RESORPTION IN GUINEA PIGS AS ESTIMATED BY COUNTING CORPORA LUTEA - PROBLEM OF TWINNING

Normal pregnant guinea pigs were killed on gestation days 12–20 and examined for implantation sites and resorbing embryos. Their ovaries were removed and serially sectioned, and the functioning corpora lutea counted for comparison with the number of conceptuses. It was found that a single corpus luteum was associated with two implantation sites with a frequency of 9.55%. Embryonic loss prior to implantation was 12.6% and the value for resorption following implantation varied from 5.8 to 7.2% depending on the time of killing and the method employed for determining resportion. A count of functioning corpora lutea facilitated the determination of embryonic loss prior to implantation, but offered little advantage over simpler techniques for determining resorption after implantation. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company