An introduction to physiology . nt excitation. A similar condition can beproduced as follows : — Smoke a drum. Connect a dry cell through anopen key and an electro-magnetic signal with themetre posts of the rheochord (Fig. 41). Connectthe zero post and the slider of the rheochord withthe pole-changer (with cross-wires), and the latterwith two non-polarizable electrodes placed in themoist chamber. Make a nerve-muscle prepara-tion, and secure the femur in the femur clampof the moist chamber. Attach the muscle to themuscle lever. Bring the writing points of themuscle lever and the electro-magneti
An introduction to physiology . nt excitation. A similar condition can beproduced as follows : — Smoke a drum. Connect a dry cell through anopen key and an electro-magnetic signal with themetre posts of the rheochord (Fig. 41). Connectthe zero post and the slider of the rheochord withthe pole-changer (with cross-wires), and the latterwith two non-polarizable electrodes placed in themoist chamber. Make a nerve-muscle prepara-tion, and secure the femur in the femur clampof the moist chamber. Attach the muscle to themuscle lever. Bring the writing points of themuscle lever and the electro-magnetic signal 150 GENERAL PROPERTIES OF LIVING TISSUES against the smoked surface in the same verticalline. Let the nerve rest on the non-polarizableelectrodes. In the remaining two posts in themoist chamber fasten stimulating the latter to the inductorium, arrangedfor tetanizing currents, short-circuiting key the stimulating electrodes against the nervebetween the non-polarizable electrodes and the. Fig. 41. muscle. Let the secondary coil be at such a dis-tance that the tetanizing current will be justbelow the threshold value. Turn the pole-changerso that the anode shall be next the tetanizingelectrodes. Make and break the galvanic current,recording the contraction on a slowly movingdrum. Now open the short-circuiting key, andafter half a minute, and while the sub-minimaltetanizing current is still passing through the STIMULATION OF MUSCLE AND NERVE 151 nerve, make and break the galvanic currentagain. A moderately strong galvanic current will nowproduce an opening tetanus (anodal stimulationof a region the irritability of which has beenraised by the sub-minimal tetanizing current).Other effects are a lengthening of the latentperiod, and an increased dependence on theduration of the galvanic current (see page 138). Eeverse the pole-changer, so that the tetanizingelectrodes fall in the cathodal region. Eepeatthe experiment, comparing the results of c
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