What differentiates medical uses of cartograms most from political cartography is the mapping of clusters — individual cases of a disease or death which together might possibly be connected. One of the earliest cartograms thought to have been used for this purpose was reproduced in Figure 11. Figure 12e shows the distribution of cases of Wilm's tumour, a childhood cancer, identified in New York State between 1958 and 1962, drawn upon an equal land area map. Apparent clusters of cases have been marked on the map (Levison & Haddon, 1965: 56). In Figure 12f the same