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 and IV.
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 hours' 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 persons.
5. Cultures of organisms of the same or different serological type isolated
from the same source and thereafter similarly treated yielded approximately
equivalent 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 bodies.
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