THE NERVOUS SYSTEM OF AMPHIBIA 203 



As might be expected, my observations add little to what has 

 been well known concerning the form and orientation of the giant 

 ganglion cells within the spinal cord. These features of the cell 

 have been exhaustively treated by Beard ('92, '96), Dahlgren 

 ('97), Studnicka ('95), Tagliani ('95), Sargent ('98), Johnston 

 ('00), Harrison ('01) and others. Some authors, including John- 

 ston, regard the cell process that is directed caudad in the cord 

 as a neurite, and therefore interpret the column as physiologically 

 descending as well as ascending. This may be true in the animals 

 studied by these investigators but there is no evidence of descend- 

 ing impulses in the column of the giant ganglion cells in Amblys- 

 toma embryos used in my work, and, in some cases, the periph- 

 eral fiber has been observed to arise from the descending process 

 of the cell. 



The lateral position of the cells in the more rostral portion of 

 the cord and their occurrence well forward in the medulla have 

 been observed by Johnston in Catostomus. He observes also 

 that in Catostomus and Coregonus the nuclei are differentiated 

 from the surrounding nuclei in their staining reaction, being 

 colored red while the surrounding nuclei are colored green with 

 the Ehrlich-Biondi triple stain. With the use of orange G, 

 Lyons blue and erythrosin as cytoplasmic stains my preparations 

 show the nuclei of the giant ganglion cells tinged shghtly with 

 these colors, in this manner differentiated from the nuclei about 

 them. 



My results add to the knowledge of these cells as regards 

 their central relations chiefly in demonstrating their organiza- 

 tion into an afferent conduction path which, through the greater 

 part of its extent if not through it all, is physiologically distinct 

 from the motor tract of the same side. My findings show that this 

 column of cells is an integral part of a reflex mechanism which 

 has the essential characteristic of the typical reflex arc of higher 

 vertebrates. 



Upon the peripheral relations of the giant ganglion cells there 

 has been some difference of opinion. Studnicka ('95) regards the 

 peripheral processes as rnotor upon the basis of his observation 

 that they terminate in the myotomes in Rana and Bufo. Tag- 



