No. I .] DESMOGNA THUS FUSCA . 257 



The largest of these lie in the ventro-lateral angle of the 

 gray mass. Certain round cells or granules are present in the 

 dorsal horns ; between these and the epithelial and the large 

 nerve cells all kinds of transitions are found. He was not able 

 to demonstrate with satisfactory clearness a connection between 

 the fibers of the ventral roots and the large nerve cells, and 

 concludes that the central epithelial cells have a true nervous 

 function, basing his view especially on the fact that he found 

 fiber tracts coming from these cells into the ventral commissure 

 and dorsal roots. 



Roller (44) was perhaps the first to allude to the nervous 

 nature of these epithelial cells. He saw fibers going from 

 them to a group of nerve cells — the nidus of the glossopharyn- 

 geal nerve. 



General Histology. 



The retention of so many of the primitive and simple con- 

 ditions in the nervous system of a group so advanced as the 

 Amphibia renders it a very desirable class for study preparatory 

 to more specialized forms. The amphibian brain is regarded 

 by Edinger as the simplest in the vertebrate series. Here, it 

 is quite likely, will be found the key that will unlock the door 

 of many morphological and histological problems. A simplicity 

 of the general morphology of a part does not necessarily 

 involve a corresponding simplicity of its histology. Perhaps 

 these two conditions are exceptionally simplified in the Avi- 

 phibia for the neurocytes (nerve cells), and their relations 

 retain embryonic features to a remarkable extent when treated 

 by ordinary methods. The silver method reveals a more com- 

 plicated state of affairs, but as compared with similar structures 

 in other forms they are still relatively simple. The texture of 

 the neuraxis varies greatly even in closely associated genera, 

 and should be taken into account in "fixing" the material. 

 Experimentation is quite necessary, particularly with Golgi 

 preparations. With aquatic forms the tissue seems to be less 

 dense than with terrestrial. 



As has been stated by Oyarzun (39), much of the work done 

 on the amphibian nervous system has been in tracing out fiber 



