284 Prof. A. J. Ewart. Comparative Study of Oxidation by 



3. The " incidence " of a sound is hence determined by its timbre and 

 loudness. Experimentally produced changes in the timbre or loudness of a 

 sound lead to marked changes in its apparent incidence. 



4. Tactual sensibility appears to play no part in auditory localisation. 

 Localised tactual sensations evoked by auditory stimuli are generally the 

 outcome of interpretations by the subject, resulting from his natural 

 tendency to treat sounds as material objects, and to refer to them a 

 localisation based on solely auditory data. 



A Comparative Study of Oxidation by Catalysts of Organic and 



Inorganic Origin. 

 By Alfred J. Ewart, D.Sc, Ph.D., Professor of Botany and Plant Physiology 

 in the Melbourne University and Government Botanist of Victoria. 



(Communicated by Prof. J. Eeynolds Green, F.B.S. Eeceived January 14, — 



Bead February 19, — Eeceived in revised form July 25, 1914.) 



CONTENTS. * page 



The Browning of Apples and Potatoes 285 



The Influence of Poisons on Browning 286 



Inorganic Oxidases : 287 



The Nature of Oxidases 290 



Oxidase Sensitisers and Inhibitors 292 



Sensitisers and Antagonisers to Plant Oxidases 296 



The Relation between the Action of Metallic Oxidases and that of an Enzyme 298 



Apple Oxidase 299 



The Chromogen of the Apple 300 



The Chromogen of the Potato 302 



Potato Oxidase 303 



The Extraction of the Oxidase 303 



The Distribution of the Oxidase in the Cell 305 



Colour and Oxidase Action 306 



The Destruction of Oxidase by Heat 307 



The Resistance of Oxidase to Drying and Keeping 307 



Paraphenylenediamine Test for Oxidase 308 



Ursol Tartrate Test for Lignin 309 



The Action of Paraphenylenediamine on the Oxidases of Apple Sap and Potato 310 



The Potassium Iodide and Starch Test for Oxidase in Living Tissues 311 



The Influence of Anaesthetics on Oxidase Action 312 



The Oxidases of the Lemon and Orange 314 



The Oxidase of the Carrot 315 



The Oxidase of Red Beetroot 315 



The Oxidase of the Parsnip 316 



Summary 317 



The present paper is the outcome of the work carried out on the influence 

 of poisoning on apples and potatoes, and its progress has necessitated a 



