would cause the formation in living matter of a great number of syntheses bj the building of anhydrides with the formation of water. The chief difference between living and lifeless protoplasm was about the difference between an anhydride and an acid. When death ensued, oxidation no longer took place, but the saponification continued until complete.
Although this hypothesis is necessarily difficult of proof, many facts indicate its possible truth. That protoplasm is the seat of reduction and oxidation no one will probably deny, and that by a process of alternate reduction and oxidation many of the transformations of substances by the organism may be repeated outside the cell is also undoubted. Thus Drechsel, by a rapidly alternating electric current, has succeeded in producing urea from albumin. It is also well recognized that many of the best-known syntheses effected by the organism are formed by a dehydration. This is true of the formation of fat, of the ethereal sulphates, of hippuric acid, of the camphor-glycuronic acid, and of the chondroit-sulphuric acid of cartilage. In this manner, too, as Hoppe-Seyler discovered, fatty acids of many carbon atoms may be synthesized from comparatively simple compounds. It seems not improbable that Hoppe-Seyler thus obtained a glimpse of that promised land toward which the physiological chemist has been patiently working for the past forty years, where the mysteries of protoplasm shall be made clear. Whatever may be the exact details of the process of respiration, certainly Hoppe-Seyler's discovery that reducing substances in the presence of air may induce powerful oxidations is one of the most brilliant and suggestive made in biochemistry.
Impressed by the similarity of living and fermentative processes, Hoppe-Seyler devoted much time to the chemistry of the latter. He made the first classification of fermentations, distinguishing those in which a simple hydration or saponification takes place, as in the digestive fermentations, from those characterized by the transference of an oxygen atom from a hydrogen to a carbon atom, with the liberation of hydrogen. To a certain extent he made clear the chemical processes of fermentation, and his researches serve as a solid and suggestive basis for further work. Hoppe-Seyler was throughout a strenuous upholder of the Liebig view of the essential identity of fermentations, whether induced by chemical bodies or living germs. His position has been justified by the recent brilliant discovery that the alcoholic fermentation of sugar by yeast, long believed to be dependent on the life of the yeast cell, is due to a substance which may be isolated from the living yeast. Hoppe-Seyler contributed also to our knowledge of the fermentation
