In the 19th century, descriptions of patients with disorders of higher cerebral functions were typically presented in a mixed series of children, adolescents, adults, and the elderly. There was no indication in the analysis or interpretation that age was thought to play a role in the signs or symptoms displayed, or in the prognosis. The role of age in the manifestation of language disorders only became explicit in the late 19th century in the elaboration of ideas regarding perinatal illnesses, developmental difficulties, and the emerging clinical category of "cerebral palsy" as evinced in the work of Bastian, Osler, Sachs and Peterson, and Freud. Their patient series studies afforded the opportunity to identify relations between age at symptom onset and patterns of language acquisition and impairment. These analyses contributed directly to the elaboration of hypotheses regarding localization of function, hemispheric specialization, and patterns of recovery. The factor of "age at symptom onset" would steadily assume even greater theoretical importance, as explanations of patterns of symptom co-occurrence, etiology, and prognosis were elaborated through the increasing appreciation of a developmental/maturational perspective.