VIII. Contributions to our knowledge of the connexion between chemical constitution, physiological action, and antagonism

The great object of Pharmacology is to obtain such a knowledge of the relation between the chemical constitution and physiological action of bodies as to be able to predict with certainty what the action of any substance will be. One of the most important steps towards this object was made by Crum-Brown and Fraser, who showed that the introduction of methyl into the molecule of strychnia or thebaia changed the tetanising action of those poisons on the spinal cord into a paralyzing one on the ends of the motor nerves. As the organic alkaloids are compound ammonias, it seemed probable that a similar change in the chemical constitution of ammonia itself might produce a corresponding change in physiological action. This was tested by Crum-Brown and Fraser, who found that trimethyl-ammonium iodide possessed a paralyzing action similar to that of methyl strychnia or methyl thebaia, while ammonia itself has been shown by Funke and Deahna to have a tetanising action very much like that of strychnia. A number of other ammonium compounds have been shown to have a similar paralyzing action; but there is no complete investigation of the whole series, nor has the relation of the acid with which the base is combined been determined.