104 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Bactericidal Influence of Hydrogen peroxide.* — Herr Dieudonne, 
after exposing uninoculated agar plates for ten minutes to direct sun- 
light, or for 3J-4 hours to diffused daylight, was enabled to demonstrate 
the presence of peroxide of hydrogen by means of iodide of potassium, 
starch, paste, and sulphate of iron (Schonlein’s reaction). With gelatin 
plates the reaction was manifested in five hours. By covering part of 
the capsule containing the agar with blackened paper and then exposing 
it to the sunlight, the presence of peroxide of hydrogen could be demon- 
strated in the illuminated portion only of the agar, while in the covered 
it was wanting. The effective rays in the formation of hydrogen per- 
oxide are the blue and violet, the red and yellow having no such 
influence. Even tap-water, when exposed to the sun for a couple of 
hours, showed a slight reaction on the addition of ether, bichromate 
of potash, and dilute sulphuric acid (blue colour). The reaction was 
most manifest in the upper layers, the middle showing it less clearly, 
and the lowermost scarcely at all, even after prolonged exposure. Upon 
the formation of hydrogen peroxide depends in great measure the bac- 
tericidal action of light. Illumination-experiments, made with cultures 
of Bacterium coli with exclusion of oxygen, showed that these organisms 
were not killed off with exposure to light in the absence of oxygen under 
four hours, but when oxygen was present one and a half hours sufficed. 
The author is inclined to explain the self-purification of streams, which 
according to Buchner essentially depends on light, by the formation of 
hydrogen peroxide. 
Production of Ammonia in the Soil by Microbes. f — The conver- 
sion of nitrogenous organic bodies into nitrates by the lower organisms 
is divisible into three phases : — (1) The formation of ammonia from the 
organic matter ; (2) the oxidation of the ammonia to nitrite ; (3) the 
further oxidation of the nitrite to nitrate. M. E. Marchal has recently 
devoted some attention to the first phase of this mineralisation process, 
and gives experimental proof that no ammonia is formed from organic 
substances in the soil without the co-operation of microbes — bacteria, and 
mould fungi. Of the former fifteen species are enumerated, of the latter 
five, which were found to possess the power of converting albumen into 
ammonia. It is inferred from these experiments that the formation of 
ammonia from albuminous substances is not a specific function of certain 
organisms, like nitrite and nitrate formation, but is common to a large 
number of micro-organisms. 
Whether the mould fungi or bacteria are more efficient as producers 
o* ammonia in the soil was determined by experiment in favour of the 
bacteria ; for in highly cultivated land, either on account of its alkaline 
leaction, which is favourable to bacteria, or because of the absence of 
large quantities of organic matter, mould fungi were decidedly re- 
pressed. If, however, the reaction were acid, though rich in organic 
substances, mould fungi flourished. To a description of the morpholo- 
gical and .cultural characters of B. mycoides Fliigge the author devotes 
much attention. 
* Arb. a. d. Kaiserl, Gesund., ix. (1891) p. 537. SeeBot. Centralbl., lxiii. (1895) 
pp. 63-4. 
f Agricult. Science, viii. (1891) p. 574. See Centralbl. f. Bakteriol. u. Paru- 
sitenk., 2 te Abt., i. (1825) pp. 753-8. 
