746 



Nachdruck verboten. 



The Neuroglia Cells of the Walls of the middle Ventricle in the 



adult Dog. 



By Henby J. Beeklet, M. D., Baltimore. 

 (From the Pathological Laboratory of the Johns Hopkins University and 



Hospital.) 

 With 4 Figures. 



Two of the most distinguished, as well as recent, writers on the 

 histology of the central nervous system, have stated that in their opinion, 

 the embryonal supporting substance of the brain and spinal cord — 

 the ependymal neuroglia — almost entirely atrophies and disappears 

 in the adult mammal. To be more explicit: Cajal x ) states of birds 

 and mammalia "that the ependymal epithelial cells of brain and spinal 

 cord, lose their stems as well as their branching processes, and no 

 longer reach the periphery, but end in the white and gray substances. 

 The epithelial neuroglia only retains its embryonal type in two organs, 

 the olfactory mucous membrane and the retina". The other cited 

 writer, Koelliker 2 ), speaking of his attempts to obtain a successful 

 staining of the ependymal cells of the spinal cord in full grown ani- 

 mals, adds, after reciting his want of success: "I presume therefore 

 that the ependymal fibres are only present in the adult in a very 

 stunted condition, and it is not to be supposed that they run to the 

 outer surface of the cord". 



After reading these statements, it was somewhat of a surprise to 

 find in a recent study of the infundibular region of the adult 

 dog, most beautiful and well developed specimens of the earliest 

 kinds of ependymal neuroglia, extending from all portions of the in- 

 ferior and middle regions of the cavity of the third ventricle, and 

 reaching to the periphery, all portions, bodies, branches, tentacles, and 

 sub-pial endings being readily distinguishable. 



The results in this direction were obtained through the agency 

 of my modification of the silver stain 3 ), that is by previous immersion 



1) Cajal, Neue Darstellung vom hist. Bau des Centrain ervensystems. 

 Arch. f. Anat. u. Phys., 1893. 



2) Koellikee, Gewebelehre, 6. Aufl., 1893. 



3) Tide this Centralblatt, Nos. 23—24, 1893. 



