MICRO-ORGANISMS FOUND IN WATER 
39 
Group 5. — Colourless non-liquefying bacilli. — Twenty organisms were isolated and studied in detail 
^vhich could be referred to this heading. With one exception all showed variations from the typical 
cultural characteristics and reactions of the colon bacillus. For instance, many of them were incapable of 
precipitating casein in milk, though acidifying the medium ; only about half the number were able to 
produce gas in glucose gelatine, but one formed indol in peptone salt solution. They all grew readily on 
gelatine, without liquefj ing it, and on potato formed a well-marked yellowish growth. 
Group 6. — Common Proteus type. — Six forms were isolated and studied. One of the most marked 
features of this group, besides the ' wandering islets,' is the putrid smell produced by growth in milk and 
broth. Gelatine when liquefied by their action also acquires a sour odour. We have observed no 
variability in the liquefying power. Milk, as a rule, is acidified, and the casein precipitated and 
peptonized. The formation of gas in glucose gelatine is not constant. 
Group 7. — The yellow Proteus type. — Six forms were isolated and observed. They were closely 
allied to the last group, and onl}- differ in that they form a well-marked yellow pigment. 
Group 8. — J group which may be identical with Ward's Group 8. — Bacilli, forming irregular colonies 
of a beautiful iridescent appearance. Two members of this group were isolated for observation. They 
slowly liquefy gelatine. On agar and potato they form a yellow pigment. The casein in milk is pre- 
cipitated and peptonized with a faintly acid reaction. No gas is formed in shake cultures. No action on 
broth. They resemble in many particulars the preceding and the following group. 
Group 9. — Golden-yellow liquefying bacilli. — Seven organisms were isolated and studied in detail ; 
they differ in rapidity of liquefaction, but all form a golden-yellow pigment, and closely resemble Group 7 
— the yellow Proteus type — in their action on milk and glucose gelatine. 
Group 10. — Golden-yellow non-liquefying bacilli. — Five members of this group were isolated for 
observation. They are slow-growing forms, and are probabl)-, as Marshall Ward suggests, weakened 
varieties of the previous group, as their liqucfactive action is frequently regained on subculture, while their 
behaviour in milk is not constant. 
From our observations on Groups 6 to 10 inclusive, we are in agreement with Professor Marshall 
Ward's conclusions, namely, that these are merely varieties of one or two species, and that it is impossible 
to draw any hard-and-fast distinctions between the several groups. 
Group 13. — Bacilli producing a crimson pigment. — Two forms of this type were isolated and studied 
in detail. Cultures have a crimson-red metallic sheen with a marked trimethylamine smell. Gelatine is 
rapidly liquefied. No loss of liquefying power was observed. The casein in milk is precipitated and 
peptonized with an acid reaction, whilst later the tube contents acquire a crimson hue. In glucose gelatine 
gas is produced in forty-eight hours, whilst broth acquires a marked crimson tint. 
Group 15. — Bacilli conforming to the type of B. subtilis. — Thirteen organisms were isolated and kept 
under observation. From their study we have come to the conclusion that it is impossible to distinguish 
between the ' hay bacillus ' and the ' potato bacillus ' ; they are probably varieties of the same species. 
Under this heading we have included also well-known types, such as B. ramosus and B. megaterium, which 
from their behaviour on subculture conform closely to this type. 
The liquefactive action on gelatine is fairly constant, though some members tend to lose it on 
prolonged cultivation. The formation of a pellicle on the liquefied gelatine and in peptone salt solution 
is a distinguishing feature. 
The wrinkled growth on potato is common to all the members of this group, and cannot be relied 
upon to differentiate them. 
In milk the casein is rapidly precipitated and peptonized with the formation of varying degrees of 
acidity. The formation of gas in glucose gelatine is rarely observed. 
Group 16. — Sarcina forming a yellow pigment. — Two varieties were isolated and kept under 
observation. Members of this group produce a yellow pigment of varying intensity, which tends to 
decrease on prolonged subculture. The liquefactive action on gelatine varies considerably, as does their 
peptonizing action on milk. The true sarcina form of this group is not always maintained. 
Group 19. — Non-chromogenic micrococci. —Eleven organisms were isolated and studied in detail. 
Both liquefying and non-liquefying forms were met with, but this property is not constant, and in fact 
was found to be interchangeable. The microscopical appearances show wide differences, some members 
