. Electro-physiology. Electrophysiology. 118 ELECTRO-PHYSIOLOGY CHAP. is sooner or later a spontaneous excitation of the nerve-fibres, as shown first in twitches of the fibrils and then in tetanic con- traction of the entire muscle (desiccation- and salt-tetanus). If the excitability of such a nerve is tested from time to time with a current of uniform strength, it is found to increase, until, just before the commencement of desiccatory spasm, each closure, or opening, discharges powerful but irregular tetani. The closure- tetanus of " cooled " nerves, on the contrary, is usually qui
. Electro-physiology. Electrophysiology. 118 ELECTRO-PHYSIOLOGY CHAP. is sooner or later a spontaneous excitation of the nerve-fibres, as shown first in twitches of the fibrils and then in tetanic con- traction of the entire muscle (desiccation- and salt-tetanus). If the excitability of such a nerve is tested from time to time with a current of uniform strength, it is found to increase, until, just before the commencement of desiccatory spasm, each closure, or opening, discharges powerful but irregular tetani. The closure- tetanus of " cooled " nerves, on the contrary, is usually quiet and regular, the curve showing no marked divergence from the tetanus-curve of intermittent excitation. The conjecture that closing and opening tetani are due to abnormal activity in the nerve, is completely contradicted by the fact that the motor. FIG. 171.—Tetanus curve of gastrocnemius on closure of a battery current (closure tetauus). Preparation from a cooled frog. (Von Frey.) nerves of other animals invariably react by tetanus, under all cir- cumstances. This applies, according to Eckhardt's observations (5), especially to nerves of warm-blooded animals, when excited with descending currents of average strength, as well as to the non-medullated motor nerves of many invertebrates (claw nerve of crayfish, etc., Biedermaim). In both cases closure-tetanus is the rule and not the exception, and thus du Bois' "universal law " has as little application to indirect as to direct excitation of the muscle. We must rather hold that, although the visible effects of the transmitted excitation are fundamentally due to variations of density in the current flowing through the nerve, the excitatory process is locally initiated throughout its cnfir* •jtassage, and that other circumstances determine whether this continuous excitation is expressed at the peripheral organ (muscle) or no. The same applies to the state of activity at break of the. Please note that these images ar
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