Potency of nerve poisons

Many heavy metals such as lead and mercury may also harm the nervous system. It is not surprising that most insecticides are nerve poisons. They have LD50 values in mammals between 1 and 1000 mg/kg. 

It is evident that a typical nerve poison is selective because it only affects organisms having a nervous system, i.e., animals. 

The structure and functional elements of the nervous system in different animals are quite different, and some selectivity between animals from different groups is expected. On the contrary, various types of nerve cells have a rather 

---