Abstract: Thin-layer chromatography, acetylation of reference and unidentified glucocorticosteroids, u.v. absorption and fluorescence induced in sulphuric acid were used to identify cortisol as the major free plasma glucocorticosteroid in the horse (Equus caballus), with cortisone and corticosterone as minor glucocorticosteroids. Deoxycorticosterone was also identified. The plasma ratio for free cortisol: cortisone: corticosterone was 16:8:0·5.The diurnal variation was determined for all three glucocorticosteroids. The highest levels of cortisol and corticosterone were found at 10.00 hr. (260 and 10·3 μg./100 ml., respectively) and the lowest concentration of cortisol at 02.00 hr. The highest level of cortisone occurred at 02.00 hr. (140 μg./100 ml.), and the lowest appeared at 16.00 hr. (65 μg./100 ml.). The maximum plasma concentration of the combined glucocorticosteroids was found at 10.00 hr. (395·3 μg./100 ml.), and the minimum at 20.00 hr. (219 μg./100 ml.).

Abstract: Our human intellect has resulted from an enormous leap in capacity above the level of monkeys and apes. Earlier, though, Old and New World monkeys' intelligence outdistanced that of other mammals, including the prosimian primates. This first great advance in intelligence probably was selected through interspecific competition on the large continents. However, even at this early stage, primate social life provided the evolutionary context of primate intelligence.
Two arguments support this conclusion. One is ontogenetic: modern monkeys learn so much of their social behavior, and learn their behavior toward food and toward other species through social example. The second is phylogenetic: some prosimians, the social lemurs, have evolved the usual primate type of society and social learning without the capacity to manipulate objects as monkeys do. It thus seems likely that the rudiments of primate society preceded the growth of primate intelligence, made it possible, and determined its nature.