1. Among a series of strains of haemolytic streptococci
from thirty -five cases of scarlatina in the first week
of illness, fourteen were found to correspond with one
or other of Griffith's serological types, I, II, III
2. Of these fourteen strains, twelve were selected for
further examination and found to yield a true heat - labile exotoxin completely inactivated by heating for
30 min. at 100 °C.
3. The concentration of exotoxin in 0.5 per cent
glucose broth cultures was at a maximum after 96 hourst
incubation, and thereafter on further incubation progressively diminished.
4. No qualitative difference could be detected among
the exotoxins from the different strains, the test
criterion being the dermal reaction in Dick-positive
5. Cultures of organisms of the same or different sero-
:logical type isolated from the same source and there - :after similarly treated yielded approximately equi:valent amounts of exotoxin.
6. Broth culture filtrates also contained an acid-insoluble toxic fraction, the concentration of which
increased with the age of culture and which appeared to
be identical with a similar acid -insoluble fraction
derived from an alkaline extract of washed bacterial
7. This acid -insoluble fraction was extremely heat - resistant, 3 hours' boiling at 100 °C being required
for inactivation. In this respect the acid -insoluble
fraction corresponded to the bacterial endotoxins.
8. The acid -insoluble fractions from cultures of the
same serological type produced equivalent skin reactions
in susceptible persons.
9. The acid -insoluble fractions from cultures of
different serological types differed qualitatively as
determined by skin reactions.
10. The reaction to crude filtrate was found to be the
sum of the reactions to the exotoxin fraction and to
the acid -insoluble fraction present in the filtrate.