316 THE STREPTOCOCCUS-PNEUMOCOCCUS GROUP 
are given. From 1 to 3 injections usually suffice. The objective to be 
attained is to make and keep the fluids of the body antitoxic. 
The serum seems to have comparatively little value in the treatment 
of the complications which are so common in scarlet fever, but it does 
have unquestioned effect in preventing the development of many of 
these complications, hence the value of early administration. 
This leads to mention of the fact that the Dick method of active 
immunization against the poisons of the scarlet fever streptococcus has 
little or no protective value against the streptococci themselves: in 
other words, a person may be rendered tolerant of the soluble poison, 
but might succumb to an actual invasion of the organism. The same 
may be said of the Dochez serum. It appears probable that the 
mechanism of scarlet fever involves lodgment and growth of the strep- 
tococcus in the mucus membrane of the mouth or upper respiratory 
tract, then formation and absorption of the poison, followed by the 
manifestations of scarlet fever— angina, fever, rash and strawberry 
tongue. The early use of serum usually arrests the process, principally 
by neutralizing the poison and thus depriving the organism of its 
principal aggressive weapon. Invasion of the tissues by the strepto- 
cocci, however, and the effects of their growth within the tissues, 
would not necessarily be prevented by antitoxic sera. 
Recently several observers^ have reported that persons may be sus- 
ceptible to one scarlet fever toxic filtrate, but less susceptible, or not 
susceptible to the filtrate of another strain: also the antitoxin specific 
for one strain may have little or no neutralizing value for the poison of 
another strain. This may mean either that the poison produced by 
various strains of scarlet fever streptococci has several antigenically 
specific fractions, in which case the value of an antitoxic serum would 
depend upon its content of the several specific antitoxic fractions, which 
would neutralize a majority of the toxic portions, or that there may be 
a group of scarlet fever streptococci, rather unlike serologically, much 
as the meningococci are unlike serologically. Thus far it is not possible 
to say with assurance which possibility is correct. Whatever the out- 
come may be, it is obviously necessary to be careful to utilize a suffi- 
ciently representative number of strains of streptococci to cover the 
possibilities in diagnosis, in immunization, and in the selection of anti- 
serum for therapeutic use. 
THE PNEUMOCOCCUS. 
Synonyms.— Micrococcus pasteuri, Diplococcus pneumoniae, Diplo- 
coccus lanceolatus, Streptococcus lanceolatus. 
Historical.— Although the pneumococcus was observed by Sternberg^ 
and independently by Pasteur^ in the blood of rabbits inoculated 
1 See Park, Rose and Spiegel: Jour. Immunol., 1925, 10, 829. 
2 Bulletin, National Board of Health, 1880-1881, 2, 781. 
3 Compt. rend. Acad. Sci., 1881, 92, 159. 
