THE PRINCIPLES OF EMBRYOLOGY 467 
viz. that the lesion disturbed the chemico-physical equilibrium of an 
anatomically continuous (neuro-muscular or neuro-epithelial) chain 
of cells, by separating the non-nervous from the nervous, and that 
the changes occurring in denervated muscle, which I shall describe 
later (and possibly those in denervated skin), are in part due to the 
reciprocal chemico-physical disturbance effected in these tissues by 
their separation from the nervous tissues; also that the section of 
the posterior roots checked the development of those portions of 
them still attached to the spinal ganglia, because the chemico- 
physical equilibrium in those processes-is maintained not only by 
the spinal ganglion-cells, but also by the intra-spinal cells with which 
these processes are anatomically continuous.” 
What is seen so strikingly in the new-born animal can be seen 
also in the adult, and in Anderson’s paper references are given 
to the papers of Lugaro and others which lead to the same 
conclusion. 
These experiments seem to me distinctly to prove that the 
connection between the elements of the peripheral organ and the 
proximate neurone is more than one of contact. 
We can, however, go further than this, for, apart from the 
observations of Apathy, there is direct physiological evidence that 
the vitality of other neurones besides the terminal neurones is 
dependent upon their connection with the peripheral organ, even 
though their only connection with the periphery is by way of the 
terminal neurone. Thus, as is seen from Anderson’s experiments, 
section of the cervical sympathetic nerve in a very young animal 
causes atrophy of many of the cells in the corresponding intermedio- 
lateral tract, cells which I supposed gave origin to all the vaso- 
constrictor, pilomotor, and sweat-gland nerves. A still more striking 
experiment given by Anderson is the effect of the removal of the 
periphery upon the medullation of those efferent fibres which arise 
from these same spinal cells, for, as he has shown, section of the 
nerves from the superior cervical ganglion to the periphery in a very 
young animal delays the medullation in the fibres of the cervical 
sympathetic—that is, in preganglionic fibres which are not directly 
connected with the periphery but with the terminal neurones in the 
superior cervical ganglion. So also on the afferent side a sufficiently 
extensive removal of sensory field will cause atrophy of the cells of 
Clarke’s column, so that, just as in the case of the primary neurones, 
