A Study of the B. enJi Group. 
used for immunisation, while with another strain of the same type (No. 2) it 
was necessary to employ 0-025 c.c. of antiserum to obtain this degree of 
complement absorption, and on diminishing the amount of antiserum there 
was a rapid falling off in the amount of complement deviated (Table XX). 
With representatives of other typical B. coli varieties, the amounts of 
complement deviated by different quantities of antiserum were practically 
the same as those deviated with the No. 2 strain of type B4. Thus even 
by varying the amount of antiserum no demarcation could be demonstrated 
in the A sub-group between, for example, types 1 and 3 on the one hand 
and type 4 on the other. This was found to be true also in the case of 
antisera to types 1 and 3 of sub-group A (Tables XXI and XXII). 
Experiments were also carried out in which the amount of antiserum was 
maintained constant and the quantity of antigen varied; with the antiserum 
to strain 1 of type 1 no differentiation could be established between another 
type I strain and a strain of a different type (type 2) (Table XXIII). 
Ctkoup Eeactions. 
The group reaction was then studied to ascertain its significance as 
regards the biological relationships between different types and the 
classification or grouping of these organisms. 
G-roup action by complement deviating sera has been studied in other 
bacterial classes ; thus Sacqucpce found that the food-poisoning group could 
be classified into two sub-groups (Enteritis I and II). An immune serum 
to an organism of sub-group I reacted with other sub-group I types but not 
with organisms of sub-group II: similarly an antiserum to a sub-group IE 
type reacted only with other organisms of the same sub-group. 
On testing the antiserum to strain 1 type 4 {B. Grunthal) along with a 
large number of different coliform strains (typical and atypical) it was 
found that the group reaction was limited to a certain class. If these 
coliform bacilli are divided up as follows, as in the original classification given 
above (p. 323) : 
Coliform bacilli. 
Gas producing Those that do not produce gas from 
aerogenes") any of the sugars fermented 
types. anaerogenes") types. 
I Sub-group D. 
I 
. I . . I 
Non-inosite fermenters. Inosite fermenters. 
I Sub-group C. 
Indol forming, Non-indol forming. 
Suh-group A. Sub-group B. 
then sub-group A will comprise all the typical varieties, e.(j. B. MacConkey 
31 
