The excess accumulates in place, sometimes to hazardous depths. A stock is the term for any entity that accumulates or depletes over time. Much developmental trauma accumulates gradually over time. As more damage accumulates, the risk for cancer increases. This insoluble protein accumulates inside neurones forming inclusions called Lewy bodies. Let-7 accumulates in human tissues during the course of aging. Eventually much gas accumulates and becomes pressurized. Fluid accumulates in the upper ventricles, causing hydrocephalus. In cholestasis, bile accumulates in the hepatic parenchyma. When peat accumulates, bogs and fens arise. Free cytotoxic heme accumulates in the parasites, causing death. Free cytotoxic heme accumulates in the parasites, causing their deaths. Peat usually accumulates slowly at the rate of about a millimetre per year. Instead, it accumulates, primarily in the viscera, although also in the muscle tissue. Over time dust accumulates on household surfaces.