38 THOMPSON YATES LABORATORIES REPORT 
4. Water in the Maim and Service Reservoirs after filtration. — The three principal 
liquefactive groups mentioned above again make their appearance ; the B. fluorescens being in 
excess over the other two. 
5. IVater in the Dead Ends. — There are ahnost pure cultures of various groups of bacteria ; 
thus, in one case, the B. violaceus largely predominated ; in another case, a very beautiful iridescent 
bacillus ; in a third, a white liquefying organism giving rise to a pearl-like appearance in the 
gelatine. 
6. Water in the Wells. — Our investigations so far show chiefly slow-growing, non- 
liquefactive types. 
7. The bacteria present in the Sand of the filter beds. — In addition to the slow-growing 
bacteria previously mentioned, the B. rarnosus and B. violaceus were constantly found. 
In addition to the bacteria proper we have isolated a very characteristic group of higher 
forms, allied to the streptothrix and saccharomyces, and other forms of fungi, which produce 
various pigments, such as dark brown, pink, and white, and which emit a very characteristic and 
pungent odour, recalling the smell of damp cellars. In addition to photographing the plates, all 
the new colonies were isolated and inoculated on the various media, and their action studied 
on glucose gelatine, in broth, and in milk. 
We have thus formed a living herbarium, which at present numbers 115 specimens, 
although some of these may be found to be duplicates showing slight variations. We consider 
that the grouping adopted by Professor Marshall Ward to be far more satisfactory than trying 
to identify the bacteria with the innumerable forms described in various text-books. 
In the following classification we have adopted the group numbers of Professor Marshall 
Ward, having been readily able to identify these, and we have added some extra groups to 
include types not described in his list. 
Group 2. — Bacilli producing a violet pigment. — Seven members of this group were studied in detail. 
They all produce a blue pigment, varying in intensity from a light blue amethyst to a deep bluish-blacic, 
which is developed only after several days' incubation. After prolonged subculture in the laboratory they 
tend to lose their power of pigment production, and to become white. The optimum temperature is about 
20° C. No growth takes place at 37° C. 
On gelatine their liquefactive action varies, and is, as a rule, limited and slow. In milk they grow 
readily, and produce the characteristic pigment ; the medium becomes slightly acid, and in some instances 
a pellicle forms on the surface. The casein is not precipitated. 
In glucose gelatine no gas is produced. In peptone salt solution the pigment is produced, and often 
a pellicle on the surface. No formation of indol was noted. 
Group 3. — Fluorescent liquefying bacilli. — Six members of this group were studied in detail. 
They are distinguished by their smell and rapid liquefactive action on gelatine, and the formation of a 
greenish fluorescent pigment on agar and gelatine. They grow readily at all temperatures between 20° 
and 38" C. The casein in milk is rapidly precipitated, and subsequently completely peptonized with 
a slightly acid reaction. In glucose gelatine no gas is produced. In peptone salt solution they grow 
readily ; no indol is produced. 
Group 4. — Fluorescent 7ion -liquefying bacilli. — Six members of this group were studied in detail. 
They show a marked resemblance in many details to the previous group, and may be merely an enfeebled 
form of that species, more especially as the power of liquefying gelatine is often regained on subculture, 
though entirely absent on isolation. 
