The acoustic complex and its relations in the brain of the opossum (Didelphys Virginiana)

The following study of the central acoustic complex has been undertaken by the writer with the primary object of producing by reconstruction methods a simple three-dimensional picture of this apparatus, which would while of specific application to the opossum, yet have a larger value in the development of a clearcut conception of the morphology of this group of related structures in the mammalian brain as a type. The work of Sabin has established the value of this method of approach in the study of the anatomy of the brain; and it is hoped that this paper may prove a contribution to the field in which she has been so distinguished a pioneer. It may be added that this study is among the first of a series now in progress in this laboratory, whose eventual purpose is to present a morphological survey of the entire brain of Didelphys Virginiana. As a form in which to study the acoustic complex, the opossum offers several decided advantages, chief among which from the standpoint of this paper is the clearness with which units and relations stand out in a relatively primitive mammalian brain, but little obscured by the massive pontine nuclei and their connections which characterize the higher forms. Differentiation by the method of Weigert being especially satisfactory for a comparatively gross study at low magnification, the models weremade from such preparations. The drawings of individual sections serve the double purpose of elucidating the models, and of presenting certain important features whose incorporation in tho reconstructions was deemed inadvisable.