black), which accelerates certain chemical reactions by the condensation of the reacting substances on the surface of the platinum, and their consequent increase in concentration. This process of condensation on surfaces is called adsorption. Warburg supposes that the oxidizing enzymes, oxidizable substances and oxygen are condensed on "surfaces," thus causing the oxidation rate to increase, but what surfaces he means it is difficult to determine, in some places apparently referring to surfaces of granules or colloidal particles, in others to cell or nuclear surfaces.
The adsorption of easily adsorbed substances may retard or prevent entirely the adsorption of others less readily adsorbed. Warburg found that anesthetics reduced the respiration of a mass of cell granules, presumably by driving the enzymes or oxidizable substances from their surfaces. He further observed that animal charcoal in water oxidized oxalic acid to , whereas if anesthetics were added the oxidation was reduced.
Warburg and Meyerhof found that the respiration of sea-urchins' eggs was not entirely destroyed by grinding with sand, presumably because the cell granules were left intact. They explain it, however, as an auto-oxidation or spontaneous oxidation of lecithin in the presence of iron salts, the oxidation taking place in the test tube. Warburg found iron and lecithin in the sea-urchin eggs and observed that if the total lecithin that could be extracted from a mass of eggs were mixed with a dilute solution of iron chloride, the oxidation was as great as that of the mass of ground cells. From his data we conclude that the mass of ground unfertilized eggs undergoes the same oxidation as does the same mass of cells if it were fertilized before grinding. Warburg interprets this as indicating that the oxidation of unfertilized eggs is due to auto-oxidation of lecithin, and that the increase in oxidation on fertilization is due to increase in structure (surfaces). Since mechanical agitations, however, may cause the eggs to develop, it is possible that the grinding first stimulated each egg to as great respiration as that of a fertilized egg, but the crushing and subsequent mixing of substances reduced the oxidation. It is interesting to note that, whereas unfertilized as well as fertilized eggs absorb oxygen and give off , ground eggs or lecithin and iron mixtures do not give off , indicating oxidation is not complete.
Relation of Oxidation to Permeability
R. Lillie supposed the oxidation within the unfertilized eggs to be suppressed by an accumulation of some end product of oxidation that could not escape. It is possible that such a substance might act like an anesthetic and suppress oxidation by adsorption to the granules. Lillie supposed this substance to be carbonic acid, but this is hard to
