Studies on the Examination of the Safety of Inactivated Poliomyelitis Vaccines. Report No. 5. Pathomorphological Alterations in the Central Nervous System of Rhesus Monkeys (Macaca rhesus) and Long-Tailed Monkeys (Cercopithecus aethiops) after Intra cerebral and Intralumbar Inoculation with Partially Inactivated Poliomyelitis Virus Types I, II, and III.