The human frame and the laws of health / by Dr. Rebmann and Dr. Seiler [tr. from the German by F.W. Keeble].

  • Rebmann, Edmund.
Date:
1900
Catalogue details

Licence: In copyright

Credit: The human frame and the laws of health / by Dr. Rebmann and Dr. Seiler [tr. from the German by F.W. Keeble]. Source: Wellcome Collection.

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    The movements executed by the human body are voluntary and involuntary. In the latter dass are included reßex movements. Voluntary movements depend for their performance on the action of the will. To this dass belong the usual movements of the limbs, though those involved in walking have been rendered reflex by continued practice. Involuntary movements, such as those of the heart, stomach, intestine, iris, etc., are elFected quite independently of the will. Speaking generally, the striated muscles are the means of voluntary movements, the unstriated of involuntary move- ments. But in the heart, the muscle, which differs in other respects from skeletal muscle, is striated, though its movements are involuntary. Again, the muscles concerned in respiration are only very slightly under the control of the will, and yet are of the ordinary striated kind. The reßex movements do not result from an impulse initiated in the brain, but from a Stimulus from without. This gives rise, generally through the medium of the sense-organs, to a nervous impulse. This impulse, reaching the spinal cord or the brain, sets up changes which result in other nervous impulses putting the muscles concerned in the movement in action. On hearing a loud report, we dose our eyes; on stumbling, we Stretch our arms forward ; when we are startled, we involuntarily draw back. These reflex movements are usually effected before the knowledge of them reaches the consciousness, and, indeed, may be carried out without the knowledge of them or their cause ever reaching the consciousness. There is yet another group of movements in which the will mayexert some little influence. For instance, we may strengthen, or accelerate, or for a short time stop, the respiratory movements, though the Operation of breathing usually takes place without any influence of the will. Very few movements are single, that is to say, executed by a single muscle. Most are composite, so that several muscles
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