Abstract
Prenatal and precolostral newborn quokkas, S. brachyurus, had no immunoglobulins in their serum. Immunoglobulins were not detected in the yolk-sac fluid, the amniotic fluid, or the allantoic fluid, but were present in the uterine fluid, the colostrum, and milk whey. Immunoglobulins were present in the serum of neonatal quokkas that had suckled for at least 24 hr. Initial immunization of a female with Salmonella adelaide flagella and bacteriophage 0 x 174 antigen resulted in high titres of antibodies in her blood 1 week later, but there was a lag of less than 1 week before anti-S. adelaide agglutinins and a lag of 2 weeks before antiphage antibodies were detectable in the serum of the suckling pouch young. A further delay of 2 weeks occurred before serum antibody titres were as high in pouch young as they were in the mother. At no time in development did antibody titres in the sera of pouch young exceed those of the mother. The ability to absorb antibody in the gut ceased 2-3 weeks after the 6-month-old young left the pouch.