In the first stage of radiation sickness, the victims usually vomit repeatedly, run a fever, and develop an abnormal thirst. Then, after a few hours or days, there is a deceptively hopeful period of the remission of symptoms, called the latency period, which lasts between one and four weeks. Radiation attacks the reproductive function of cells, and those that reproduce most frequently are therefore the most vulnerable. Among these are the bone-marrow cells, which are responsible for the production of blood cells. During the latency period, the count of white blood cells, which are instrumental in fighting infection, and the count of platelets, which are instrumental in clotting, drop precipitously so that the body is poorly defended against infection and is liable to hemorrhaging.
Radioactivity penetrates the environment in many ways.
The two most important components of radiation from fallout are gamma rays, which are electromagnetic radiation of the highest intensity, and beta particles, which are electrons fired at high speed from decaying nuclei. Gamma rays subject organisms to penetrating whole-body doses and are responsible for most of the ill effects of radiation from fallout. Beta particles, which are less penetrating than gamma rays, act at short range, doing harm when they collect on the skin or on the surfaces of plants. Effects on Animals . In a full-scale attack, which would create levels of radiation around the country averaging more than 10,000 rads, most of the mammals in the United States would be killed off.