THE ACOUSTIC COMPLEX AND ITS RELATIONS IN 

 THE BRAIN OF THE OPOSSUM (DIDELPHYS 



VIRGINIANA) 



JOHN H. STOKES 

 From the Anatomical Laboratory oj the University of Michigan 



POUKTEEN FIGURES 



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 clear- 

 cut conception of the morphology of this group of related struc- 

 tures 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 dis- 

 tinguished a pioneer. It may be added that this study is among 

 the first of a series now in progress in this laboratory, whose even- 

 tual 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 connec- 

 tions which characterize the higher forms. Differentiation by the 

 method of Weigert being especially satisfactory for a compara- 

 tively gross study at low magnification, the models were made 

 from such preparations. The drawings of individual sections 

 serve the double purpose of elucidating the models, and of pre- 

 senting certain important features whose incorporation in the 

 reconstructions was deemed inadvisable. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 12, NO. 4 

 JANUARY, 1912 



401 



