io6 
Notes on Recent Literature. 
longer than the length of the cover-glasses used (see Fig. 15). 
The straight portion is now heated in the flame of a Bunsen 
burner, dipped into the wax and gently applied, so that the wax- 
covered wire lies along the edge of the coverslip, from which super¬ 
fluous glycerine should have been previously removed. The melted 
wax which adheres to the wire at once solidifies where it touches 
the glass and forms a neat and strongly adhesive joint. After 
each edge has been sealed and any superfluous wax scraped off 
with a knife, the slide is ready for use. The line of wax should 
adhere to the clean and dry portions of the glass at least along 
its inner and outer edges. If the specimens are to be kept for 
some time, a thin coating of gold-size may be painted over the wax. 
The method has several advantages. The slides may be sealed 
up very quickly and used at once. The wax never percolates under 
the coverslip, as Gold Size and Brunswick Black often do. The 
coverslip can be easily removed with a knife, if at any time it is 
desired to restain or remount the section. 
I am indebted to Professor Nathorst for the above particulars. 
H. H. T. 
NOTES ON RECENT LITERATURE. 
Iron-Bacteria. 
T HE existence of bacteria which have the power to live in absence 
of organic foods was established by Winogradsky’s well known 
classical researches on the nitrifying bacteria. These organisms 
proved not only to require no organic carbon in the nutrient medium 
on which they were cultivated, but to be injured by the presence of 
organic compounds even in very small concentrations. 
A few years before this discovery, Winogradsky had investigated 
a species of another group of bacteria, the iron-bacteria, and his 
observations suggest a similar conclusion with regard to this 
organism. Leptothrix ochracea is a filamentous bacterium enclosed 
in a gelatinous sheath. In presence of this bacterium ferrous 
carbonate is oxidised and a precipitate of ferric hydrate accumulates 
in the sheath. For this precipitation, as also for the life of the 
organism, free oxygen is essential. Under the conditions prevailing 
in Winogradsky’s cultures Leptothrix only grew when supplied with 
ferrous carbonate, and it was concluded that the oxidation of iron 
played an essential part in the metabolism of the bacterium. 
Winogradsky did not follow up this first preliminary investigation 
with more critical experiments. Meanwhile Molisch found that 
Leptothrix ochracea could store manganese in place of iron, and 
succeeded also in cultivating the same species in organic nutrient 
media in the entire absence of iron and manganese. In opposition 
to Winogradsky’s view he maintained that the oxidation and 
