64 Ward . — A Violet Bacillus from the Thames. 
with grey or yellowish-brown, forms in from two to five days, 
and slowly spreads ; it varies considerably as to thickness, 
wet or dry appearance, and rate of growth (Fig. io). 
Generally, but not always, the violet colour begins to appear 
about the fourth day, and then invades the mass, and a tough, 
deep violet, corrugated and mamillated membrane is formed 
as on agar, but not so extensively. In some cases the cultures 
on potatoes fail altogether to produce the pigment, and I am 
unable to say why. Very often the violet colour does not 
extend to the edges, but remains towards the centre. 
In broth, at 20° C., turbidity is just perceptible on the 
second day, and this increases. Later on a thick membrane 
forms above, the liquid below being very turbid. The mem- 
brane is at first white, and may remain so for ten days or more. 
In strong cultures the violet hue appears sooner or later, and 
in twenty days there is a tough, much corrugated, violet 
membrane floating on the still turbid liquid, at the bottom 
of which a white deposit collects. The colour of the membrane 
deepens as the culture ages, and it clings so tightly to the 
walls of the tube that the liquid does not escape on upturning. 
Broth at 35 0 gives no growth in four or five days — the liquid 
is perfectly clear. 
Carrot at 2 5 0 C. Spreads as a white film in forty-eight hours, 
and in three days is a purple and white paste. In fifteen days 
much spread as a white, wet, pasty layer, but only small patches 
of purple here and there. 
Artichoke at 25° C. Much as on carrot, but perhaps more 
waxy. In fifteen days the white wet paste is smeared with 
blue-violet patches. 
Milk undergoes slight coagulation, and the separated casein 
is slowly peptonized, or peptonization may occur without 
evident precipitation. The reaction of the liquid is alkaline. 
After some time — it may be three or four weeks — the violet 
pellicle forms on the surface, deepening in colour from day to 
day. In some cases, at 25 0 C., traces of violet occur above 
in a week, and in the deposit in a fortnight, and still no 
change is evident in the milk, except a grey colouration and 
