The method of whole embryo culture permits a variety of experimental m
anipulations to be performed on the mammalian embryo. When used in con
junction with mouse mutants, this technique can provide information on
the pathogenetic mechanisms underlying the development of birth defec
ts. To illustrate this approach, we review in vitro studies on the dev
elopment of embryos homozygous for the mutation curly tail (ct). These
studies have involved making repeated observations on individual embr
yos, performing surgical manipulations, applying environmental influen
ces and metabolic labelling. As a result of this work, we have now par
tially elucidated the developmental sequence of events that precedes t
he appearance of spina bifida in the ct mutant.