466 THE ORIGIN OF VERTEBRATES 
proved very difficult for physiologists to accept, but also Graham 
Kerr, in his latest papers on the development of Lepidosiren, has 
shown that there is continuity between the nerve-cell and the muscle- 
cell from the very first separation of the two sets of elements; in 
fact, Hensen is right and His wrong in their respective interpretation 
of the earliest stages of the connection between muscle and nerve. 
So also, it seems to me, the intimate connection between the meta- 
bolism of thé gland-cell, as seen in the submaxillary gland, and the 
integrity of its nervous connection implies that the connection 
between nerve-cell and gland-cell is of the same order as that between 
nerve-cell and muscle-cell. Graham Kerr also states in his paper 
that from the very commencement there is, he believes, continuity 
between nerve-cell and epithelial cell, but so far he has not obtained 
sufficiently clear evidence to enable him to speak positively on this 
point. 
Further, according to the researches of Anderson, the cells of the 
superior cervical ganglion in a new-born animal will continue to 
grow healthily as long as they remain connected with the periphery, 
even though entirely separated from the central nervous system by 
section of the cervical sympathetic nerve, and conversely, when 
separated from the periphery, will atrophy, even though still con- 
nected with the central nervous system. So, also, on the sensory 
side, Anderson has shown that the ganglion-cells of the posterior 
root-ganglion will grow and remain healthy after separation of the 
posterior roots in a new-born animal, but will atrophy if the peripheral 
nerve is cut, even though they are still in connection with the central 
nervous system. Further, although section of a posterior root in the 
new-born animal does not affect the development of the nerve-cells 
in the spinal ganglion, and of the nerve-fibres connecting the 
posterior root-ganglion with the periphery, it does hinder the 
development of that part of the posterior root connected with 
the spinal ganglion. 
These experiments of Anderson are of enormous importance, and 
force us, it seems to me, to the same conclusion as that to which he 
has already arrived. His words are (p. 511): “I suggest, therefore, 
that the section of peripheral nerves checked the development of 
motor and sensory neurones, not because it blocked the passage of 
efferent impulses in the first case and the reception of stimuli from 
the periphery in the second, but for the same reason in both cases, 
