G. Carl Huber 57 



clei and protoplasm of the neuroglia cells. In case of the branched 

 neuroglia cells, when the protoplasm is stained a purplish-blue, it is 

 now and then difficult and in certain cells quite impossible, in cross 

 sections of the cord, to differentiate between neuroglia fibers and pro- 

 toplasmic branches of neuroglia cells. It is often possible to trace with 

 the utmost clearness a neuroglia fiber along the side of a protoplasmic 

 branch of a neuroglia cell, along the side of or over the cell and by the 

 side of some other protoplasmic branch and away from the cell. At 

 other times, however, when a neuroglia fiber appears cut near the cell 

 body of a neuroglia cell or near one of its protoplasmic branches, it 

 appears as if the neuroglia fiber terminated in the cell. In longitudinal 

 sections of the spinal cord of the rabbit, the relation of the neuroglia 

 fibers to the cells under discussion is more readily made out. In such 

 sections, the neuroglia fibers can be readily traced over, under, and 

 around the neuroglia cells, even though at times the color of the neu- 

 roglia fibers is similar to that of the protoplasm of the cells. 



Dove. — I have had more difficulty in staining the neuroglia of the 

 spinal cord of birds than was experienced with the other vertebrates 

 studied. This is due to the fact that with the method used the neu- 

 roglia fibers seem to bleach out at about the same time as the neuroglia 

 cells and nerve fibers. When well stained, the color of the neuroglia 

 fibers is a light blue and, even in the most successful preparations, they 

 do not stand out as clearly as in the mammalia studied. In cross sec- 

 tions of the cord, the great majority of the neuroglia cells of the white 

 matter appear as branched cells with relatively large vesicular nuclei, 

 containing numerous chromatin granules. The protoplasm of such 

 cells often stains a reddish-blue or purplish-blue color. Here and there 

 in the white matter and more generally in the grey matter, free neu- 

 roglia cell nuclei are seen of vesicular structure and containing numer- 

 ous chromatin granules, or similar nuclei surrounded by very little 

 protoplasm. 



The neuroglia fibers in the spinal cord of the dove are relatively fine. 

 In longitudinal sections, it can be seen that they are independent of 

 the cell protoplasm of the neuroglia cells; in cross sections of the cord, 

 it is more difficult to see this, but in favorable sections, one can usually 

 trace the neuroglia fibers over or along the borders of the neuroglia 

 cells and gain the conviction that they are not the processes of these 

 cells. 



Tortoise. — The neurogliar tissue of the spinal cord of reptilia is quite 

 easily stained by the Benda method, the neuroglia nuclei and cells stain- 

 ing a brownish-red and the neuroglia fibers a deep blue. The nuclei of 



