Hand-book of physiology / by William Senhouse Kirkes.

  • William Senhouse Kirkes
Date:
1856
Catalogue details

Licence: Public Domain Mark

Credit: Hand-book of physiology / by William Senhouse Kirkes. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

    54/780 (page 36)
    That whicli most characterises the contractility of animal tissues is, that the contraction may be excited by the applica- tion of a stimulus to the nerves that ramify in them; and, indeed, it is generally through the nerves that the stimulus which produces a contraction is conveyed. In the chapter on the Muscles it will be shewn, that the property of contractility is inherent in the tissues that contract, and is essentially inde- pendent of their nerves; so that contraction may take place without the co-operation of the nerves. Therefore, the whole property of irritability, including both the capacity of receiving a direct stimulus and the power of contracting in consequence thereof, may be ascribed to the muscles and other contractile tissues. But, in the ordinary conditions of life, the nerves may be said to be necessary to contractions, because, in these condi- tions, it is only through the medium of nerves that a stimulus is applied to the contractile tissues, and when the nerves are destroyed contractions do not naturally ensue. The modes in which stimuli are applied to, and their effects conveyed along, nerves to the contractile parts, will be described in the chapter on the Nervous System. One mode is essentially characteristic of animals; that, namely, wherein the contractile tissues are made to act by a ]\Iind, an Aniina; which, having knowledge of the existence of the body, consciousness of power and will to exercise it, acts on the nervous system,* and through it on the contractile tissues: thus voluntary motion is produced. 3. The power of conducting or transmitting stimuli or im- pressions which, in the foregoing paragraphs, has been ascribed to the nerves, constitutes another peculiar vital property. It belongs to the nervous system alone, and may be said to con- * It does so, at least, in all animals in which a nervous system can be demonstrated. In those in which none has been yet seen, it must be doubtful whether the mind can directly influence the contractile tis- sues, or whether some nervous material exists which we cannot discover, but through which the mind of the animal can act.