Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 THE CONTRACTILE TISSUES 99 a constant current can be sent through the electrodes and the whole length of the muscle. It is found, on making the current, that the lever attached to the kathode—that is, to the electrode by which the current leaves the muscle—rises before the other lever. On the other hand, on breaking the current, the lever at the anode rises iirst, showing that the anodic half of the muscle contracts before the kathodic half. h. The irritability of a muscle, its power of res
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 THE CONTRACTILE TISSUES 99 a constant current can be sent through the electrodes and the whole length of the muscle. It is found, on making the current, that the lever attached to the kathode—that is, to the electrode by which the current leaves the muscle—rises before the other lever. On the other hand, on breaking the current, the lever at the anode rises iirst, showing that the anodic half of the muscle contracts before the kathodic half. h. The irritability of a muscle, its power of responding to a stimulus by contracting, is intimately dependent on the life of the muscle. If the muscle be injured or killed at any spot, its irritability at this spot will be therefore diminished S)r destroyed. Hence, if we stimulate a muscle at the injured spot, no contraction will ensue. This fact may be used to Fig. 35. kathode j^ anode(injured) contraction at make anode rn kathode (injured) no contraction at make. b Diagram to show the effect of local injury on the excitability of a muscle, b, battery ; wj, muscle. The arrows indicate the direction of the current. demonstrate the production of excitation at kathode on make, and at anode on break of a constant current. A muscle with parallel fibres, such as the sartorius, is injured at one end, and a constant current passed, first from the injured to the uninjured end, and then in the reverse direction. It is found in the former case, when the anode is on the injured part (which is therefore less excitable), that break of the current is ineffective, and in the latter, when the kathode is on the injured surface, that the make stimulus is ineffective, showing that the part excited corresponds to the kathode at make and to the anode at break. Induced currents.—In using these the muscle or nerve is stimulated by the current of momentary duration produced in the secondary circuit of an induction coil by the make or
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