G. Carl Hiiber 59 



cells— as shown by differential staining — but this difference is not 

 equally well marked in all the forms studied. In the animals studied, 

 this chemical difference between the protoplasm of neuroglia cells and 

 neuroglia fibers is most marked in the dog, cat and tortoise, less so in 

 the rabbit and frog and least in the dove. 



II. The neuroglia fibers may be regarded as intercellular structures, 

 as they bear no constant relation to the great majority of the cell nuclei 

 or neuroglia cells observed. 



III. By reason of the fact that the protoplasm of the neuroglia cells 

 is stained by the Benda method, this method has been helpful in show- 

 ing that there are certain neuroglia cells, usually possessing protoplas- 

 mic branches, the neuroglia fibers of which are not completely sepa- 

 rated from the protoplasm, but are in continuity with it or even pass 

 through it. That such neuroglia fibers are not simply processes of the 

 cells is usually clearly shown by their chemical reaction — behavior to- 

 ward stains — and by the fact that such fibers may generally be traced 

 over, under, or along the sides of such cells without suffering inter- 

 ruption. That such cells are normal constituents of neurogliar tissue 

 is shown by the fact that they occur in the spinal cord of the four 

 classes of vertebrates studied. 



IV. These observations present no evidence which would go to con- 

 firm V. Kolliker's hypothesis concerning the structure of neuroglia cells 

 — namely a nucleated cell body with differentiated cell-plate, from which 

 arise processes, the neuroglia fibers. Cross and longitudinal sections 

 of the spinal cord of the animals studied show no such relation of 

 neuroglia fibers and neuroglia cells. These observations cannot be 

 used in confirmation of Eeinke's views of the structure of the neuroglia. 

 The branched neuroglia cells seen by me bear no resemblance to the 

 astrocytes or astroblasts, as seen in the chrome-silver preparations with 

 which I am familiar, nor do they resemble the figures given by Eeinke. 

 In my own preparations, the neuroglia fibers very generally follow the 

 course of the protoplasmic branches of the neuroglia cells. 



V. The observations here presented strengthen materially the posi- 

 tion held by Weigert and Mallory as to the structure of neuroglia tis- 

 sue, as well as by others who may have used their methods or modifi- 

 cations thereof in the study of neuroglia, and extend their observations 

 to cover the more important vertebrate classes. 



Finally the following quotation from Pollack's article may serve to 

 emphasize the further advantages of the method used by me: " Ange- 

 sichts des Umstandes aber, dass wir des Thierexperimentes nicht 

 entrathen konnen, da wir ja am Menschen keine Versuche mit experi- 



