Abstract
SUMMARY: A new autosomal recessive gene (cab, ‘cardiac abnormality’), which affects heart differentiation appeared spontaneously in our mouse colony. The affected homozygotes die approximately half a day prior to birth or at term, with the myocardium exhibiting vacuolation and large areas of mesenchyme-like cells. A significant finding in mutant foetuses is the lack of histochemically detectable glycogen.