In the 1940s I was struck by reports about many apparently healthy middle-aged men who dropped dead instantly from heart attacks. The causes of these sudden deaths were unknown. I was interested to discover physio-chemical characteristics of individuals with predictive value for the occurrence of these fatal heart attacks. The discovery ofpreventive variables would point ways to prevent this disease. In order to find relationships between mode of life and susceptibility to heart disease contrasting populations had to be studied. Variety - not a high degree of homogeneity in culture and habits...