Reflex Movements of the Frog under the Influence of Strychnia

Abstract

(From the Leipzig Physiological Laboratory.)As long as animals in a normal condition were used for experiments upon reflex movement, it seemed probable that these movements were limited by fixed anatomical associations of reflex centres into groups which connected certain nerves of motion with certain nerves of sensation'. Such an arrangement of cells and fibres in the central nervous system would explain the co-ordinated series of movements made to remove an irritation from a certain spot, as is seen on the application of a weak acid to the skin of the brainless frog. To explain the spread of the movements to new sets of muscles on increasing the irritation or the sensitiveness, one would need only to extend the hypothesis, and suppose these groups constituting the reflex apparatus to be connected in such a way that two or more could be brought into action at once without losing their several attributes.This theory fails, however, to explain the appearance and extent of the reflex convulsions in an animal poisoned with strychnia. When a certain amount of this alkaloid has been absorbed, any stimulus, wherever applied, causes, as is well known, a spasm in all the muscles of the body, as if all the motor nerves were connected in the circuit of an induction coil. If then, during strychnia poisoning, every motor nerve in the body is capable of being called into activity by the stimulation of any sensory nerve, all these nerves must be freely connected in the spinal cord; for the strychnia certainly cannot bring about a change in the arrangement of fibres.The small dose and short time required to produce strychnization lead to the supposition that a change takes place in the structure of