In papers which the authors have already communicated to this Society, they have shown that there exists a very marked difference between the action of bases containing nitrogen as a triad and those in which that element is pentad. This result was obtained from an examination of the physiological action of substances having an unknown and complex constitution. It appeared to be necessary to institute a series of experiments with bodies having a simpler and fully known constitution. For this purpose, the salts of ammonia, tri-methylamine, and tetra-methyl-ammonium were selected. A comparison of the structural formulae of the hydrochlorates of these bases shows that tri-methylamine stands in the same relation to the salts of tetramethyl-ammonium as strychnia to the salts of methyl-strychnium.