189) 
Canal water is now flowed over the plate and the excess removed 
so that isolated colonies can develop; or on the surface of the plate 
streaks of various species of bacteria are made and the plate is 
then kept at 25° to 30° C. After a few days around most of the 
colonies or streaks the said reaction appears with great distinctness. 
Tartrates, citrates, succinates, glycolates, salts of volatile acids, and 
sugars do not give the reaction. 
The experiment may be modified in different ways, for example, 
by using instead of broth agar a culture medinm of the composition : 
100 tapwater, 1 calciummalate, 0,1 ammoniumsulfate, 0.02 potassium- 
fosfate, with some ferric citrate as an indicator, and furthermore 
„treated as above. The less favourable source of nitrogen is cause 
that on such a medium a smaller number of species of bacteria 
grow, but the reaction is as distinct, and the proportion of the active 
to the non-active germs on the ammoniacal medium even greater 
than on the broth-agar plate. 
The species that cause the conversion may be arranged in the 
following order according to their intensity of action. 
The most vigorous splitters are B. fluorescens, B. jl. liquefaciens, 
B. calco-aceticus and B. pyocyaneus. Then follow B. aerogenes, B. 
viscosus and B. levans, and some varieties of B. violaceus. 
A little less active are B. coli, B. proteus, B. prodigiosus, B. 
kieliensts, and the vinegar bacterium Acetobacter rancens. Quite 
inactive are B. termo, B. punctatus, B. devorans, B. ochraceus, 
and the luminous bacteria; nearly inactive are the vinegar bacteria 
Ac. melanogenum, and Ac. pasteurianum. 
Nor do the moulds and yeasts examined up to now produce 
pyruvic acid, although many of them readily oxidise the malates to 
carbonic acid and water. 
As some bacteria such as B. pyocyaneus, B. aerogenes, B. levans, 
B. viscosus and some moulds and yeasts are able also to oxidise 
the pyruvates themselves to carbonate and water, one might suppose 
that the species which appear not to produce pyruvic acid from 
malic acid, in fact do so, but only as a transition product, but what 
follows is in contradiction with this supposition. First, the pyruvates 
are less readily attacked than the malates, so that accumulation 
and not oxidation of the pyruvates would become probable. Secondly 
experiments prove that the ferric salt solution enters the microbie 
cells. As now the oxidation of the pyruvates like that of the malates 
undoubtedly takes place in the interior of these organisms, the 
presence of the pyruvie acid ought to cause a colouring of them, 
which is not observed. 
