. GROUP OF PYOGENIC COCCI. 
57 
past, especially among young children. In some epi¬ 
demics it has been as high as 90 per cent. The treat¬ 
ment with antimeningitis serum, however, has been 
attended with success, and the excessive mortality has 
been considerably reduced by its use. In this country 
this method of treatment was begun by Dr. Flexner 
and Dr. Jobling at the Rockefeller Institute in New 
York. The serum is made by injecting horses with 
slowly increasing doses of meningococci that have 
been killed by heat. The tolerance of the animals to 
the poison of the meningococci is gradually increased 
in this way until they are able to withstand many 
times the fatal dose. This tolerance depends upon an 
active immunity due to the formation within their 
bodies of protective substances that neutralize the 
poison. After eight or twelve months the horses are 
bled and the blood-serum containing the protective 
substances is used for treating patients sick with 
meningitis. 
The extended trial of the serum in a number of 
epidemics has shown that, the earlier it is used after 
the onset of the infection, the greater its curative 
value. For this reason it is customary to inject the 
serum immediately after the withdrawal of the cere¬ 
brospinal fluid by lumbar puncture, without waiting 
to determine the nature of the infecting organism. 
The serum should be given every twelve hours in 
severe cases until the spinal fluid becomes clear and the 
meningococcus is no longer present. The amount of 
serum to be given at one dose is dependent upon the 
Anti- 
menin- 
gitis 
serum 
