406 
Journal of Agricultural Research 
Vol. VIII, No. ii 
plate, and are gray, raised, and glistening. Under a power of 90 diameters 
they are found to be finely granular, more dense at the center, where a 
distinct nucleus is seen. At the periphery the colonies fade out to a very 
delicate stippled appearance, the margin entire and clear-cut without 
the pronounced outgrowths as in B. vulgatus , although they may show 
long finger-like radiating lobes; they are also unlike B. vulgatus in lacking 
the characteristic convolutions and mottlings. (PL 93, A). Deep colo¬ 
nies in the gross are gray and pinpoint-like. Under a power of 90 diam¬ 
eters the colonies are dense, quite irregular in form, and occasionally 
show slight mosslike branching. 
Gelatin colonies. —Colonies are at first barely visible. Under power 
these colonies are of all shapes, from circular to the most bizarre types 
imaginable, often resembling cockleburs with rather unusually long pro¬ 
jecting spines. Surface colonies are circular in outline, and liquefy, with 
the formation of a gray membrane which floats on the surface of the 
liquefied area. 
Bouillon. —The growth forms a heavy turbidity with a luxuriant 
growth around the wall of the tube at the surface which often does not 
until later close over at the surface of the liquid to form a complete cup¬ 
like membrane of luxuriant growth usually much resembling ground glass. 
The membrane usually turns yellow later. The turbidity increases and 
the medium remains often heavily turbid for days; later the turbidity 
may clear from the sinking of the organism and this, together with the 
sinking of the ground-glasslike membrane, which may be re-formed several 
times after sinking, produces a large amount of viscid sediment which 
may be made to arise from the bottom in the form of a long twisted spiral 
on agitation. A luxuriant ring growth is usually left around the wall of 
the tube at the surface. The above characteristics of bouillon growth ap¬ 
ply also to the various sugars—namely, glucose, lactose, saccharose, levu- 
lose, maltose, and the alcohol mannite. As regards the reaction in bouil¬ 
lon and the various sugars and mannite, it may be said that there is no 
sharp definite reaction, especially for mannite and plain bouillon. Usu¬ 
ally an acid reaction may be found at the fifth and tenth days in glucose, 
levulose, maltose, and lactose, when carefully titrated with N/20 sodium- 
hydroxid solution. Plain bouillon, mannite, and saccharose are less 
likely to show a perceptible change in reaction. So variable are these 
reactions that it would not be feasible to submit a type series. 
Gas production. —No gas is produced in fermentation tubes of glucose 
or in deep tubes of glucose agar. 
Serum. —There is usually some liquefaction, the resulting liquid being 
light to dark amber in color. 
Potato. —The growth varies in the same strain at different times and in 
the different strains. Usually, however, the growth presents a charac¬ 
teristic reticulated or netlike appearance. Often the growth above is 
smooth, glistening, raised, and butter-like. The color of the growth is 
