Abstract
Strain differences among inbred mice is demonstrated for the relative amounts of peritoneal ascites fluid induced by the injection of Freund's adjuvant and antigen. Females tend to produce more fluid than males; the lower level in males is attributable to the action of male hormone. Both genetic and epigenetic factors are determinants in the response levels; genetic factors differentiate the inbred strains of mice, epigenetic factors underlie the variations within a strain and the difference between sexes.