Yolk-sac Perfusion of Chick Embryos

Summary

1) Yolk-sac perfusion, a new technic which permits the continuous or intermittent passage of fluids through the yolk sac of 4-day chick embryos, has been used to study survival of chick embryos perfused with varying concentrations of yolk. 2) When a yolk-free, balanced salt solution was perfused for 8 hours at 0.5 ml/min., alternating with 8 hours of non-perfusion, almost all embryos died between 20 and 45 hours. Survival time increased in proportion to yolk concentration up to 8% yolk, at which level some embryos were alive 96 hours after perfusion was started. 3) The defined medium was not a satisfactory yolk substitute. The combination of medium and dilute yolk resulted in even poorer survival than that obtained with yolk alone, thus indicating an imbalance or toxicity of one or more components of the medium.