9 
eroups differ in the dejecta of men and cattle, and that it may 
be possible to use these figures as a guide in ascertaining which 
of these two sources gives rise to any specified pollution. Hf 
we can give definite answers to these questions, we shall be 
in a position to compare the flora of faeces with that of water 
and to draw conclusions accordingly. Since July 1908 the 
subject of the flora of feeces has been under continuous investi- 
gation. Very many analyses have been carried out. The 
subject of the comparison between MacConkey’s work and ours, 
and the use of his four classes will be first dealt with. The 
method adopted in these analyses is as follows :— 
An emulsion is made with a fair quantity of faeces in water 
(usually one gram. in 9 c.c.). This emulsion may be treated 
in two ways: (1) A drop is placed in the centre of a bile salt 
neutral red lactose agar plate. This is wiped over the surface 
of the plate. The same glass wiper is then applied to two 
similar plates. The isolated colonies obtained are picked 
off after 18 to 24 hours’ incubation at 37°C or 42 C and put 
through various tests. 
(2) A few drops of the mixture are placed in bile salt 
lactose broth, and incubated for 18 hours. <A loopful of the 
culture is then spread on the bile salt plates and the colonies 
treated in the same way. It may be stated that these 
methods give practically identical results. From a great deal 
of experience of both we find that the use of the broth culture 
does not alter the relation of organism in feces. This is a 
rather important finding. 
It should be remembered that it was suggested by 
MacConkey to divide all lactose fermenting organism into 4 
groups, according as they did or did not ferment saccharose 
and dulcit. 
Group (1) ferment neither saccharose nor dulcit ; 
Group (2) ferment dulcit but not saccharose ; 
Group (3) ferment dulcit and saccharose ; and 
Group (4) ferment saccharose but not dulcit. 
The figures are given below and the results obtained have 
been tabulated in Tables II (a) and (0). 
