In a paper on “The Pharmacological Action of Protocatechyl-tropeine,” communicated to the Society in 1909, I drew attention to the fact that this substance, when injected intravenously in certain doses produces transient paralysis of the respiration; and I mentioned further that Tappeiner had described a similar temporary cessation of the respiration after the intravenous injection of certain quaternary isoxazol and pyrazol compounds, and of tetra-methyl-ammonium chloride, and Pohl, after the intravenous injection of some quaternary papaverine derivatives. Tappeiner came to the conclusion that the effect was due to stimulation of the terminations of the fifth cranial nerve in the nose; that it was, in fact, of the nature of a Kratschmer-Hering reflex, since he was unable, in the case of methyl-phenylisoxazol-methochloride, to produce cessation of the respiration after anæsthetising the nasal mucous membrane with cocaine; and Iodlbauer, working in Tappeiner's laboratory, also found that anæsthetisation of the nasal mucous membrane prevented the cessation of the respiration produced by tetra-methyl-ammonium chloride. Pohl, on the other hand, was able to produce this temporary paralysis of the respiration after section of the ophthalmic branches of both fifth nerves, and consequently he concluded that the effect was due to an action on the respiratory centre. I came to the same conclusion, since the effect was still obtained with protocatechyl-tropeine after section of both fifth nerves in the base of the skull and after section of both phrenic nerves, and was not synchronous with the effect on the circulation or with the paresis of the nerve-endings in the muscles of the hind limbs. Further work with tetra-methyl-ammonium chloride, however—my stock of protocatechyl-tropeiue being exhausted,—showed that the effect was in large measure peripheral and due to a transient paresis of the nerve-endings in the respiratory muscles.