( 637 } 
polymyxa, B. nitroxus , B. sphaerosporus, B. luteus, besides in the 
anaerobes Granulobacter butylicum , Gr. saccharobutyricum and Gr. 
pectinovorum. 
The moulds, the various yeast species, even those which invert 
cane-sugar, besides all species of Streptothrix, and most of the non¬ 
spore producing bacteria, do not produce the emulsion either. 
An exception to the last rule makes the non-spore producing Azoto- 
bacter chroococcum, which on plates of 2 % of agar, 2 to 10 % cane- 
sugar, and 0,02 % K,HP0 4 , in water, gives a strong emulsion, 
which extends to a large distance round the colonies; later, in their 
vicinity, perhaps by the influence of a specific enzyme or an acid 
it vanishes, while near the colonies of the soil-bacilli the emulsion 
is permanent. With, the exception of B. chroococcum the other 
forms of Azotobacter do not produce the emulsion. From cul¬ 
tures of Azotobacter, prepared with garden soil and destined for 
the absorption of free nitrogen, a species related to B. radiobacter 
can be obtained, which produces no spores, but does also give a 
strong emulsion. 
Ane mulsion, from a physical view analogous'but quite different by 
the manner in which it takes rise, was described by me on another occa¬ 
sion 1 ). It appears when a 10 u /„ solution of gelatin in water is boiled with 
a 10% solution of soluble starch, or with a 2% agar-solution. Even 
by boiling the two watery solutions do not mix, which, of course, 
is also the case after solidifying. This reposes evidently on the fact 
that here two colloidal solutions are brought together, which cannot 
diffuse and whose emulsionated droplets constantly have a positive 
surface-tension with regard to each other. The same explanation 
must hold • good for the emulsion formed by the viscosaceharase 
with regard to the agar, and as I may add, to culture-liquids 
wherein Bacillus emulsionis produces the emulsion also. 
The emulsion is produced by an enzyme. 
If from the etriulsion field round a colony a small piece of agar 
is cut out, witjhout touching the colony, and placed on an other cane- 
sugar-agar-plate, the emulsion itself does not diffuse out of it, but 
into the plate, a substance goes over, which produces the emulsion 
again and with regard to the quantities used rather strongly. This 
points with certainty to the presence of .an enzyme as the cause of 
the emulsion, an enzyme which must have the property of moving 
through the agar by diffusion. This agrees perfectly well with the 
i) Centralbl. f. Bacteriologie 2* Abt, Bd. 2, p. 627, 1896. 
