Ross Granville Harrison 131 
of the vagus is ultimately drawn out to this enormous length. ‘The ob- 
servations of Kerr“ upon the motor nerves of Lepidosiren are, in my 
opinion, capable of a similar interpretation and are a valid support of 
Hensen’s view only in the above modified sense. In other words, the ner- 
vous connection, though formed very early, is by no means primary. 
The results of the foregoing may be summarized as follows: The axis 
eylinder of the nerve fiber is the outgrowth of a single ganglion cell, with 
which it remains in continuity throughout life. It grows gradually from 
the center towards the periphery establishing secondarily connection with 
its end organ. The other elements, the cel!s of Schwann, which are 
found upon the developing nerve have nothing to do with its genesis, 
though they may play an important part in the nutrition and protection 
of the fibers. 
1 J. Graham Kerr, Trans. Roy. Soc. Edinburgh, Vol. XLI, 1904. 
