Some possible causes of congenital heart malformation.

Certain conditions found in human congenital heart disease are probably genetic in origin (Cockayne, 1938; Polani and Campbell, 1955), but sometimes they may be correlated with an environmental factor, namely the infection of the mother with rubella during early pregnancy. Thus there appears to be no single cause of congenital heart abnormality; sometimes genetic causes and sometimes environmental causes are implicated. The purpose of this article is to draw attention to certain general problems of heart development in vertebrate animals and to some recent experimental work on various vertebrates which may help towards a clearer understanding of the parts played by genetic and environmental factors in the production of congenital abnormalities of the heart.