exists between the values of assimilated carbon and those of oxidized nitrogen.” This is illustrated by the results of various experiments as shown in Table I. [8] Winogradsky, S., “Die Nitrification,” _Handb. d. tech. Mykol._, 1904-06, iii., 132. [9] Winogradsky, _loc. cit._, p. 163 and ff. TABLE I --------------+---------+---------+---------+--------- | _No. 5_ | _No. 6_ | _No. 7_ | _No. 8_ +---------+---------+---------+--------- | _mg._ | _mg._ | _mg._ | _mg._ Oxidized N | 722.0 | 506.1 | 928.3 | 815.4 Assimilated C | 19.7 | 15.2 | 26.4 | 22.4 --------------+---------+---------+---------+--------- Ratio N:C | 36.6 | 33.3 | 35.2 | 36.4 --------------+---------+---------+---------+--------- It is obvious that 1 part of assimilated carbon corresponds to about 35.4 parts oxidized nitrogen or 96 parts of nitrous acid. These results of Winogradsky were confirmed in very careful experiments by E. Godlewski, Sr.[10] [10] Godlewski, E., _Anz. d. Akad. d. Wissensch. in Krakau_, 1892, 408; 1895, 178. The nitrites are further oxidized by another kind of micro-organisms into nitrates and they also can be raised without organic material. Winogradsky had already previously discovered that the hydrogen sulphide which is formed as a reduction product from CaSO₄ or in putrefaction by the activity of certain bacteria can be oxidized by certain groups of bacteria, the sulphur bacteria. Such bacteria, _e. g._, _Beggiatoa_, are also commonly found at the outlet of sulphur springs. They utilize the hydrogen sulphide which they oxidize to sulphur and afterwards to sulphates, according to the scheme: (1) 2H₂S + O₂ = 2H₂O + S₂ (2) S₂ + 3O₂ + 2H₂O = 2H₂SO₄ The sulphuric acid is at once neutralized by carbonates. Winogradsky assumes that the oxidation of H₂S by the sulphur bacteria is the source of energy which plays the same rôle as the oxidation of NH₃ plays in the nitrifying bacteria, or the oxidation of carbon compounds--sugar and others--in the case of the other lower and higher organisms. Winogradsky has made it very probable that sulphur bacteria do not need any organic compounds and that their nutrition may be accomplished with a purely mineral culture medium, like that of the nitrite bacteria. On the basis of this assumption they should also be able to form sugars from the CO₂ of the air.