saccharifies starch, it is possible to tell
whether maltose or levulose and fructose are formed; if the former, only
those plates containing _P. phosphorescens_ will become luminous; if the
latter, only those containing _P. Pflugeri_. The more recent researches of
Molisch have shown that the luminosity of ordinary butcher's meat under
appropriate conditions is quite a common occurrence. Thus of samples of
meat bought in Prague and kept in a cool room for about two days,
luminosity was present in 52% of the samples in the case of beef, 50% for
veal, and 39% for liver. If the meat was treated previously with a 3% salt
solution, 89% of the samples of beef and 65% of the samples of horseflesh
were found to exhibit this phenomenon. The cause of this luminosity is
_Micrococcus phosphorens_, an immotile round, or almost round organism.
This organism is quite distinct from that causing the luminosity of marine
fish.

[Sidenote: Oxidizing bacteria.]

It has long been known that the production of vinegar depends on the
oxidization of the alcohol in wine or beer to acetic acid, the chemical
process being probably carried out in two stages, viz. the oxidation of the
alcohol leading to the formation of aldehyde and water, and the further
oxidation of the aldehyde to acetic acid. The process may even go farther,
and the acetic acid be oxidized to CO_2 and OH_2; the art of the
vinegar-maker is directed to preventing the accomplishment of the last
stage. These oxidations are brought about by the vital activity of several
bacteria, of which four--_Bacterium aceti_, _B. pasteurianum_, _B.
kutzingianum_, and _B. xylinum_--have been thoroughly studied by Hansen and
A. Brown. It is these bacteria which form the zoogloea of the "mother of
vinegar," though this film may contain other organisms as well. The idea
that this film of bacteria oxidizes the alcohol beneath by merely
condensing atmospheric oxygen in its interstices, after the manner of
spongy platinum, has long been given up; but the explanation of the action
as an incomplete combustion, depending on the peculiar respiration of these
organisms--much as in the case of nitrifying and sulphur bacteria--is not
clear, though the discovery that the acetic bacteria will not only oxidize
alcohol to acetic acid, but further oxidize the latter to CO_2 and OH_2
supports the view that the alcohol is absorbed by the organism and employed
as its respirable substance. Promise of more light on these