In order to decide whether the rabbit method or the rhesus monkey test is better suited for routine vaginal tolerance tests of spermicidal preparations, combined trials employing both techniques were carried out in the two laboratories in which the tests had been developed.A`double-blind' experimental design was used in which three unknown, coded compounds were tested jointly in both laboratories and evaluated independently and reciprocally after transatlantic exchange of the resulting histological material. Both test methods and the scoring systems employed in the assessment of findings are described and illustrated by representative photomicrographs.There was good agreement between both methods for two of the three preparations tested. For the third preparation, the rabbit test results were more consistent with the available clinical data than those of the monkey test.It was concluded that the rabbit technique is more sensitive than the monkey test. Since it has several obvious practical advantages over the latter, it is proposed that the rabbit vagina test should be generally adopted as the standard method for establishing the local tolerance of new spermicidal preparations for vaginal use.

Observations are recorded on the placenta of the guinea-pig at the 65th day of pregnancy. Placental weight is inversely related (a) to number of foetuses in the same horn of the uterus, and (b) to number of foetuses in the other horn. In litters with unequal numbers of foetuses in the two horns, placental weight is greater on the side with the smaller number. These observations are consistent with those previously recorded on foetal weight [Eckstein & McKeown, 1955]. Nevertheless, the variation in placental weight does not wholly account for the variation in foetal weight. Even when attention is restricted to foetuses with placentae of the same weight, foetal weight appears to reflect both a general effect, due to litter size and independent of distribution between the horns, and (less certainly, because of small numbers), a local effect, determined by contiguity of foetuses within the same horn. The possible significance of the last two observations is discussed.It has been shown that weight of the placenta, like weight of the foetus, is inversely related to the number of individuals in a litter.

No abstract

No abstract

SUMMARY In twenty-nine guinea-pigs examined on the 65th day of their first pregnancy, litter size was positively correlated with maternal weight at conception. This association was independent of maternal age; there was no significant correlation between size and age after correction for weight. Similar results were obtained in 113 animals reported by Ibsen 1928]: a substantial positive correlation between litter size and weight (0·43) was independent of both age and parity, but there was only a trivial correlation with age (0·07), and a negative correlation with parity (−0·16) after correction for weight. Correlations between number of corpora lutea and weight (0·32, after correction for age) and between number of corpora and age (−0·17, after correction for weight) in twenty-eight of the twenty-nine animals, suggest that the association between litter size and weight is determined mainly by a positive correlation between weight and the number of ova produced.