Some names given to proteins and genes are extremely tedious but Lucina was taken by the idea of a sonic hedgehog. The sonic hedgehog gene (SHH) (could it be the gene rather than the hedgehog that’s sonic?) is the human homologue of a fruit fly gene that encodes inductive signals controlling development of the early embryo. It is on chromosome 7 (7q 36) alongside the gene (HPE3) implicated in some families with holoprosencephaly. In Chicago (

) a couple’s first two children had holoprosencephaly. Analysis of postmortem tissue samples from the more severely affected child showed an SHH nonsense mutation. This allowed preimplantation genetic diagnosis and the birth of a healthy child.

The upper limit set by the US Centres for Disease Control and Prevention for acceptable blood lead concentration has been lowered progressively since 1970 from 60 μg/dl (2.9 μmol/l) to 40 μg/dl, 30 μg/dl, 25 μg/dl, and (since the early 1990s) 10 μg/dl. Now it seems that there may be no completely safe blood lead concentration. Two studies reported side by side in the New England Journal of Medicine show effects at blood lead concentrations of less than 10 μg/dl. In the first study (2003;348:1517–26, see also perspective, ibid: 1515–16) 172 children had blood lead concentrations measured at 6, 12, 18, 24, 36, 48, and 60 months of age and Stanford Binet …