Abstract
Four [male] and 4 [female] guinea pigs, castrated, 2 of each prepubertally and 2 postpubertally, were given copulatory tests with [female][female] during a series of injns. of testosterone propionate and neutral oil. 5 animals showed increased sexual activity after the hormonal injs. 6 adult [male] guinea pigs were tested with [female][female] using the hurdle box technique for 2 mos. During this time 2 of the [male][male] were castrated and given testosterone propionate, and 2 others castrated but given no hormone. Castration caused a decrease in all measures. Hormonal injs. substantially restored all measures.