“Balster and Chait have been in the forefront of those studying questions related to tolerance. In their work with rehsus and squirrel monkeys, they found that the animals did in fact self-administer larger doses of the drug. In the study of two rhesus monkeys, the subjects voluntarily adminsitered PCP by lever pressing, at any time during a 24-hour period, for eight consecutive days. After this time, the monkeys were limited to an administration period of only four hours per day. Yet, the subjects continued to administer doses equal to those of the 24-hour period compressed within a severly limited time. Also cited is a study in which repeated use of PCP as an anesthetic for juvenile chimpanzees and adult baboons resulted in a shortened period of effectiveness and eventually,
