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Updated: May 4, 2025
"In the lowest and simplest class of excited movements," says Mueller, "the nervous system would not appear to be concerned. They result from stimuli directly applied to the muscles, which immediately excite their contractility; and they are evidently of the same character with the motions of plants." Thus, the heart is excited to pulsation by the direct contact of the blood with the muscle.
The nucleus controls, though it may not entirely carry on, the constructive metabolism. It is equally clear that the cell substance is the seat of most of the destructive processes which constitute vital action. The cell substance is irritable, and is endowed with the power of contractility. Cell fragments without nucleii are sensitive enough, and can move around as readily as normal cells.
The chief part of this apparatus is formed, as in all the higher animals, by the active organs of movement, the muscles; in consequence of their contractility they have the power to draw up and shorten themselves. This effects the movement of the various parts of the body, and thus the whole body is conveyed from place to place.
It is not too much to say that one-half of a modern text-book of physiology consists of applied physics and chemistry; and that it is exactly in the exploration of the phenomena of sensibility and contractility that physics and chemistry have exerted the most potent influence.
The protoplasm of Algæ and Fungi becomes, under many circumstances, partially, or completely, freed from its woody case, and exhibits movements of its whole mass, or is propelled by the contractility of one, or more, hair-like prolongations of its body, which are called vibratile cilia.
Among the lower plants, it is the rule rather than the exception, that contractility should be still more openly manifested at some periods of their existence.
The pupils of his eyes broadened out to the circumference of his iris, and his limbs seemed to diminish as if endowed with the contractility peculiar to the mollusca and certain of the articulate; for Frycollin, the valet, was an egregious coward. He was a pure South Carolina Negro, with the head of a fool and the carcass of an imbecile.
Reduction of ocular tension by stimulation of osmosis, of lymphagog activity, of absorption of edema, and of capillary contractility, and by decreasing affinity of ocular colloids for water. The Myotics.
And this power of change of form is a lower grade of the contractility of our muscular cells. Prick it with a needle and it contracts. It recognizes its food even at a microscopic distance; it appears therefore to feel and perceive. Perhaps we might say that it has a mind and will of its own.
Irritability is that property of a substance which enables it to respond to a stimulus, or to act when acted upon. The property of contractility enables the muscles to produce motion. Irritability is a condition necessary to their control in the body. *Kinds of Muscular Tissue.*—Three kinds of muscular tissue are found in the body.
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