Observations were made on rabbits and cats under dial anesthesia. Monopolar recording from cortex was used. Strychnine, 1%, on motor cerebral cortex is excitatory, as shown by increased firing of motor units; later the strychnine induces cortical spikes. Each spike is triphasic, consisting of an initial, small positive wave, a large, fast negative wave, and a final, slow positive wave; the first two waves are believed to be excitomotor; the final positive wave is regarded as a positive after-potential with relative quiescence of neurons; it is not excitatory for motor units. Microwaves at high frequency occur during first positive wave and ascent of negative wave; microwaves decay during descent of negative wave and are absent during final positive wave. Microwaves are caused by fast, repetitive firing of neurons; this neuronal firing causes excitation of motor units. Intracortical and extracortical conduction are believed to be repetitive. Acetylcholine (ACh), 1%, on eserinized cortex induces triphasic spikes, resembling those from strychnine; microwaves are likewise present. Strychnine, eserine, and ACh are believed to stimulate cortical synapses. Strychnine and ACh, though very different chemically, are believed to trigger the same fundamental cortical mechanism of conduction.
DETERMINATION OF THE LENGTH AND PENETRATION POINT OF THE MASSETERIC NERVE IN THE MASSETER MUSCLE
