Complex sentence: Southard asked him to design mental testing techniques applicable to patients at the psychopathic hospital, and Yerkes received a half-time appointment at Boston Psychopathic with Southard from 1913 to 1917.
Split into simpler sentences: Southard asked him to design mental testing techniques that could be applied to patients at the psychopathic hospital. Yerkes was given a half-time appointment at Boston Psychopathic with Southard from 1913 to 1917.