Chemical Stimulation of the Nerve Cord of Lumbricus Terrestris

Nerve cells of different functions cannot be differentiated histologically by staining methods. In order to prove chemical differences it is necessary t o affect the function of a given type of neuron by the action of a chemical agent. Thus Baglioni 1 has demonstrated a chemical difference between sensory and motor cells in the frog and the squid, by showing that phenol is an excitant for the motor ganglia alone while strychnine stimulates the sensory ganglia only of these forms. Maxwell ~ has shown that the nerve cells of the mammalian cortex are sfimulatedby one class of substances which includes creatine and strychnine, but that such substances do not act on medullat.ed nerve fibers. Only certain salts, such as the calcium precipitants and barium compounds, act upon medullated fibers. On the other hand these salts do not stimulate the gray matter of the brain. Tetraethyl-ammonium chloride is an exception in that it acts upon structures of both types2 I t is possible that chemical differences exist between nervous systems of various forms. 4 For example, coelenterates give no spasm response to strychnine, but echinoderms do, provided the concentration of alkaloid is sufficiently high, while cephalopods a re as sensitive to strychnine as vertebrates are. On these grounds ParkeP has suggested that strychnine might be used as a test for the presence of synapses, since sensitivity to strychnine on the part of different