5, 
random (irrespective of their colour and appearance) and 
put through glucose and lactose broth. The results of these 
investigations are given in Table VI(a). Three tubes were 
inoculated for each step (3 Ic.c.; 3 ‘Ic.c., etc.) in the usual 
way. The + sign indicates that acid and gas were formed in 
all 3 tubes. If 2 out of the 3 gave acid and gas, asterisk is 
placed near the+; if r out of 3, a—sign with an asterisk, and 
if all 3 were negative a—sign is used to indicate this fact. 
The following points should be carefully observed in the 
fable VI(a) :— 7 
(t) That in practically every case a very much smaller 
quantity of the sample of water gives acid and gas in glucose 
than in lactose. If it were possible to make a sort of rough 
average out of these 77 samples, it would appear that in the 
lactose broth all dilutions up to 5 c.c. gave acid and gas, where- 
as in the glucose broth dilutions up to ‘I of a c.c. gave the re- 
action. If each sample is examined in turn, it will be found 
that out of these 77 only about 6 show that the number of 
organisms is approximately the same in both broths—(vide 15, 
20, 36, 49, 58, 75). It may also be noted that all, except 
one, of these samples are taken from rivers, or irrigation canals. 
It has been well known to water analysts for a very 
long time that what we may call ‘‘ the acid and gas line ”’ 
in lactose broth series is nearly always lower than in glucose 
broth. 
(2) A careful scrutiny of the results obtained from the 
separate colonies is also necessary. In the first place, out of 
770 colonies obtained from a lactose broth not a single one was 
glucose minus, that is to say, in this investigation all fecal 
lactose fermenters ferment glucose. On the other hand, the 
organisms grown in a glucose broth and plated on a lactose 
medium show very different results. The figures are found 
at the bottom of the Table VI(a), viz., about half of these 
organisms are glucose + lactose — . A very small percentage 
_ ferment neither glucose nor lactose ; no systematic study has 
been made of this small group up to the present. They are 
organisms which are obviously able to grow ina glucose broth 
without fermenting that sugar. 
