| 1 | He had in fact intentionally used crystal methylene. | |
| 2 | But the patterns of methylation change as we grow older. | |
| 3 | Biologists have long known about the switches, which are clusters of atoms called methyl groups. | |
| 4 | This was accomplished in 2000 for most of the listed substances and in 2004 for methyl chloroform. | |
| 5 | However, thiomersal contains ethyl mercury, not methyl mercury, and ethyl and methyl mercury are quite different. |