58 Studies on tlie Neuroglia 



the neuroglia cells are generally vesicular and show usually only one 

 round or oval refractive granule, which stains deeply and of a purple 

 color. The amount of protoplasm found with these nuclei varies and 

 oftentimes is scarcely made out. Protoplasmic branches, when present, 

 are slender and short. Here and there are found nuclei, which stain 

 reddish-blue with protoplasm of the same color; such cells usually pre- 

 sent clearly-marked protoplasmic branches. The neuroglia fibers vary 

 much in thickness, stain a deep blue and are readily differentiated from 

 the protoplasm of the neuroglia cells and may be traced over and along 

 the borders of the neuroglia cells, often following the protoplasmic 

 branches when these are present. 



Frog. — In the frog, the greater proportion of the nuclei of the neu- 

 roglia cells are large, round, oval, or polymorphous and vesicular in 

 structure. They are often stained a purplish-blue color, in which case 

 they present a homogeneous appearance; when more bleached, they 

 show numerous small chromatin granules. Here and there, smaller 

 nuclei, staining deeply are also found and are more clearly seen in 

 longitudinal sections. Many free nuclei or nuclei with very little pro- 

 toplasm are found. The amount of protoplasm found varies greatly with 

 the different cells. The protoplasm usually stains a reddish-blue 

 or purplish-blue color. Branched neuroglia cells are found in the white 

 matter of the cord. 



The neuroglia fibers of the spinal cord of the frog are relatively very 

 large and are stained a deep blue color. The greater proportion of 

 these fibers run at right angles to the nerve fibers and in cross sections 

 may often be traced for relatively long distances. In cross sections, 

 not many fibers — usually not more than three or four — are seen in 

 relation with any one neuroglia cell or nucleus. The relation of the 

 neuroglia fibers to free nuclei and neuroglia cells is generally very 

 clearly made out; the neuroglia fibers being so large and of such defi- 

 nite course, we are enabled in both longitudinal and cross sections to 

 differentiate between these fibers and other structures. The neuroglia 

 fibers can usually be traced over or by the side of neuroglia cell nuclei 

 or neuroglia cells and are in no way interrupted by the protoplasm of 

 such cells. 



Conclusions. 

 These observations seem to warrant the following conclusions: 

 1. The neuroglia of the spinal cord of the dog, cat, rabbit, dove, tor- 

 toise and frog consists of neuroglia fibers and neuroglia cells. The 

 neuroglia fibers differ chemically from the protoplasm of the neuroglia 



