The localization of sulfur-35 administered intraperitoneally as sodium sulfate to 7-day-old rats was determined by radioautography of sections of humeri and tibia-knee-femur combinations removed 24, 48, 96, 216, and 290 hours after injection of this isotope. Radioautography of sections of bone and cartilage that had been fixed in formalin indicated that the tracer isotope was present throughout...