Diagnosis of Abortive Cases of Poliomyelitis 55 
virus of poliomyelitis in vitro. Their case was a child which suf- 
fered a clinically obscure, mild illness about the same time that 
another child of the same family suffered a frank attack of polio- 
myelitis. 
We have undertaken a similar demonstration in nine suspected 
abortive cases of poliomyelitis selected from a much larger number 
observed during an epidemic of acute anterior poliomyelitis in 
Iowa in the summer of 1910. Special interest is attached to these 
cases because of the mildness of their symptoms, the frequency 
of similar cases and their epidemiological relation to cases of frank 
poliomyelitis. 
The sera of these nine cases were tested for immune bodies as 
follows: One half cubic centimeter of each serum was mixed with 
an equal volume of a 5 per cent, emulsion (filtered through paper) 
of fresh spinal cord from a monkey in the acute paralytic stage 
of poliomyelitis following inoculation with virus (M.G.) kindly 
furnished by Dr. Simon Flexner, of the Rockefeller Institute. 
To each mixture was added 0.1 c.c of fresh serum from a normal 
adult. As controls, we used the serum of a frank case of polio- 
myelitis and of a normal adult. The mixtures were allowed to 
stand 1 hour at 27 0 C. and 20 hours at 15 0 C. One half cubic 
centimeter of each mixture was then injected intracerebrally into 
a monkey (Macacus rhesus). The two control monkeys receiv- 
ing the mixture of normal serum and virus developed typical 
poliomyelitis on the tenth and twelfth day respectively. Three of 
the monkeys receiving the serum from suspected abortive cases 
also developed poliomyelitis. 
The monkeys receiving the serum from the other six suspected 
abortive cases, and from the frank case of poliomyelitis have all 
remained well (78 days). 
We then repeated the test, using the serum of the three sus- 
pected abortive cases which had failed to show immune properties 
in the first experiment; and for controls, using five specimens of 
normal human serum (three adults and two children). In this 
series we altered the proportion of serum and virus to the extent 
that we used a one per cent, emulsion of fresh spinal cord, all 
other conditions remaining the same. In this series poliomyelitis 
developed in only two of the controls, and in one of the monkeys 
