Ward . — A Violet Bacillus from the Thames . 65 
marked alkalinity. The grey colour is due to the spreading 
of the purple through the milk. In a month nearly all is 
peptonized, and the liquid purple and very strongly alkaline. 
The colouring pigment cannot be detected in the Bacilli 
themselves under the microscope, but seems to be in the mem- 
brane — the swollen cell-walls forming the zoogloea-matrix 
— or even external to this. It is hardly, if at all, soluble 
in water, as is shown by the fact that on filtering water in 
which large quantities of the purple flecks &c. have been 
crushed, the liquid comes off quite or nearly clear ; but it is 
readily dissolved out by absolute alcohol. This alcoholic 
solution is, moreover, extremely stable, and I have kept 
a tube half full of it for more than six months unaltered in 
the dark at ordinary (spring and summer) temperatures. The 
beautiful blue-violet colour has a slight reddish cast in it, 
reminding one exactly of a solution of gentian-violet. 
The alcoholic solution shows one broad absorption-band, 
extending from the red to the green-blue ; but even a layer 
half-an-inch thick lets some of all the rays through. 
Acetic acid slowly renders the alcoholic solution paler. 
NaHO turns it bluish-green, the violet colour returning, but 
paler, with slight excess of HC1. 1 On evaporating the alco- 
holic solution to dryness over a water-bath, the purple sedi- 
ment dissolves up again in alcohol apparently unaltered.. 
Stable as it thus is, however, the solution exposed to the 
bright sunlight of an August day is completely bleached in 
from one to two hours. 
Old milk-cultures yielded Bacilli, the gelatine-colonies from 
which grew well, but were quite colourless, and very like those 
of B. Coli communis . It required several passages through 
broth and gelatine to get the colour up again. 
I have made numerous experiments with this Schizomycete 
to determine its relations to light, and find it one of the most 
sensitive as yet tried. It is quite easy to obtain sun-prints 
with agar-plates over which a stencil- letter is placed, with 
1 Practically the same reactions were observed by Mace with the violet pigment 
from his B. violaceus {Traite pratique de Bacteriologies 1892, p. 541). 
F 
