Some observations by Cyon on this subject deserve notice. Separating the heart of a frog, he connected it with a system of glass tubes and a manometer, and then passed through its cavities, first, serum saturated with carbonic acid gas, and afterward serum saturated with oxygen. The former caused sudden arrest in diastole, while the latter restored the movements of the heart Mr. Erichsen found, in experiments on asphyxiated animals, that ventricular contraction could be re-excited by oxygen when ordinary air had no effect. According to Hermann, oxygen is not indispensable for the cardiac contractions - they may occur without it, but irregularly; and if the gas be absent, or supplied in insufficient quantity, regular and synchronous contractions are impossible (Robin's Journal d' Anatomie et de Physio-logie, 1868-70).