Hardesty, spinal Nerves of the Frog. 



93 



I. Scheme II is intended to illustrate a probability that 

 on approaching maturity the peripheral process of a spinal 

 ganglion cell (b) becomes medullated first. The mature cell 

 {a) has sent a process in both directions and consequently in 



6 



that case a fiber would be counted on both sides of the gang- 

 lion. Direct histological evidence in favor of Scheme II is lack- 

 ing. Some observations however may be considered as having 

 an indirect bearing upon this point : 



In addition to the work of Wagner ('48) on the spinal 

 ganglia of fishes, the more recent observations of van Gehuchten 

 ('91), KoUiker ('93), Cajal ('93 and '94), Lenhossek ('95) and 

 Dogiel ('97), made chiefly upon foetal material, indicate that 

 the central process of the T-fiber is often much thinner than the 

 peripheral one. And the observations of Ambronn and Held 

 ('96) seem to indicate that as a whole the peripheral system is 

 medullated before the central and thus perhaps the peripheral 

 process of the spinal ganglion cell acquires its medullary sheath 

 before the central one which goes to form the dorsal root. 



2. Scheme III illustrates a possibility of one source of 

 the excess of fibers distal to the spinal ganglion. This sugges- 



6 



tion was offered by Buhle ('98). It is based upon the fact that 

 in certain cases a splitting of the processes has been observed 

 within the spinal ganglion. 



