STREPTOCOCCUS PYOGENES, 489 
established. Having, then, in remembrance the above 
facts, let us consider the results already obtained in the 
experimental immunization and treatment of animals 
and men suffering from or in danger of infection with 
streptococci. One method is now chiefly used for the 
immunization and attempt to produce curative sub- 
stances in animals. The living, virulent streptococcus 
itself is injected in gradually increasing doses. Mar- 
morek' was the first to attempt to produce a curative 
serum on a large scale. 
Influence of Serum from Animals Immunized Against 
Streptococcus Infection upon Streptococcus Infections 
in Other Animals. 
The results reported since Marmorek’s commu- 
nication in 1895 upon the immunizing effects of anti- 
streptococcic serum in animals have been very vari- 
able. 
Reliable positive results are, however, more impor- 
tant than negative ones, since they indicate under 
proper conditions what can be accomplished. This is 
certainly true if at the same time we can find good 
reasons for the failures reported. 
For the data in the following table I am indebted to 
Anna W. Williams, assistant bacteriologist in the Health 
Department Laboratories. For the use of the same I 
wish to express my appreciation. 
In this present table are given the results following 
the injection of small amounts of a serum which repre- 
sents in immunizing value what about one-third of the 
horses are able to produce. In the following experi- 
1 Annales de ]’Institut Pasteur, July, 1895, 
