that waste material may be carried away. It is effected by the heart, which is a muscular organ divided into four cavities, between which valves are so arranged that the blood can pass in one di- rection only. There are two auricles and two ven- iricles. The right auricle and ventricle receive venous blood, and transmit it to the lungs, where it parts with carbonic acid gas and water, and takes up O, and then returns to the left auricle and ventricle. This is termed the lesser or pulmonic circulation. The left auricle and ventricle receive the arterialised or oxygenated blood, and transmit it to the system^ at large, from whence it is returned to the right auricle and ventricle. This is termed the greater or systemic circulation. The heart, therefore, although to outward appearance a single organ, is in reality double, the two halves being united for economy of space, and beating simultaneously. Action of tlie lieart.—The heart beats about 70 times in a minute, and the phenomena that may be observed are the following: In the first place con- traction and relaxation succeed each other in regular order. The period of contraction is termed the systole of the heart, the period of relaxation diastole. The two auricles contract simultaneously, then the two ventricles contract simultaneously, and then there is a pause. The systole and diastole together constitute one entire revolution of the heart's action. If the heart be
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