1. Of twenty-nine so called normal urban adults tested, seven had less than two-fifths, three had two-fifths, two had three-fifths, eight had four-fifths and nine had a neutralizing power at least equal to the average of five batches of pooled convalescent serum.
2. Known contacts and avowed non-contacts were equally represented in the serums of low potency, but in the serums of higher potency, the known contacts predominated.
3. The pooled serums of known contacts and of non-contacts were respectively a little above and a little below half the strength of the average obtained for pooled convalescent serum.
4. Two series of early cases of poliomyelitis, the one treated with normal serum of proved protective power, the other with convalescent serum, showed no advantage of one type of serum over the other.