THE NERVOUS SYSTEM OF AMPHIBIA 



311 



Tr.Des.V\ L.L.IX.X.Asc , , ,^ ^ 



Ent.V XL.L.VIIDes. Ent.L.L.IX.X 



Ent VII / / L.L.IX.X.Des 



Motor Column 



L.L.VII Des. 

 L L. VII Asc 

 TrAsc.V 



lEntVII 



R.VII.Vi 



Ent VIM 

 VIII Des 

 Tr Des.V 



Figs. 5 and 6 Projections from serial, transverse sections upon the sagittal 

 plane, of the sensory root fibers after they have entered the medulla oblongata, 

 in the coiled-reaction stage (fig. 5, No. 449) and in the early swimming stage 

 (fig. fi. No. 444). X 50. The most rostrally located Rohon-Beard cell of (he 

 spinal cord is represented in each case, and the ascending fibers of these cells 

 are shown as far cephalad as the root of the vagus nerve. The approximate 

 extent of the trigeminal root fibers caudad is indicated in solid black, while the 

 whole fiber system which I have called in the text the descending trigeminal tract 

 but which is made up in large part of neurones of the second order is indicated 

 in light lines about and beyond the root fibers proper. These figures are in a 

 measure schematic, as will be seen by comparing them with figures 38 to 70, 

 with wliich thev should be studied. 



